POTASSIUM DYNAMICS AND RESPONSE TO APPLIED POTASSIUM IN PADDY-PADDY AND SUNFLOWER- BENGALGRAM CROPPING SYSTEM UNDER VERTISOLS IN TBP COMMAND AREA

Transcription

1 POTASSIUM DYNAMICS AND RESPONSE TO APPLIED POTASSIUM IN PADDY-PADDY AND SUNFLOWER- BENGALGRAM CROPPING SYSTEM UNDER VERTISOLS IN TBP COMMAND AREA Thesis submitted to the University of Agricultural Sciences, Dharwad in partial fulfillment of the requirement for the degree of DOCTOR OF PHILOSOPHY IN SOIL SCIENCE By K. NARAYANA RAO DEPARTMENT OF SOIL SCIENCE AND AGRICULTURAL CHEMISTRY COLLEGE OF AGRICULTURE, DHARWAD UNIVERSITY OF AGRICULTURAL SCIENCES DHARWAD JUNE, 2011

2 ADVISORY COMMITTEE DHARWAD JUNE, 2011 (N.A. YELEDAHALLI) CHAIRMAN Approved by : Chairman : Members : (N.A. YELEDAHALLI) 1. (G.S. DASOG) 2. (M.N. SREENIVASA) 3. (H.T. CHANNAL) 4. (S.I. HALIKATTI)

3 CONTENTS Sl. No. Chapter Particulars CERTIFICATE ACKNOWLEDGEMENT LIST OF TABLES LIST OF FIGURES LIST OF PLATES 1. INTRODUCTION 2. REVIEW OF LITERATURE 2.1 Forms and distribution of potassium in soils and their relationship with soil properties 2.2 Dynamic equilibrium among different forms of soil potassium 2.3 Potassium reserves in textural fractions of soil 2.4 Potassium releasing power of soils 2.5 Potassium fixation capacity of soils 2.6 Response of crops to potassium application 2.7 Uptake by crops 2.8 Mineralogy of clay fraction in relation to potassium bearing minerals 3. MATERIAL AND METHODS 3.1 Field experiments 3.2 Laboratory studies 3.3 Determination of various forms of soil potassium 3.4 Potassium reserves in textural fractions of soil 3.5 Potassium fixation capacity of soils 3.6 Clay mineralogical studies 3.7 Statistical analysis Conud

4 Sl. No. Chapter Particulars 4. EXPERIMENTAL RESULTS 4.1 Physico-chemical properties of the surface and subsurface soils collected from cropping sequence 4.2 Forms and distribution of potassium in soils of cropping sequence 4.3 Response of crops to K application in cropping sequences 4.4 Uptake of K by crops in the cropping sequences 4.5 Potassium Balance sheet 4.6 Potassium fixation capacity of soils of experimental site in both the cropping sequences 4.7 Potassium reserve in different size fractions of the soil experimental plots of both the cropping sequences 4.8 Clay mineralogy of soil of experimental site of both the cropping sequences 5. DISCUSSION 5.1 Physico-chemical properties of the soils 5.2 Forms and distribution of potassium in soils of paddy-paddy and sunflower-bengalgram sequences 5.3 Response of crops to potassium application in cropping sequence 5.4 Uptake of potassium by crops 5.5 Potassium fixation studies 5.6 Potassium reserves in textural fractions 5.7 Mineralogy of the clay fraction 6. SUMMARY AND CONCLUSIONS REFERENCES

5 LIST OF TABLES Table No. Title 1. Meteorological data of the Raichur district for the years and recorded at Agro-meteorological Services Unit, MARS, Raichur 2. Details of the soil samples collected from villages for study under paddypaddy cropping sequence 3. Details of the soil samples collected from villages for study under Sunflowerbengalgram cropping sequence 4. Initial soil characteristics of experimental plot of paddy-paddy cropping sequence at Kasbe camp village 5. Initial soil characteristics of experimental plot of sunflower-bengalgram cropping sequence at Gabbur village 6. Textural analysis of soils from paddy-paddy cropping sequence under vertisols in TBP Command area 7. Chemical properties of soil samples from paddy-paddy cropping sequence under vertisols in TBP Command area 8. Textural analysis of soils from sunflower-bengalgram cropping sequence under vertisols in TBP Command area 9. Chemical properties of soil samples from sunflower-bengalgram cropping sequence under vertisols in TBP Command area 10. Distribution of different forms of K in soil samples of paddy-paddy cropping sequence under vertisols in TBP Command area 11. Distribution of different forms of K in soil samples of sunflower-bengalgram cropping sequence under vertisols in TBP Command area 12. Effect of potassium management practices on growth and yield of kharif paddy under vertisols in TBP Command area 13. Effect of potassium management practices on growth and yield of rabi paddy under vertisols in TBP Command area 14. Effect of potassium management practices on growth and yield of kharif sunflower under vertisols in TBP Command area 15. Effect of potassium management practices on growth and yield of rabi bengalgram under vertisols in TBP Command area 16. Effect of potassium management practices on uptake of K by paddy in paddy-paddy cropping sequence during Conud

6 Table No. Title 17. Effect of potassium management practices on uptake of K by paddy in paddy-paddy cropping sequence during Effect of potassium management practices on uptake of K by sunflower and bengalgram under sunflower-bengalgram cropping sequence under vertisols in TBP command area 19. Effect of potassium management practices on uptake of K by sunflower and bengalgram under sunflower-bengalgram cropping sequence under vertisols in TBP command area 20. Potassium balance sheet for paddy-paddy cropping sequence (2 years) under vertisols in TBP Command area 21. Potassium balance sheet for sunflower-bengalgram cropping sequence (2 years) under vertisols in TBP Command area 22. Potassium fixation capacity of soils of experimental sites under vertisols in TBP Command area 23. Potassium reserves in various size fractions of soils from experimental sites under vertisols in TBP Command area 24. Minerological composition of soil clays from experimental sites under vertisols in TBP Command area 25. Simple correlation coefficients between selective soil properties and different K forms of surface soil samples under paddy-paddy cropping sequence 26. Simple correlation coefficients between selective soil properties and different K forms of surface soil samples under sunflower-bengalgram cropping sequence

7 LIST OF FIGURES Figure No. Title 1. Meteorological data of the Raichur district for the years and recorded at Agro-meteorological Services Unit, MARS, Raichur 2. Plan of layout of the field experiment 3. X-Ray diffractograms of 0-15 cm soil clay sample of paddy-paddy cropping sequence collected at Kasbe camp 4. X-Ray diffractograms of cm soil clay sample of paddy-paddy cropping sequence collected at Kasbe camp 5. X-Ray diffractograms of cm soil clay sample of paddy-paddy cropping sequence collected at Kasbe camp 6. X-Ray diffractograms of 0-15 cm soil clay sample of sunflowerbengalgram cropping sequence collected at Gabbur camp 7. X-Ray diffractograms of cm soil clay sample of sunflowerbengalgram cropping sequence collected at Gabbur camp 8. XRD of cm soil clay sample of sunflower-bengalgram cropping sequence collected at Gabbur camp 9. Effect of potassium management practices on grain and straw yield of paddy under Paddy-Paddy sequence 10. Effect of potassium management practices on yield of sunflower and bengalgram crops under sunflower-bengalgram sequence 11. Effect of potassium management practices on pooled grain and straw yields of crop under different cropping sequence 12. Effect of potassium management practices on potassium uptake by paddy under paddy-paddy sequence 13. Effect of potassium management practices on potassium uptake by crops under Sunflower-Bengalgram sequence

8 LIST OF PLATES Plate No. Title 1. General view of the experimental plot of paddy crop 2. General view of the experimental plot of sunflower crop 3. General view of the experimental plot of bengalgram crop

9 1. INTRODUCTION Among the major plant nutrients potassium is the most abundant element in soils. It constitutes an average of 1.9 per cent of the earth s crust. Potassium is known to exist in structural (mineral), non exchangeable (fixed), exchangeable (available) and water soluble forms. The latter three forms are in dynamic equilibrium with each other. Because of its ready solubility in soil, it can easily move to exchange sites on clay colloids, get into the soil solution, diffuse into plant roots by absorption, taken up in the plant system by nutrient uptake or leach out from plant tops and roots back into the soil, be converted into exchangeable and non exchangeable forms or leach out of the soil with percolating water. Potassium is the third most nutrient element after nitrogen and phosphorus required for crops, which has assumed a significant importance as a fertilizer in most of the countries. But its consumption is still lower than N or P, because of the response ratio which is fairly lower (1 kg K 2 O: 5 kg grain) than N (1 kg N:10 kg grain) or P (1 kg P 2 O 5 :7 kg. grain) (Mahendra Singh and Mittal, 1983). The importance of K in Indian agriculture is increasing with the passage of time. Crop responses to K application are frequent and pronounced. The soil potassium gets depleted with the use of high yielding varieties, increase in cropping intensity and more use of nitrogen and phosphatic fertilizer. The results of long term fertilizer experiments in India revealed that by growing crops without K for longer periods, the available K status of soils decreases and needs immediate replenishment. The imbalanced and inadequate application of fertilizers has serious repercussions on efficacy of the applied fertilizers. Balanced, integrated and efficient use of fertilizers, among other inputs, has tremendous potential to increase crop productivity provided the problems related to soil health, fertilizer use efficiency and declining crop response ratio are addressed appropriately. Development of practices to improve the efficiency of nutrient requires an understanding on the fate of the applied nutrients and their effect on crop production. The continuous and adequate nutrition of K to plants depends not only on the amount of plant available K in soils but also on its rate of release into the soil solution. Vertisols and associated soils with relatively low level of this ratio have available K but low to medium nonexchangeable K, which under long term cropping may get depleted faster. In soils with low levels of both exchangeable and non exchangeable K, potassium application must be done to realise the yield potential of crops (Srinivas Rao et al., 2010). Under intensive cropping in the absence of K fertilization, initially exchangeable K in the soil contributes to the plant nutrition but with further cropping exchangeable K attains certain minimal level and thereafter, plant K removal from soil. The contribution of non exchangeable K to K uptake are synonymous and accounts for upto per cent of the total plant uptake. Due to larger contribution of non exchangeable K to plant K, low crop response to applied K have been reported in soils with low exchangeable K. The release of K from clay minerals may be very slow process depending upon the weathering stage of the minerals. The release of K from clay minerals becomes the most important aspect as for as K nutrition of the plant is concerned. It has been generally reported that potassium content of Indian soils is considerably higher than nitrogen and phosphorus, and consequently the response of crops to K application is low. Controversy still exists over the need for K fertilization of crops in some soils. Nevertheless, depending upon the nature of soil, climate, season, crop needs, cropping system and varieties characteristics the response of crops to K application might vary. But with cultivation of high yielding, fertilizer responsive varieties coupled with intensive and multiple cropping programmes under irrigated farming demand heavy use of balanced fertilizers including substantial amount of K has been strongly felt. Hence, to formulate sound fertilizer recommendation of K for different cropping systems, the knowledge of its status, supplying power, fixation capacity etc., in different soils is essential. The paddy-paddy and sunflower bengalgram are the two important and dominant cropping systems of this region-2 of North Eastern Dry Zone of Karnataka, followed in dominant black soils under irrigated and rainfed conditions.

10 Paddy is grown in an area of 0.44 m ha with a production of 2.07 mt and productivity of 5347 kg ha -1, sunflower is grown in an area of 0.26 m ha, with a production of 0.12 mt and productivity of 550 kg ha -.1. The area under bengalgram is 0.28 m ha with a production of 0.18 mt and productivity of 646 kg ha -1 (Anon., 2009). Despite enormous growth of these cropping systems in this region during past few years, there are reports of stagnation in the productivity of these crops, with possible decline in production have raised doubts on sustainability of these cropping systems in future. The farmers of this region lacks the knowledge of balanced nutrition, assuming that these soils are rich in potassium, they are applying heavy doses of nitrogen (200% more than the recommendation) and phosphorus as per recommended dose and little (about 25% of` recommended dose) application of potassium for paddy under irrigated condition. In sunflower and bengalgram cropping sequence, under rainfed condition, farmers are using less than the recommended dose of N and P (50-75%) without K application. This imbalanced nutrition has resulted decline in soil fertility status, over mining of nutrients from soil, decrease in response to nutrients application, build up of pests and diseases and decline in yields of the crops from past few years. Hegde and Sudhakar babu (2001) reported a negative balance for potassium in all agro-climatic zones of Karnataka with a net negative balance of 0.39 mt. The N and P usage was in excess of their crop removal. Although attempts have been made to study potassium status and its dynamics in different soils of Karnataka, the information on status of potassium and its dynamics and uptake pattern in dominant black soils of the region under paddy-paddy and sunflowerbengalgram cropping systems is lacking. In view of the facts presented above, a field study was undertaken on the rates of potassium depletion as a result of continuous cropping with varied level of potassium application in paddy-paddy and sunflower-bengalgram cropping systems under dominant black soils of North Eastern Dry Zone with the following broad objectives 1. To assess the effect of different cropping systems on changes in status of different forms of potassium. 2 To study the contribution of non exchangeable and sub soil potassium to crop nutrition in different productivity system. 3 To study the potassium fixation capacity of soil and 4 To relate the mineralogy of soil to potassium availability.

11 2. REVIEW OF LITERATURE In the present day agriculture, potassium is a major plant nutrient in crop production. It plays a pivotal role in growth and development of crop plants. It is often absorbed by plants in amounts equal to or greater than nitrogen, which has drawn the attention of several research scientists to understand its behavior in different soils and study the crop response to applied potassium fertilizers. Lots of research work have been carried out to know its distribution and transformation in different soils under different cropping systems, its fixation, release and the availability indices for potassium for predicting crop response to application of potassic fertilizers under field condition. The importance of potassium in agriculture is being increasingly recognized in India. In order to maintain soil fertility and productivity, to prevent land degradation and desertification and alleviate soil nutrient mining, nutrient removed by crops must be replenished. A thorough understanding of potassium status in the soil could be possible only by measurement of several parameters (Grimme and Nemeth, 1978) that are related to its different forms in the soil solution and the solid phase of the soil. Keeping such issues in view, literatures related to the present investigation are reviewed under the following headings. 2.1 Forms and distribution of potassium in soils and their relationship with soil properties 2.2 Dynamic equilibrium among different forms of soil potassium 2.3 Potassium reserves in textural fractions of soil 2.4 Potassium releasing power of soils 2.5 Potassium fixation capacity of soils 2.6 Response of paddy, sunflower and bengalgram to potassium management 2.7 Potassium uptake by crops 2.8 Mineralogy of clays in relation to K bearing minerals 2.1 Forms and distribution of potassium in soils and their relationship with soil properties The forms of K in soils are in the order of their availability to plants and microbes are solution, exchangeable, non-exchangeable and mineral potassium. Potassium extracted by neutral normal ammonium acetate solution (NN NH 4 OAc) has been universally considered as available K, which includes both water soluble and exchangeable forms of soil K. More than 90 per cent of the available K in soil exists in exchangeable form, which often constitutes about one per cent of the total K in fertile loam soil (Attoe and Trough, 1945). Potassium which is present in soil solution under normal field moisture conditions and relatively unbound by cation exchange forms is termed as water soluble potassium (Reitemeir, 1951). Water soluble K in mineral soil is about one per cent of exchangeable K. Water soluble K in Indian soils under average conditions ranged from 7.8 to 39 ppm (Agarwal, 1965). Prasad et al. (1967) reported that the content of total K varies with the presence of K bearing minerals like feldspar, micas and illite. The total availability of K is dependent on the extent of weathering of minerals (Chahal et al., 1976). Though it gives an idea of the content of soil potassium, yet all of it is not readily available to plants. It constitutes 97 to 98 per cent of the total soil K (Attoe and Trough, 1945). The soil potassium excluding soluble and exchangeable forms from that extracted with 1N HNO 3 represents non-exchangeable potassium. It is distinct from mineral K in that it is not bounded covalently within the crystal structure of soil mineral particles. It is held between adjacent tetrahedral layers of dioctahedral and trioctahedral micas, vermiculites and intergrades clay minerals (Rich, 1972). The Non-exchangeable K ions are strongly held by the negatively charged interlayer surface sites (Kittrick, 1966). Non-exchangeable potassium is the potassium trapped between negatively charged inter layer sites. Release of potassium from non-exchangeable pool is a rate limiting factor (Martin and Sparks, 1983).

12 Ram and Singh (1975) studied on different forms of K in twenty surface samples of cultivated paddy fields of eastern Uttar Pradesh and reported that available, fixed and HCl soluble K varied from 6.5 to 39.5, 64.0 to258.5 and to mg 100 g- 1 soil respectively. Available K was positively and significantly correlated with ph, Exch.Ca 2+, CaCO 3 and clay content of the soils. Fixed K also gave a significant positive correlation with clay content, ph and available K. HCl soluble K showed a significant positive correlation with fixed and non significant correlation with exchangeable K. Godse and Gopalkrishnappa (1976) studied the different forms of K in some black and red soils occurring in watershed areas of Tungabhadra river in Bellary, Karnataka and reported that the exchangeable, fixed,water soluble and HCl soluble K content of soil series under vertisols are generally higher than alfisol and related soils. Kalbande and Swamynatha (1976) observed that the variations in K content and its distribution in the soil profiles of black soils in Tungabhadra catchments were related not much to the differences in K content of the parent materials but more to the conditions of weathering. The potassium status of Tamil Nadu soils as reviewed by Krishnamoorthy et al. (1976) has revealed that in general the soils of the state appeared to be fairly supplied with potassium. The per cent total K 2 O and available K 2 O contents in red, black, alluvial and laterite soils were 0.81 and 0.163, 0.92 and 0.162, 1.14 and 0.105, 1.13 and and 0.92 and respectively. Ranganathan (1977) observed that the amount of water soluble fraction of K in the major soil groups followed the order alluvial>black>red>laterite in soils of Tamil Nadu. Water soluble form of soil K is highly mobile, which is not sufficient to meet the normal K requirements of the crops. This form is taken up directly by plants and microbes and is also subjected for leaching (Sparks, 1980) and this fraction is usually found in low quantities. The investigation on potassium status of soils of Karnataka by Ranganathan and Sathyanarayana (1980) revealed that the variations in K status of red, black, laterite and alluvial soils were due to minerals present, particle size and degree of weathering. They found that on an average the water soluble K constituted 0.23 per cent of total K and its higher value in surface soils was partly attributed to the upward translocation due to capillary rise. Exchangeable K constituted 2 per cent of total K and its vertical distribution seemed to be dependent on soil texture. Its content in soils studied was in the decreasing order; black<red<alluvial<laterite soils. The exchangeable K showed a positive and significant relationship with clay content. The fixed K constituted 6.6 per cent of total K and ranged from 250 to 660 ppm. The lattice constituted on an average 91 per cent of total K. Both the total and lattice K had positive and significant correlation with sand content and negative with clay revealing the presence of the unweathered K bearing minerals. There was a decreasing trend in exchangeable K with continuous cropping and the decrease was found to be more pronounced during the first crop than later crops in succession started removing K from non-exchangeable fractions after a substantial part of exchangeable K was exhausted (Patiram and Prasad, 1983 and Chakravarthi and Patnaik, 1990). Subba Rao and Sekhon (1987) reported that the potassium status of five soil series from eastern India which were under intensive rice-rice and rice-wheat cropping systems. They found that in soil of Hangram series high available K was associated with comparatively low reserve form. These soils dominated by smectite maintained a higher available K than those of Balishi (Orissa) amd Kharbona (West Bengal) once which were predominantly kaolinitic. Lattice K constitute about per cent of soil K in vertisols and associated soils (Sharma and Dubey, 1988). The positive correlation between lattice K and clay was evident because, this form of K is an integral part of clay. Subba Rao and Sekhon (1990) observed during investigation on distribution of potassium in nineteen well defined soil series of India and reported that in swell shrink soils both available and reserve K content was decreased with depth.

13 Adhikari and Ghosh (1991) reported that fine textured soils with relatively higher organic matter content had the highest water soluble K compared to coarse textured soils with low organic matter content. Higher water soluble K contents were present in saline sodic soils of Punjab (Dhillon et al., 1985). Similar results were also reported by (Pradeep Kumar et al., 1995). Bhake et al. (1992) made an extensive study on distribution pattern of different forms of soil potassium in the extensively rice growing areas viz., Chandrapur, Umared and Dapoli districts of Maharashtra state and reported that water soluble K ranged from 0.24 to mg K 2 O 100 g -1 of soil in Umared soils, while, Dapoli soil contained slightly more water soluble (0.42 to 1.25 mg K 2 O 100 g -1 soil). All the other forms of K however, were higher in Chandrapur and Umared soils than Dapolic soils, the exchangeable K ranging from to mg K 2 O 100 g -1 soil in the latter. The exchangeable K was the predominant sources of available K in all the soils and available K of Dapoli was significantly and positively correlated with total K, lattice K and exchangeable K, while in Chandrapur soils it was significantly and positively correlated with exchangeable K only. In Umared soils, available K was significantly and positively correlated with Total K and exchangeable K. The study on forms of potassium in some benchmark soils of India by Dhillon and Dhillon (1994) has revealed that 1N HNO 3 extractable K was highest in illitic alluvial soils followed by black and red soil. This form was significantly correlated with organic carbon and silt content of soils. Total K content was highest in red soil followed by alluvial soil and black soil, it was related to CaCO 3, CEC, sand and clay. Venkatesh and Sathyanarayana (1994) observed that the exchangeable K was positively correlated with clay, ph and CEC but negatively with sand and silt content and a significant positive correlation between total K with sand, silt and clay in some vertisols of North Karnataka. Total K was significantly correlated with clay in normal soils of Uttar Pradesh (Singh and Agarwal, 1995). The investigations on forms of potassium in rice growing areas representing three major soil orders of Bihar revealed that the higher water soluble and exchangeable K in vertisols was mainly due to high clay and organic matter content, which provide more surface area for exchange site. Total K showed a significant positive correlation with silt and clay indicating that substantial quantities of K bearing minerals were present in silt and clay fractions of all these soils (Prasad, 1995). A survey on available potassium status of major soils of Karnataka by (Shivaprasad et al., (1995) has shown that black soils have high, red soils medium and laterite soils low in respect of available K. The parent material and rainfall of the area found to be important factors governing the amount of available K. The K fertility declines over years under intensive cropping. The total and non-exchangeable K were positively correlated with per cent silt and clay and negatively with sand indicating that the finer particles contained higher amounts of potassium as compared to coarse fraction (Ghosh and Mukhopadhyay, 1997). Hebsur (1997) studied the potassium dynamics in black soils of North Karnataka under sugarcane based cropping system and reported that the range in contents of various forms of K in the soil profiles studied was to 0.62 mel -1 of water soluble K, 150 to 1250 ppm of non exchangeable K, 0.47 to 3.24 per cent of total K. The water soluble, non exchangeable and lattice constituted 0.02 to 0.206, 0.64 to 4.0, 0.87 to and 86 to per cent of total K, respectively. Raskar and Pharande (1997) observed that higher exchangeable K in surface layer than that of subsurface layers due to higher crop residue yielding higher humus content, K fertilizer application than in the subsurface layer and variation in clay content. They also reported that all forms of K in vertisols were positively and significantly correlated with each other. The ph, EC, CaCO 3 and organic carbon content in vertisol showed positively correlation with all forms of K.

14 Kuldeep Singh et al. (2001) reported that exchangeable, non-exchangeable, lattice and total K fractions were significantly correlated with clay indicating is being the reservoir of K. Lattice K showed poor relationship with exchangeable K. This would imply the poor replenishment of exchangeable K from lattice K. Dinagaran et al. (2006) studied on the K status of some representative soils of Haryana in relation to soil properties and reported that water soluble K was not significantly correlated with all other soil properties. The exchangeable K and non exchangeable K found to have significantly positive correlation with clay, silt, EC and CaCO 3 content and negatively with sand suggesting that available K status of the soils are largely governed by finer fraction of soil. Gupta et al. (2006) reported that all the Q/I parameter decreased with the increase in soil depth suggesting that the available of K is more in surface soil as compared to in the subsurface layer in some benchmark soils under rice wheat cropping systems in Punjab. 2.2 Dynamic equilibrium among different forms of soil potassium A dynamic equilibrium exists between solution K, exchangeable K, non-exchangeable K and mineral or lattice K. The various forms of potassium are interrelated and comprise a system in which an increase in one form occurs at the expense of one or more of the other forms (Sparks, 1980). K a = Adsorption rate co-efficient K d = Desorption rate co-efficient K 1 = Fixation rate co-efficient K 2 = Release rate co-efficient K 3 = Crystallization rate co-efficient K 4 = Weathering and dissolution Chatterjee and Rathore (1976) opined that the speed with which the equilibrium is established depends on factors such as expansion and contraction caused by wetting and drying, freezing and thawing cycles, the nature of mineral lattice eg: surface charge density, location of the charges and extent of the surface, the nature of the counter ions in the solution, the thickness of water films on adsorbing surface and the concentration of potassium ions relative to other cations in the equilibrium solution. Similar reports on dynamic equilibrium among forms of K were also expressed by several research workers (Ramanathan, 1978; Goulding, 1987; Tewatia et.al., 1989 and Sirajul Islam et al., 1994). The availability of K to the plants depended on dynamic equilibrium existing among the non-exchangeable, exchangeable and water soluble forms of potassium (Sharma, 1976). The soil with higher amounts of reserve K had higher amount of exchangeable K (Choudhari and Pareek, 1976). Sharpley (1989) observed a close relationship between water soluble K and exchangeable K and in turn released it to 1N HNO 3 extractable K and concluded that exchangeable and HNO 3 extractable K give better indication of the potential K supplying power of a soil and also the initial K pool sizes. Further reported that non-exchangeable K could give better indication of the potential buffering capacity of a soil, which helps in determining initial K pool size from the readily available K pool. Soil texture had a great influence on available and reverse K (non-exchangeable K) in soil series of eastern India (Subba Rao and Sekhon, 1987). Also, Talukdhar and Khera (1991) reported that subsoil contributed substantial amount of K from its non-exchangeable K pool towards crop uptake.

15 Sudharmai Devi et al. (1990) reported that a positive significant correlation between available K and fixed K, which was attributed to the dynamic equilibrium existing between the water soluble, exchangeable and fixed form of potassium. All the forms of soil potassium were inter-correlated, indicating the existence of dynamic equilibrium among them (Venkatesh and Sathyanarayana, 1994 and Ghosh and Mukhopadhyay, 1996). Patil and Sonar (1993) studied on different fractions of K in swell and shrink soils of Maharashtra and reported that the correlation between different fraction revealed that exchangeable K was significantly correlated with non exchangeable K, lattice K and total K. Similar correlation between non exchangeable K with lattice and total K and lattice with total K indicating equilibrium between different forms of K were noticed. Mishra et al. (1995) reported a significant positive correlation between total K and lattice K while, negative with exchangeable K in some mica rich soils of Bihar. Singh et al. (2001) reported that the contribution of exchangeable and nonexchangeable K was found to be almost similar towards meeting K requirements of most the crops. The release of non-exchangeable K was non significantly correlated with a number of physico chemical properties namely ph, EC, OC, CaCO 3, sand silt and clay but was positively correlated with cumulative dry matter yield (r = 0.591**) and cumulative K uptake (r = 0.784**). Byju et al., (2000) Indicated that the soil K maintained a dynamic equilibrium among its various forms due to the effect of different K levels on K fractions in black soil. The levels of solution K were affected by the equilibrium and kinetic reactions that occur between the forms of soil K, the soil moisture content and the concentration of bivalent cations in solution and on the exchangeable phases (Sparks, 2002). 2.3 Potassium reserves in different size fractions of soil Potassium bearing primary minerals dominates the coarse sand and fine sand whereas, the potassium bearing minerals are present in the silt and clay. The contribution of different size fractions of soil to total potassium content of soil depends upon the K content of each fraction and its proportion in the soil. Ranganathan and Sathyanarayana (1980) observed that among the sand fractions red soils had more K followed by alluvial, laterite and black soil indicating presence of less weathered K bearing minerals in red soil. The K content in silt fraction followed the order of red>alluvial>black> laterite soil, while in clay it was highest in alluvial followed by red, laterite and black soils. In black soil, the majority of K to total K content was from clay fraction. Adhikari and Ghosh (1991) observed that the total K content of the different size fractions increased with decrease in particle size. The lower content of K in sand was due to dilution effect by quartz which increased with particle size. Sharma and Sekhon (1993) reported that the total K in different size fractions of three black soils and two red soils varied from 0.6 to 5.33 per cent. The per cent contribution of sand to total K was highest in red soils followed by black soil. The contribution of silt and clay was more in fine texture soils. Contribution of textural fractions namely coarse sand, fine sand, silt and clay towards the total soil potassium varied from 0.37 to 9.52, 0.52 to 19.16, 5.87 to and to per cent. The higher K contribution from clay fraction towards total soil K might be due to high clay content and presence of potassium bearing minerals in the finer fractions (Venkatesh and Sathyanarayana, 1994). 2.4 Potassium releasing power of soils Potassium releasing power of the soil refers to the inherent capacity of the soil to supply potassium to growing plant from its natural source. As the quantity of exchangeable K in the immediate vicinity of the feeding tip of roots diminished, the replenishment in this area takes place by release of potassium from non-exchangeable K form. Nash (1971) reported that the chemically extractable potassium that may be present in the soil would not provide adequate meaningful information unless the rate of its release as well as the concentration in the soil solution is included for actual assessment of the supply of K to the plants.

16 Although the potassium releasing and supplying power of soil are often used as synonyms, the two terms have distinct implications In an empirical approach on the rate of release of non-exchangeable K with continuous acid extraction in order to know the long term K supplying power of soils, Haylock (1956) referred constant rate, where as step K as highly soluble K mostly released in the initial stages, when K is extracted with 1 N HNO 3. Further used step K values in classifying soils as follows. Step K values<12 mg 100g -1 deficiency is expected; Step K values between 12 and 19 mg 100 g -1 soil response to added K is likely when removal of K is intense; Step K values>19 mg 100g -1 soil no response to added potassium is expected. The CR-K and step K varied from to and from to cmol (p + ) kg -1, respectively in soils of Nagarjunasagar left bank canal area by Chandrashekar Rao and Prasad Rao (1981). Step K was more in the unfertilized plots than in the intensively fertilized plots with N and P as noticed by Patra and Khera (1982). Patiram and Prasad (1983) observed that the release of non-exchangeable K has been used to evaluate the long term K supplying power of soil. Wheat crop utilized about 86 per cent of the total K uptake from non exchangeable sources (Krishna Kumari et al., 1984). But this contribution was negligible when K fertilizer was applied. At higher levels of K application, there was a build up in the non exchangeable K. When no K was applied, the crop utilized about 95 per cent of the K from non exchangeable sources and it decreased to 59 per cent at 53.5 mg kg -1 soil and 13 and 22 per cent at 107 and mg kg -1 levels respectively. Subba Rao et al. (1984) reported that, the cumulative release of K values indicated that the alluvial and black soils had greater K supplying power than red laterite and sandy soils. Sharpley (1989) reported that the capacity to supply K under continuous cropping was greater for smectitic than kaolinitic soils of similar exchangeable K contents and hence determination of both exchangeable and HNO 3 extractable K could give a better indication of the potential K supplying power of the soil. Release of non-exchangeable K was more from alluvial and red soils than from lateritic and black soils (Chakravarthi and Patnaik, 1990). Maji and Chatterjee (1990) observed that the available K from non-exchangeable sources was higher from smectite dominant black soils as compared to that from illitic red soils. Boruah et.al. (1990) reported that fine textured soils of Assam similar trend was observed for K release at each step of successive extraction. Further, the step K values had a significant positive relationship with exchangeable and non-exchangeable K contents of Entisols and Inceptoisols. Deshmukh and Khera (1992) observed that the step K was significantly correlated with clay content, silt content, total K and CEC in eight alluvial soils of Delhi. Further, they indicated that the step K procedure was reliable for the prediction of plant utilizable K from these soils. Krishna kumari and Khera (1992) reported that 70 per cent of the total step K was released from an Inceptisol under intensive cropping in the first two extractions with boiling 1N HNO 3. Pal and Mukhopadhyay (1992) reported that a positive correlation between cumulative K release and initial level of exchangeable and non-exchangeable K, which indicated that it was the K status which governed the K release characteristics of soils Talukdar and Das (1994) reported that step K values of more than 1.5 c mol (p + ) kg -1 in soils of the orders, Inceptisols and Entisols, which indicated that all the soils had high K reserves that exceeded response level. Further, they stated that entisols and inceptisols were K deficient, while, alfisols were K sufficient, when critical CR-K values of < 0.2 cmol (p + ) kg -1 was considered for differentiation. It was also observed that Alfisoils had higher CR-K than inceptisols or entisols. CR-K values remained unaltered even after cropping irrespective of the level of K application in six typical soils belonging to inceptisols, vertisols and alfisols (Hariprakash Rao and Subramanian, 1995). Mehta et al. (1995) observed that, the non-exchangeable K, in entisols was released in two steps, an initial rapid release from edge sites followed by slow release from interlayer sites with in the clay mineral.

17 Das et al. (1997) observed that the potassium release parameter like total extractable K, total step K and CR-K varied widely in different locations (watershed areas) of Phulbani district, Orissa indicating a wide variation in the K supplying capacity of these soils. Total extractable K and total step K were positively correlated with each other. Both the K release parameters were also positively correlated with non-exchangeable K, lattice K and total K indicating that non-exchangeable K may serve as a good index of the K supplying capacity of these soils (Pal et al., 2001). Arabindadhar and Sarojkumar Sanyal (2000) observed that the cumulative release of non-exchangeable K by repeated extraction with boiling 1N HNO 3 followed a semi logarithmic behavior with increasing number of extractions, suggesting that the release of nonexchangeable K decreased with successive number of extractions. The reserves of step K content were in general related to the content of the clay fractions of the soils. Hirekurabur and Satyanarayana (2001) reported that the K release characteristics such a cumulative K release was positively and significantly correlated with clay (r = 0.520*) and non-exchangeable K (r = 0.634**); step K was significantly and positively correlated with clay (r=0.432*) and non-exchangeable K (r = 0.807**); constant rate K was positively and significantly correlated with clay (r = 0.593**) and non-exchangeable K (r = 0.900) which indicated that the clay fraction and non-exchangeable K served as good index of K supplying capacity of the soils. Pasricha and Bansal (2002) reported that cumulative K release from some of the benchmark soil series of India and found that the soils dominant in kaolinite mineral released K at slower rate as compared to the illite soil. The continuous and adequate K nutrition of plants depends not only on the amount of plant available K in soils but also on its rate of release to the soil solution. Vertisols and associated soils with relatively low level of this ratio have available K but low to medium non-exchangeable K which under long term cropping may depleted faster. In soils with low levels of both exchangeable and non exchangeable K, potassium application must be done to realize the yield potential of crops (Srinivas Rao et al., 2010). 2.5 Potassium fixation capacity of soils Potassium fixation refers to the conversion of added or unused K into a form, which, is temporarily unavailable or difficultly available. Potassium fixation by soils and clay minerals has been studied extensively because its importance in understanding the dynamics of K in agricultural soils. One of the major problems, that limit the efficiency of potassium fertilizers applied to the soil is its fixation by various minerals present in soils. But, it is not a total loss, as the fixation of K retard the loss of K by leaching and excessive uptake by plants. The suggested mechanism of K fixation is by emplacement of K, between basal K surfaces, where it fits into the hexagonal cavities formed by tetrahedral oxygen of 2:1 type of clay minerals (Shaviv et al., 1985). Diffraction studies indicated that fixation of potassium was accompanied by collapse of 14 A o reflection to 10 A o (Sidhu and Gilkes, 1977; Sidhu and Dhillon, 1985). Generally the fixation of applied potassium was highest in micaceous soils containing high amounts of clay (Dhillon et al., 1989). Soils dominated by montmorillonite fix much higher quantities of potassium as compared to kaolinite dominant soils (Ng Siew Kee, 1966). The extent of K fixation in representative soils of South India ranged from 4 36 per cent of the added K and the magnitude of K fixation by soil was in the order of alluvial > black > red > laterite (Ramanathan and Krishnamoorthy, 1978 and Barbar, 1979). They also reported that K fixation was very much dependent on finer fractions (clay and silt) of the soil irrespective of their individual characteristics as they provide more surface area and increased number of fixation sites. Ranganathan and Satyanarayana (1980) reported the fixation of potassium in different soils of Karnataka and found that the fixation was more in subsurface layer (15 30cm) of red, black and laterite soils and increased with depth in alluvial soils. The K fixing capacity of the soils was in the following order: black > alluvial > red > laterite soils.

18 The higher K fixation in black and alluvial soils was attributed to the dominance of montmorillonite and illite, respectively and low fixation in red and laterite soils was because of kaolinite. Bajwa (1981) reported that the fixation of K by beidellite and vermiculite clays was found to be reduced by the simultaneous occurrence of other mineral species. He also noticed that the influence of mineralogical variations in the soil clays on K fixation under the moist temperature regimes usually prevalent in tropical upland rice soils, Beidellite clay was the most severe fixer of added K (80%) followed by vermiculite (69%) clays. Fixation was not appreciable (<15%) in clays consisting of montimorillonite, amorphous materials, chlorites, hydrous mica, kaolinite and halloyusite. Singh et al., (1984) reported that the soils having higher K fixation capacity had exchangeable Ca varying from 77 to 92 per cent of the exchange complex. The potassium fixing capacity of soils of Agra regions, Uttar Pradesh, varied from 8.8 to 35.5 mg 100 g -1 soil with a mean value of 21.3 mg 100 g -1 and the fixation was positively and significantly correlated with cation exchange capacity and clay content (Chandraprakash and Vinay Singh, 1985). Aravind and Muthuswamy (1989) from their study on K fixation under intensive cropping and fertilizer use concluded that continuous addition of fertilizer nitrogen alone or in combination with phosphorus to a vertisol subjected to intensive cropping for a number of years caused depletion of soil K resulting in increased fixation of the applied potash. Exhaustive rice cropping increased the K fixing capacity for almost all the rice growing soils studied (Chakravarthi and Patnaik, 1990). The K fixation capacity in surface and subsurface soil was complex in a long term field experiment on clay loam soil. There was an enhanced rate of K fixation in the treatments that has not received any K for the past 15 years. The K fixation was significantly higher in subsurface than in surface layer (Aravind and Muthuswamy, 1989). Boruah et.al. (1991) observed that the amount of K fixed in the soil was in the order of alfisol > entisol > inceptisol. The fixation increased with increasing rates of K application. But, per cent of added K that was fixed decreased gradually. The amount of K fixed showed positive relationship with clay and silt fractions of soils, irrespective of soil orders. Except with Entisols, ph was correlated significantly with amount of K fixed while, in other soils K fixation correlated significantly with CEC of soils. Alluvial soils in general had high K fixation capacity as against laterite soils of Assam and the reason for high K fixation for alluvial soils was attributed to the presence of mica and vermiculite (Basumatary and Bardolui, 1992). Sannigrahi (1994) reported that the soils of Nizamsagar catchments had the potassium fixation capacity in the order: entisols > vertisols > inceptisols. The potassium fixing capacity of soils of Uttar Pradesh varied widely in different soils depending upon the relative abundance and mineralogical makeup of the clay fraction (Tiwari and Vandana Nigam, 1995). Hebsur (1997) reported that the potassium fixation of surface soils under sugarcane based cropping system of north Karnataka ranged from, 0.39 to 1.32 c mol (p + ) kg -1. The highest fixation was observed in black soil from Gangavathi, which could be due to the dominance of chlorite in clay fractions. Mixed black and red soils had higher K fixing capacity due to the presence of vermiculite. He also observed a significant positive relationship between K fixation and clay content but non-significant correlations of K fixation with ph, CEC, fine sand and exchangeable Ca plus Mg was also observed. Amiri and Dordoi (1997) reported, the potassium fixing capacity ranged from 4 50 per cent with a mean value of 37.3 per cent. K fixation capacity was higher in Safroud and Shalmanroud soil series of Iran. This would indicate that those soils contained mica or illite in addition to an abundance of smectite group minerals. Srinivasa Rao et al. (2000) observed that fixation of added K increased with the rate of added K in all cases of soil mineralogy and depth. Surface soils of vertisols and vertic subgroups showed greater K fixation (26 32%) followed by illitic inceptisols, alfisols and aridisols (23-29%) whereas, lower fixation values were found for kaolinitic alfisols and inceptisols (17-23%).

19 The overlapping among the soils belonging to different mineralogical groups as regard to the extent of K fixation was ascribed to the composition of the associated minerals in silt and clay fractions of soils. 2.6 Response of crops to potassium application Singh and Brar (1977) observed that as high as 80 per cent of available K is being contributed by non-exchangeable form of potassium and this high contribution from nonexchangeable pool could be one of the possible reasons for poor correlation of exchangeable K to plant response. Similar results were also obtained by Singh et.al., (1983). Pillai et al. (1987) summarized the response of crops to K in selected cropping systems in long term experiments in different regions of India. Rice responded to K in rice-rice and rice-wheat cropping systems. The uptake of K by the crops even at optimal level of NPK was far in excess of fertilizer K applied, indicating inadequate K application and much grater exploitation of native K reserve of soil. Nambiar and Abrol (1989) studied intensive cropping systems at different locations in India and reported positive response to K application at many locations in maize, rice and wheat. Rice-rice system responded to K application in both kharif and rabi season at Bubaneswar. The nutrient removal in rice-rice cropping system depends on production level, soil type and whether crop residues are removed or recycled in the soil. Optimum application of N increased the K uptake by 57 per cent over control and N and P application increased the K uptake by 145 per cent (Tandon and Sekhon, 1988). Tandon (1990) computed the per cent contribution of N, P, K and FYM to total response in different cropping systems in long term experiments and reported that potassium contributed very considerably to yield in rice-rice and maize-wheat cropping sequence at Bubansewar and soybean- wheat at Ranchi. Sekhon and Biswas (1992) reported that in a long term experiments with rice and wheat system at Ludhiana, it was rice which responded more to K application rather than wheat. Yadav et al., (1993) reported that application of 20 to 30 kg K 2 O ha -1 in pulses like gram, lentil and pigeon pea under rainfed conditions had a positive response in cultivators fields in alluvial soil. They also observed that application of 40 to 60 kg K 2 O ha -1 to oilseeds had positive responses to the application and increased the yield by 1.5 to 3.5 kg grain kg -1 K 2 O under rainfed conditions in cultivator s fields in alluvial soil. Singh and Prasad (1996) studied the direct and residual effect of P and K in ricebengalgram cropping system in a sandy loam soil and reported that application of P and K in both the seasons (kharif and rabi) increased the rice equivalent yield of the system significantly. Additions of high doses of P and K increased grain yield of the system by 10.5 and 4.9 per cent, respectively and also resulted in increased availability of these nutrients in the soil. Prasad and Prasad (1997) studied the response of rice to K application in calcareous soils series. The highest grain yield of rice was recorded with 90 kg K 2 O ha -1 application. Depending soil test value response of rice to K application ranged from 5.5 to 28.3, 2.1 to 20.0 and 0.6 to 16.7 kg grain kg -1 K 2 O in soils containing low, medium and high available K, respectively. Singh and Jagadeesh Prasad (1997) studied on the relative response of chickpea to potash fertilization and reported that potassium application significantly increased dry matter production and grain yield. Tiwari (1999) studied the response of sunflower, safflower, linseed, pea, lentil and chickpea in alluvial soils of Uttar Pradesh and reported that application of 50 kg ha -1 of K to all the crops increased the grain yields. In sunflower 1674 kg ha -1 and in chickpea 2945 kg ha -1 was recorded compared to control (1463 and 2406 kg ha -1 )

20 Surekha and Narayana Reddy (2000) from their study reported that the moderate supply of K (40kg K 2 O ha -1 ) along with N and P fertilizers ensured higher grain yield of both hybrids and high yielding varieties of rice, with a higher magnitude of increase in case of the hybrids. The depletion of soil available K in treatment receiving only N and P indicated the need for balanced application of NPK fertilizers under intensive rice cropping. Tomar et al., (2002) studied the response of chickpea to potassium in calcareous soils and reported that potassium application had significant influence on the concentration of K and N of grain and straw and P of straw. Potassium content in grain and straw increased with the application of K and it was on par at 50, 75 and 100 kg K 2 O ha -1 Yaduvanshi and Anand Swarup (2006) application of N alone enhanced K concentration in straw in a long term experiment on rice-wheat cropping system. Application of NPK fertilizer and manuring significantly influenced the availability and release of soil K. Both exchangeable and non exchangeable K decreased in the treatments without K. Growing sunflower and chickpea without manure and reduced or imbalanced fertilization resulted in lower yields and lower gross and net returns in both the crops in a sunflower- Bengal gram sequence (Anon., 2003). Srinivasa Rao et al., (2003) summarized the results of 498 experiments on cultivator s field on chick pea, urd bean, lentil, pigeon pea and mung bean under rainfed conditions. The results indicated that all the crops responded to K application at 20, 30 and 40 kg K 2 O ha -1 levels. The responses and additional profits were higher with 20 kg K 2 O ha -1 followed by 30 and 40 kg K 2 O ha -1 over constant doses of N and P. Subba Rao et al. (2003) reported that in wheat- sorghum system on an alluvial soil the exchangeable K decreased in subsoil of plots receiving no K than those of recommended dose of K. Shrotiya (2005) conducted large scale demonstrations on balanced fertilization in chickpea, paddy and groundnut and reported that in all the demonstrations the yields in balanced fertilization plots (NPK) were higher than farmers practice. The yields of sunflower and chickpea increased with balanced application of NPK fertilizers. The yields recorded were 2041 kg ha -1 in sunflower and 2079 kg ha -1 in chickpea compared to N and NP application in long term fertilizer experiment on sunflower-chickpea cropping sequence at both Raichur and Nandyal centres (Anon., 2006). Channabasavanna et al., (2008) reported that application of 100 per cent RDF to maize in kharif and 50 percent RDF to chickpea in rabi recorded significantly higher seed yield. (1152 kg ha -1 in maize and 992 kg ha -1 in chickpea) indicating the residual effect of fertilizer applied to maize in maize-chickpea cropping sequence. Muthukumararaja et al. (2009) revealed that addition 50 kg K 2 O ha -1 recorded higher grain (5263 kg ha -1 ) and straw (5621 kg ha -1 ) yield in rice in both kharif and rabi seasons respectively in rice-rice cropping sequence Uptake by crops Ganeshmurthy and Biswas, (1985) reported that a positive correlation between K removal by crops and non-exchangeable K released from the soil. Richards and Bates (1988) observed that a close relationship between total K uptake and the uptake of nonexchangeable K by crops under exhaustive cropping studies. Tandon and Sekhon, (1988) reported that total uptake of K 2 O in rice was 30 kg, sunflower 105 kg and chick pea 49.6 kg per tonne of produce. In rice rice cropping systems it removes on an average 211 kg of K 2 O ha -1 per year where as soybean- wheat cropping system removes 204 kg ha -1 per year. Rice crop removes on an average 15 kg N, 4 kg P 2 O 5 and 24 kg K 2 O in the ratio of 1:.0.23:1.6 to produce one tonne grain with an equal amount of straw from soil (Anon., 1992). Talukdar and Khera (1991) reported that more than half of the total exchangeable K requirement of crops was contributed from subsurface layers. Relative contribution of exchangeable K and non exchangeable K decreased with depth.

21 If only surface layer is taken into account, the contribution from non exchangeable K towards total K uptake by crops was more. They also showed that if whole profile contribution is taken into consideration, the proportion of non-exchangeable K decreased and that of exchangeable K increased. The concentration and uptake of K in rice increased with increasing available K status of the soil, the values being highest in the soils testing high in exch-k and Non exch-k. Added K also resulted in enhanced K concentration and uptake in different plant components compared to control. The response was more in soils testing medium to low in available K (Ashok Tiwari and Mishra, 1995). Devendra Singh et al. (1999) reported that the uptake of K by grain and straw of rice significantly increased with increase in K application. It was highest in 180 kg ha -1 level (29.8 and kg ha -1 ) and lowest in control (14.5 and 74.6 kg ha -1 ). The highest removal of K from soil, may be due to higher production of grain and straw. However, at 90 kg K 2 O ha -1 and above, the percentage increase in uptake was not very much pronounced. Khera et al. (1999) reported that paddy removes an average of 30.0 kg, chick pea 49.6 kg and sunflower 105 kg of K 2 O per tonne of produce. Pasricha (1999) revealed that in rice-wheat cropping system, a total yield of 10 tones of rice and wheat removes almost 300 kg K 2 O ha -1 /year. Potassium content in grain increased with the application of K, along with N at 25, 50 and 75 kg K 2 O ha -1 was found to be at par and same was observed in straw. The increase in K content could be attributed to increased availability of applied K near the root zone. The increase in K and N content in grain and straw might complementary uptake effect between N and K (Tomar et al., 2002). Ravichandran and Sriramachandrashekharan (2011) reported that under balanced nutrition and optimal growth condition rice removes an average of 17 kg K per tonne of economic yield under irrigated condition. However, in the farmer s field, K use efficiency was 60 kg grain per kg of K taken up. 2.8 Minerology of clay fraction in relation to potassium bearing minerals Majority of the total potassium in soil was in the minerals such as feldspar, muscovites and biotites (Sparks, 1987; Sparks and Haung, 1985 and Wilson, 1992) and it is contained in the sand fraction of the soil (Sparks, 1987; Sandusky et al., 1987 and Robert, 1992). Among the clay minerals, illite has substantial amount of potassium. The relative availability of K from K bearing minerals was in the order biotitic > muscovite > orthoclase > microcline. The release of K from potassium silicate minerals occurring in soils decreased markedly with time (Rich, 1968). The potassium in soil owes its origin to the primary rock minerals, the K-feldspar and the K-micas, which undergo weathering on the surface of the earth. Potassium is present in soils as a structural constituent of the feldspars and micas, as a exchangeable ion associated with the soil colloids and as potassium in soil solution. Plant uptake of K is related to the last two which, however, were derived from the potassium bearing mineral by weathering (Sharma, 1976). Among the clay minerals present in soils, the micas, vermiculites, illites, weathered micas and smectites had the property of exchanging K ions (Chatterjee and Rathore, 1976). Sidhu, (1983) observed, about 65 per cent of the total K in the form of micas (muscovite, biotite and illite), the remaining K in feldspars (microcline and orthoclase) in three alfisols developed on alluvium in West Bengal. The feldspar K content in clay was the lowest when compared to sand and silt fractions and reverse trend was noticed with respect to mica in these soils. Sahu et al. (1983) noticed a higher proportion of potash feldspar and mica in two red soils of Orissa which were responsible for the dominance of illite in clay fraction. Sometimes, red soils occur in association with laterite soils. The clay fraction of red soil was not exclusively kaolinitic and contained illite and montmorillonite when pedogenic process of high temperature and extensive leaching operated over long periods on geologically old parent materials. There was rapid and fairly complete alteration of weatherable minerals into secondary clays and oxides (Agarwal and Bali, 1984).

22 Mineralogical studies on alluvial, red and lateritic soils of Burdwan district of West Bengal by Ghosh and Ghosh (1984) indicated that the clay fraction of laterite and red soils was dominantly kaolinite and that of alluvial soil contained mica and smectite in almost equal proportion. Fairly high amount of smectite and interstratified minerals in laterite soil and 23 per cent vermiculite on the transitional red soils were the other noteworthy features of these clays. No feldspar mineral was detected and only illite was the most abundant mineral in the clay fractions of three benchmark soils of Punjab (Sidhu and Dhillon, 1985). Tewatia et al. (1989) reported that clays of some salt affected soils of Haryana were dominantly illitic, associated with kaolinite, mixed layer minerals, smectite and chlorites. Potassium in micaceous form dominated over feldspathic form in soils of five soil series of eastern India and clay fractions of all the series were richer in mica-k (Sharma et al., 1992). Pal and Durge (1993) attributed the differences in the release of K from clay fraction of six alluvial soils to clay mineralogy. The X-ray analysis indicated that semiarid clays (Haryana and Delhi), containing more biotite, released more K, whereas, per-humid clays (Assam) containing more muscovite released least potassium. Rao et al. (1993) reported that kaolinite dominated soils were low in K, smectite dominated soils medium and illite dominated soils were high to very high categories. Potassium reserves in some soils of southern India revealed that in general, mica K predominated in finer fractions and feldspar K in coarser fractions (Sharma and Sekhon, 1993). Dhillon and Dhillon (1994) while, studying potassium in some benchmark soils of India found that the dominant clay mineral in alluvial soil sample was illite, whereas, smectite (beidellite nature) was the most abundant clay mineral in sample of black soils, which also contained small amounts of micas. Most of the clay fractions in red samples consisted of kaolinite, micas and iron oxides (goethite and haematite). Rao et al. (1994) reported that the presence of large quantities of illite in clays was responsible for the K replenishment rates under intensive cropping in eight soil series (Ustochrepts) from Delhi. Pharande and Sonar (1997) studied the clay mineralogy of some vertisol soil series developed on basalt/basaltic alluvium under different agro- climatic regions of Maharashtra and observed that smectite was the most dominant phyllosilicate in fine clays (> 90%) with small proportions (< 10.0%) of kaolinite. Hebsur (1997) and Gali (1998) also observed the dominance of smectite in the clay fraction of black soils of North Karnataka irrespective of their parent material.

23 3. MATERIAL AND METHODS In order to achieve the objectives, investigations were carried out under both field and laboratory conditions. The details of the experiments and methodology adopted are given below. 3.1 Field Experiments Location The field experiments were conducted in the farmer s field at Kasbe camp in Raichur taluk on paddy- paddy cropping sequence under irrigated and sunflower bengal gram cropping sequence under rainfed condition at Gabbur village in Deodurga taluk of Raichur district during and The experiments were laid out in Randomised Bblock Design with three replications and seven treatments. The plan of layout of the experiment is given Fig Climate The data on climatic parameters such as rainfall, maximum and minimum temperatures and relative humidity recorded during the period of experimentation ( ) provided by the Agro-advisory Service Unit, Main Agricultural Research Station, Raichur, UAS, Raichur is presented in Table 1 and rainfall pattern for the above years is depicted in Fig Soils The soils of the experimental site belong to dominant soil series of Raichur vertisols (Typic haplusterts). The characteristics of the soils of paddy-paddy and sunflower-bengalgram sequences are presented in the Tables 4 and Crops Paddy-Paddy sequence (irrigated) Sunflower-Bengal gram sequence (rainfed) Treatment details The treatment details are given below. : Kharif - Paddy (Sona masuri) : Rabi - Paddy (Rasi) : Kharif - Sunflower (KBSH-1) : Rabi - Bengal gram (A-1) T 1 Absolute Control T 2 Farmer s practice T 3 Recommended N alone T 4 Recommended N and P T 5 Recommended N, P and 50% RD K T 6 Recommended N, P and 75% RD K T 7 Recommended N, P and 100% RD K (RDF) In the farmers practice, farmers are applying imbalanced application of fertilizers. The details of fertilizer application by the farmers are given below. To collect this information survey was conducted and information was collected in questionnaire. Paddy : % RD N, 100% RD P 2 O 5 and 25% RD K 2 O Sunflower : 50-75% of RD N and P 2 O 5 without K Bengal gram : 50-75% of RD N and P 2 O 5 without K (RD Recommended dose)

24 Table 1. Meteorological data of the Raichur district for the years and recorded at Agro-meteorological Services Unit, MARS, Raichur Month Rainfall (mm) Maximum Temperature ( o C) Minimum Relative Humidity (%) April May June July August September October November December January February March Total April May June July August September October November December January February March Total

25 300 RF (mm) Max. Min. RH (%) M o nths o f cro pping seaso n 350 RF (mm) Max. Min. RH (%) M o nths o f cro pping seaso n Fig. 1: Meterological data of the Raichur district for the year and recorded at Agro-meteorological Services Unit, MARS, Raichur

26 3.1.6 Fertilizer recommendation Paddy (Kharif) Paddy (Rabi) Sunflower (Kharif) Bengalgram (Rabi) : 100:75: 75 kg N, P 2 O 5, K 2 O/ha : 100:75: 75 kg N, P 2 O 5, K 2 O/ha : 60:75:60 kg N, P 2 O 5, K 2 O/ha : 25:50:0 kg N, P 2 O 5. K 2 O/ha A basal dose of 10 t/ha was applied uniformly on the surface and incorporated into soil every year Transplanting or sowing Twenty five days old seedlings of paddy were transplanted during first week of August for kharif and during III week of November for rabi crop. Sunflower seeds were dibbled during first week of August for kharif crop and bengalgram during first week of November for rabi crop during and The seed rate, spacing, cultural operations required and plant protection measures recommended for cultivation of paddy, sunflower and bengalgram were followed as per the package of practices Biometrical observations Paddy : Number of tillers, test weight, grain yield and straw yield. Sunflower : Bengalgram : Head diameter, test weight, grain yield, straw yield and oil content. Number of developed pods, test weight, grain and straw yield. 3.2 Laboratory Studies Collection of soil samples Surface and sub surface soil samples from different villages growing paddy-paddy sequence under irrigated and sunflower-bengalgram sequence under rainfed conditions representing dominant soil series of Raichur (medium to deep black soils) were collected. From each village, five soil samples were collected depth wise (0-15 and cm) for this study. The details of the soil samples collected from villages of paddy-paddy sequence are given in Table 2 and sunflower-bengalgram sequence in Table 3. The surface and subsurface soil samples from the experimental plots of paddy-paddy and sunflower-bengalgram sequence were also collected before the initiation of the field experiment and after the harvest of the crop for analysis of various soil characteristics Methods of analysis The soil samples collected from different villages representing paddy-paddy and sunflower-bengalgram cropping sequence and also the samples of experimental sites were analyzed for physico-chemical components and important other characteristics by employing the standard procedures. Sl. No. Parameter Methodology Reference 1. Particle size analysis International pipette method Piper (1966) 2 Soil reaction Soil water suspension (1:2.5) Jackson (1973) 3. Electrical conductivity Soil water extract (1:2.5) Jackson (1973) 4. Organic carbon Wet oxidation method (Walkley and Black) Jackson (1973) 5. Calcium Carbonate Rapid acid neutralization Piper (1966) 6. Cation exchange capacity Sodium saturation method Black (1965) 7 Plant analysis Wet digestion with di-acid mixture. Jackson (1973)

27 Fig 2. Plan of layot of fild Experiment

28 Table 2. Details of the soil samples collected from villages for study under paddy-paddy cropping sequence Sl. No. Name of the village Taluk District Soil type Geology Soil Classification Rainfed/ Irrigated 1. Kasbe camp Raichur Raichur Black Gneiss Typic haplustert Irrigated 2. Vijayanagar camp Raichur Raichur Black Gneiss Typic haplustert Irrigated 3. Kalmala Raichur Raichur Black Gneiss Typic hapluetert Irrigated 4. Ganjalli Raichur Raichur Mixed red and black Gneiss Typic pallustert Irrigated 5. Devasugur Raichur Raichur Mixed red and black Gneiss Typic palluetert Irrigated 6. Sirwar Manvi Raichur Black Gneiss Typic haplustert Irrigated 7. Harvi Manvi Raichur Black Gneiss Typic haplustert Irrigated 8. Neermanvi Manvi Raichur Black Gneiss Typic haplustert Irrigated 9. Amarewara camp Manvi Raichur Black Gneiss Typic haplustert Irrigated 10. Potnal Manvi Raichur Black Gneiss Typic haplustert Irrigated 11. Jawalgera Sindhanur Raichur Black Gneiss Typic haplustert Irrigated 12. Raithanagar camp Sindhanur Raichur Black Gneiss Typic haplustert Irrigated 13. Araginamara camp Sindhanur Raichur Black Gneiss Typic haplustert Irrigated 14. Gorebal camp Sindhanur Raichur Black Gneiss Typic haplustert Irrigated 15. Hanchinal camp Sindhanur Raichur Black Gneiss Typic haplustert Irrigated

29 Table 3. Details of the soil samples collected from villages for study under Sunflower-bengalgram cropping sequence Sl. No. Name of the village Taluk District Soil type Geology Soil Classification Rainfed/ Irrigated 1. Raichur Raichur Raichur Black Gneiss Typic haplustert Rainfed 2. Ashapur Raichur Raichur Black Gneiss Typic haplustert Rainfed 3. Hosur Raichur Raichur Black Gneiss Typic haplustert Rainfed 4. Nelahal Raichur Raichur Black Gneiss Typic haplustert Rainfed 5. Dinni Raichur Raichur Black Gneiss Typic haplustert Rainfed 6. Kallur Manvi Raichur Black Gneiss Typic haplustert Rainfed 7. Hokrani Manvi Raichur Black Gneiss Typic haplustert Rainfed 8. Kurdi Manvi Raichur Black Gneiss Typic haplustert Rainfed 9. Betadur Manvi Raichur Black Gneiss Typic haplustert Rainfed 10. Chikalparvi Manvi Raichur Black Gneiss Typic haplustert Rainfed 11. Gabbur Deodurga Raichur Black Gneiss Typic haplustert Rainfed 12. Kakargal Deodurga Raichur Black Gneiss Typic haplustert Rainfed 13. Maldakal Deodurga Raichur Mixed red and black Gneiss Typic haplustert Rainfed 14. Yermerus Deodurga Raichur Mixed red and black Gneiss Typic haplustert Rainfed 15. Mustur Deodurga Raichur Black Gneiss Typic haplustert Rainfed

30 3.3 Determination of various forms of soil potassium Water soluble potassium Water soluble potassium was determined in 1:2 soil water suspension after shaking them for two hours and allowing them to stand for an additional 16 hours (MacLean, 1961). The potassium in the extract was determined by flame photometer Exchangeable potassium The neutral normal ammonium acetate method as outlined by Knudsen et al. (1982) was followed Ten grams of sample was treated with 25 ml of neutral N NH 4 OAc. The suspension was shaken for ten minutes and then centrifuged until the supernatant liquid was clear. The solution was decanted into a 100 ml volumetric flask. Three more additional extractions were made in the same manner and the combined extract was diluted to volume of 100 ml with NH 4 OAc. The solution was mixed and K content was determined by using flame photometer Non exchangeable potassium Non exchangeable potassium was determined by boiling nitric acid extraction method as outlined by Knudsen et al. (1982). Two and half grams of finely ground soil were boiled gently with 25 ml of 1N HNO 3 for 10 minutes. The contents were filtered and filtrate was collected into a 100 ml volumetric flask. The soil was then washed four times with 15 ml portions of 0.1 N HNO 3. After diluting to volume and mixing, the potassium in the extract was determined using flame photometer. The quantity of K extract with the NH 4 OAc extract was subtracted to get the non exchangeable potassium content in the soil Total potassium The total potassium content was determined by digesting the soil samples with hydrofluoric acid in a closed vessel (Lim and Jackson, 1982). Finely ground 0.2 g soil sample was transferred into a 250 ml wide mouth polypropylene bottle. Two ml of aquaregia was added to disperse the sample. Later 10 ml of hydrofluoric acid was added by means of plastic pipette and after capping the bottle the contents were shaken to dissolve the sample for a period of 2 to 8 hours. The white residue present after the treatment was dissolved in 100 ml of saturated H 3 BO 3 solution. The contents were diluted and final volume was made to 250 ml and subsequently used for analysis of total potassium by flame photometry Lattice potassium The lattice potassium was calculated by deducting the sum of water soluble, exchangeable, non exchangeable from total K. 3.4 Potassium reserves in textural fractions of soil The various sized fractions of surface and subsurface soils of the cropping systems viz., coarse sand, fine sand and clay were separated by gravity sedimentation technique after destruction of organic matter and CaCO 3 removal (Piper, 1966). The procedure used for estimation of total K was followed in the determination of K content in various size fractions. 3.5 Potassium fixation capacity of soils The potassium fixation capacity of the surface and subsurface (0-15 and cm) of the soil samples under investigation was estimated by following the procedure of Ramanathan and Krishnamoorthy (1978). Initial Exchangeable K content of the soils was determined. Potassium was added to 5.0 cmol (p+) kg -1 in the form of KCl solution and soils were incubated at room temperature at field capacity moisture for two weeks.

31 Table 4. Initial soil characteristics of experimental plot of paddy-paddy cropping sequence at Kasbe camp village Parameters Soil samples depth 0-15 cm cm Coarse sand (%) Fine sand (%) Silt (%) Clay (%) Textural class Clay Clay ph (1:2.5 soil water ratio) EC (d Sm -1 ) (1:2.5 soil water ratio) OC (g.kg -1 ) Av. N (kg.. ha -1 ) Av. P 2 O 5 (kg.ha -1 ) Av. K 2 O (kg.ha -1 ) CaCO 3 (%) Exch. Ca (cmol (p + ) kg -1 ) Exch. Mg (cmol (p + ) kg -1 ) Exch. Na (cmol (p + ) kg -1 ) CEC (cmol (p + ) kg -1 ) WS-K (mg/kg) 10 (0.11) 7 (0.07) Exch-K (mg/kg) 145 (1.55) 188 (2.02) Non Exch-K (mg/kg) 415 (4.46) 493 (5.10) Lattice K (g/kg) 8.84 (95.05) 9.23 (95.64) Total K (g/kg) WS = Water Soluble; Exch = Exchangeable Note: Values in parentheses are percentage of Total K.

32 Table 5. Initial soil characteristics of experimental plot of sunflower-bengalgram cropping sequence at Gabbur village Parameters Soil samples depth 0-15 cm cm Coarse sand (%) Fine sand (%) Silt (%) Clay (%) Textural class Clay Clay ph (1:2.5 soil water ratio) EC (d Sm -1 ) (1:2.5 soil water ratio) OC (g.kg -1 ) Av. N (kg.. ha -1 ) Av. P 2 O 5 (kg.ha -1 ) Av. K 2 O (kg.ha -1 ) CaCO 3 (%) Exch. Ca (cmol (p + ) kg -1 ) Exch. Mg (cmol (p + ) kg -1 ) Exch. Na (cmol (p + ) kg -1 ) CEC (cmol (p + ) kg -1 ) WS-K (mg/kg) 6 (0.09) 4 (0.06) Exch-K (mg/kg) 88 (1.04) 108 (1.22) Non Exch-K (mg/kg) 312 (3.71) 369 (4.19) Lattice K (g/kg) 8.12 (95.16) 8.51 (94.53) Total K (g/kg) WS = Water Soluble; Exch = Exchangeable Note: Values in parentheses are percentage of Total K.

33 The exchangeable K was re-determined at the end of incubation by extracting with 1N NH 4 OAc and K in the extract was estimated by flame photometry. The K fixation capacity was determined as Initial exchangeable K Exchangeable K re determined K-fixation capacity = + Added K after equilibration 3.6 Clay mineralogical studies Mineralogical analysis of clay Sample preparation: Based on the clay per cent as determined by particle size analysis, the known amount of air dried soil was taken to have about 10 g clay in the suspension. It was treated with 1N NaOAc buffered to ph 4.5 to remove carbonates with 30% H 2 O 2 to remove organic matter and with citrate-bicarbonate-dithionite (CBD) treatment for the removal of free iron. Finally excess salts were removed by washing with 95 per cent methanol. The fractionation of soil particles was achieved after dispersing the soil completely (maintaining ph of 8.5 to 9.0) under gravity sedimentation X-ray diffractometry (i) Method: The natural clay samples after removing organic matter, iron oxides and amorphous constituents were analyzed for semi-quantitative mineralogy by X-ray diffraction. About 200 mg of clay suspension was taken and saturated with Mg and K and taken in 10 ml of distilled water to get a 2 per cent suspension. Parallel oriented aggregate specimens of the Mg and K saturated clays were prepared by spreading one per cent suspension of the clay uniformly over 4.5 x 2.5 cm glass slide. Slides were dried at room temperature under controlled humidity. The samples were subjected to X-ray diffraction analysis and the diffractograms were recorded with the following treatments. (a) Mg-saturated, (b) Mg-saturated and glycerol solvated, (c) K-saturated and(d) K- saturated and heated to 550 o C for two hours. The X-ray diffractograms were recorded with CuKα radiation (r= o A) obtained at 40KV and 20 ma TCI from a Philips PW 1140 recorder at a scanning speed of the goniometer of 220 per minute, time constant 4 and attenuation one. (ii) Interpretation of X-ray diffractograms (a) Identification of clay minerals: X-ray diffractometry is an indispensable technique for identification of crystalline mineral species of a group present in the sample. Bragg s law (n =2d sin) is the basis for X-ray diffractometry and also diffraction pattern of each crystal species is a unique sequence of diffraction maxima like a finger-prints, the pattern serves the purpose of identification of each species present unless the diffraction intensity is inadequate. Ordinarily dependence is placed on the most intense one to three diffraction peaks from basal planes for qualitative identification. The d values are calculated for all the diffraction maxima recorded in the X-ray diffractograms using tables for conversion of 20 values to dhkl for various X-ray tube target materials, viz., Cu, Fe, or Co. Several tables of diffraction spacing of crystalline substances are available. The basal spacing of layer silicates varies within limits, with the nature of interlayer cations and the salvation procedure employed. The intensity of the diffraction maxima also changes with the nature of cations and thermal pretreatments in some cases. The following five treatments are generally employed to record diffractograms: 1. Mg-saturation 2. Mg-saturation and glycol or glycerol salvation 3. K-saturation 4. K-saturation and heating to 550 o Ċ for 2 hrs.

34 For some specific studies, some special treatments (HCI dissolution, sodium citrate treatment etc.) may be required. The diagnostic criteria for the major clay mineral groups are presented below. (1) Mica group: This group of minerals is recognized by reflections of strong peaks at 10 o A peak with a tail extending towards low angle is generally recorded in soil clay minerals. Such illites are termed as degraded Illite, which are common in Indian soil clays. These are also considered as mixed layer minerals. K-saturation often removes the asymmetry and produces a strong 10 o A peak in such minerals. The di-octahedral and tri-octahedral mica is identified by the ratio of (001/002). A high ratio of the intensity of 10A/5A confirms the trio-octahedral rather than di-octahedral. Further, information concerning, whether, the mica is di-octahedral or tri-octahedral is obtained by observing (060) reflection. The (060) reflection of di-octahedral mica appears at about 1.50 o A and of tri-octahedral at o A and 1.53 o A in case of biotite. (2) Kaolin group: Minerals in this group are identified by strong basal reflection at 7.0 o A and 3.5 o A, which, disappear on heating the sample at 550 o C. The heat treatment also distinguishes it from true chlorites. Many soil chlorites also get decomposed or lose the 7 o A peak on heating at 550 C or even low temperature under such conditions dilute HCI (warm) treatment leads to correct identification. The warm HCI dissolves the chlorite along with some tri-octahedral montmorillonite and vermiculite. Halloysite of some soils give a spacing of 10.1 to 10.7 o A, but more often soil halloysites give a spacing of about 7.6 o A on Mg-saturation and glycerol salvation. Heating to 400 o Ċ decreases the spacing to 7.2 o A. Intersolvation of kaolinite and halloysite with potassium acetate gives a 14 o A spacing and this can be decreased to a diagnostic 11.6 o A spacing on washing with 10N NH 4 NO 3 solution. (3) Chlorite group: Minerals in this group are identified by a series of basal reflections at 14, 7, 4.7 and 3.5 o A, which, persist on heating the specimen at 550 o Ċ. The iron rich chlorite poses problem, particularly in presence of kaolinite. Whereas, 001 and 003 reflections are weak, the 002 and 004 reflections are relatively stronger, overlapping the 001 and 002 reflections of kaolinite. In clay chlorites a series of deflect are generally produced as a result of weathering. Defect in the structure may also cause partial expansion with glycerol as found in so called swelling chlorite. This type of imperfect chlorites are identified by the 18 o A spacing in glycerol and 14 o A spacing on heating at 550 o Ċ. Chloritised montmorillonite/vermiculite formed by fixation of Fe/Al hydroxide in interlayer space under acid conditions of weathering is also common in Indian soils. This inter-layer material can be removed by treating either with NII 4 F or Na-citrate. Prior to this treatment, minerals give a 14 o A peak and do not collapse to 10 o A on K-saturation and heating but after the interlayer material has been removed, the resultant mineral either gives a 14 o A spacing or an 18 o A spacing on glycerol salvation. (4) Smectite group: This group gives a strong reflection at 14 o A on Mg-saturation and can be isolated from rest of the 14 o A spacing on treatment with glycol/glycerol when it gives 17 o A and 18 o A, respectively. The spacing decreases on K-saturation frequently giving reflection at 12 o A. This reflection shifts to 10 o A and is usually enhanced to give a sharp peak on heating at 300 o A broad 10 o A peak even after heating at 300 o Ċ indicates that the material has Al-hydroxide or oxide interlayer countering the layer charge and causing resistance to the thermal collapse. (5) Vermiculite: Mg-saturated vermiculite give a peak between o A. K-saturated vermiculite can be distinguished from smectite or chlorite by its non-expansibility on glycerol salvation and collapsibility on K-saturation. Even the low charge vermiculite will collapse on K-saturation and heating to 300 o Ċ. True vermiculite give only a very weak second order peak at o A and medium intensity peaks at 4.79 o A and 3.60 o A. (6) Interstratified minerals: In soils mostly two types of interstratifications are found (a) a regular or ordered alteration of mineral layers in definite sequence for which the resulting super lattice spacing is additive of the basal spacing of the minerals present and their different orders.

35 (b) A completely random interstratifications, in which, the layers do not repeat themselves in any sequence but are randomly distributed in the complex. Random mixtures can be of binary, ternary or quaternary interstratifications involving two, three or four minerals. Binary random mixtures can be identified easily but the higher types are difficult to identify. 3.7 Statistical analysis The experimental data was analyzed statistically following the procedures as described by Gomez and Gomez (1984). The level of significance used in F and t test were 5 per cent. Simple correlated studies were made to understand some of the relationships between the forms of K and soil properties as well as among the forms of K.

36 4. EXPERIMENTAL RESULTS The investigations carried out on the surface and subsurface soil samples collected from different villages under paddy-paddy and sunflower-bengalgram cropping sequences and the response of paddy, sunflower and bengalgram to potassium application in the cropping sequences are presented in this chapter under the following headings: 4.1 Physico-chemical properties of the surface and subsurface soils collected from cropping sequence. 4.2 Forms and distribution of potassium in surface and subsurface soils collected from cropping sequence. 4.3 Effect of potassium application on growth and yield of crops in the paddy-paddy and sunflower-bengalgram cropping sequence. 4.4 Uptake of potassium by paddy, sunflower and bengalgram in the cropping sequence. 4.5 Potassium fixation capacity of soils of experimental site of the both cropping systems. 4.6 Potassium reserves in different size fractions of soils of experimental site of both cropping sequence 4.7 Clay mineralogy of soils of experimental site of the both cropping sequence. 4.1 Physico-chemical properties of the surface and subsurface soils collected from two different cropping sequences Physico-chemical properties of the soils of Paddy-paddy cropping sequence The particle size analysis The data on the particle size analysis are presented in the Table 6. The data revealed that the amount of clay was high in these soils. The amount of clay in the soils ranged form 40.3 to 56.7 per cent in the surface and 44.9 to 60.2 per cent in the subsurface horizons. The lowest and highest clay content was recorded in sample No. 1 of Ganjalli and sample No. 4 of Potnal village for surface and sample No. 5 of Ganjalli and sample No. 4 of Potnal village for subsurface horizons. The soils studied were clay in texture. The distribution of clay followed a definite pattern of increasing with depth in all the soils studied. The silt content of the soils ranged from 18.8 to 29.7 per cent in the surface and 18.6 and 32.9 per cent in the subsurface layer. The highest silt was recorded in sample No. 3 and No. 2 of Devsugur village for surface and subsurface and lowest in sample No. 5 of Hanchinal camp for surface and sample No. 4 of Gorebal camp for subsurface horizons. The silt content of the soils did not follow a definite pattern. The fine sand content of surface and subsurface layers recorded was in the range of 8.5 to 18.4 and 8.0 to17.9 per cent. The highest was recorded in sample No.3 of Gorebal village for surface and sample No. 2 of Araginamar camp for subsurface and lowest in sample No.3 of Kasbe camp and sample No. 3 of Vijayanager camp for surface and subsurface layer. The fine sand content did not followed a definite pattern trend with depth. The content coarse sand ranged between 9.4 to 17.6 and 6.5 to 12.2 per cent in surface and subsurface soil horizons. The lowest of 9.4 per cent was observed in sample No. 1 of Hanchinal camp for surface and 6.5 in sample No. 1 of Araginamara camp for sub surface. The highest was recorded in sample No.2 of Kasbe camp for surface and sample No.4 of Viajanagar camp for subsurface. The content of coarse sand decreased with depth Chemical properties The data on various soil chemical properties are presented in Table 7.

37 Table 6. Textural analysis of soils from paddy-paddy cropping sequence under vertisols in TBP Command area Location Sample No. Coarse sand (%) Fine sand (%) Silt (%) Clay (%) S SS S SS S SS S SS Kasbe Camp Vijayanagar Camp Kalmala Ganjalli Devasugur Note: S = Surface 0-15 cm; SS = Sub surface cm

38 Table 6 (Contd..). Textural analysis of soils from paddy-paddy cropping sequence under vertisols in TBP Command area Location Sample No. Coarse sand (%) Fine sand (%) Silt (%) Clay (%) S SS S SS S SS S SS Sirwar Harvi Neermanvi Amareshwara camp Potnal Note: S = Surface 0-15 cm; SS = Sub surface cm

39 Table 6 (Contd..). Textural analysis of soils from paddy-paddy cropping sequence under vertisols in TBP Command area Location Sample No. Coarse sand (%) Fine sand (%) Silt (%) Clay (%) S SS S SS S SS S SS Jawalgera Raithanagar Camp Araginamara Camp Gorebal Camp Hanchinal Camp Note: S = Surface 0-15 cm; SS = Sub surface cm

40 Table 7. Chemical properties of soil samples from paddy-paddy cropping sequence under vertisols in TBP Command area Location Sample ph EC (dsm -1 ) OC (g kg -1 ) CaCO 3 (%) CEC (c mol (p+) kg -1 ) No. S SS S SS S SS S SS S SS Kasbe camp Vijayanagar camp Kalmala Ganjalli Devasugur Note: S = Surface 0-15 cm; SS = Sub surface cm

41 Table 7 (Contd..). Chemical properties of soil samples from paddy-paddy cropping under vertisols in TBP Command area Location Sample ph EC (dsm -1 ) OC (g kg -1 ) CaCO 3 (%) CEC (c mol (p+) kg -1 ) No. S SS S SS S SS S SS S SS Sirwar Harvi Neermanvi Amareshwara camp Potnal Note: S = Surface 0-15 cm; SS = Sub surface cm

42 Table 7 (Contd..). Chemical properties of soil samples from paddy-paddy cropping under vertisols in TBP Command area Location Sample ph EC (dsm -1 ) OC (g kg -1 ) CaCO 3 (%) CEC (c mol (p+) kg -1 ) No. S SS S SS S SS S SS S SS Jawalgera Raithanagar Camp Araginamara Camp Gorebal Camp Hanchinal Camp Note: S = Surface 0-15 cm; SS = Sub surface cm

43 Soil Reaction The ph of the surface and subsurface layers varied from 7.9 to 9.1 and 7.9 to 9.3. The lowest ph of 7.9 was registered in sample No.1 of Devsugur for both surface and subsurface and highest in sample No.1 of Kalmala and sample No. 2 of Hanchinal camp. All the soils studied are neutral to alkaline in reaction. An increasing trend in ph values with depth was noticed in most of the soils. Electrical Conductivity The electrical Conductivity of soils ranged from 0.26 to 0.93 and 0.30 to 0.95 in surface and subsurface layers, respectively. The highest EC value was recorded in sample No. 5 of Amareswara camp for surface and subsurface depths and lowest in sample No. 3 of Raithanagar camp. EC values did not follow a definite trend of increase or decrease with depth. Organic carbon content The organic carbon content of the soils ranged from 2.5 to 8.3 in surface and 1.5 to 6.5 g kg -1 in subsurface horizons. The highest organic carbon content was observed in sample No.1 of Jawalgera for surface and subsurface and lowest in sample No.2 of Vijaynagar camp and sample No. 3 of Kasbe camp for surface and subsurface layers. The organic carbon content of soils decreased with depth. Calcium Carbonate content The calcium carbonate content of soils varied from 3.4 to 11.2 per cent in surface and 3.9 to 12.1 per cent in sub surface layer. The highest value was recorded in Amreshwara camp for sample No.1 and lowest in sample No. 3 of Ganjalli village for both surface and subsurface horizons. The soils studied are calcareous in nature. Cation Exchange Capacity (CEC) The cation exchange capacity values of the surface and subsurface soils varied from to 82.1 and to cmol(p+) kg -1. The highest CEC of 82.1 cmol (p+) kg -1 for surface soil was observed in sample No.2 of Raithanagar camp and lowest of 39.6 c mol (p+) kg -1 in sample No. 5 of Devsugur village. In subsurface layer the highest recorded was 85.6 c mol (p+) kg -1 in sample No. 1 of Harvi village and lowest of c mol (p+) kg -1 in sample No.5 of Devsugur village. The CEC of the soils followed a definite pattern with depth in all the soils studied Physico-chemical properties of the soils of sunflower-bengalgram cropping sequence The particle size analysis The data on particle size analysis of soils are presented in Table 8. The data revealed that the soils of sunflower-bengalgram sequence were clayey in texture. The clay content of the soils ranged between 37.4 to 52.1 per cent in surface and 44.2 to 58.2 per cent in subsurface horizons. The lowest was recorded in sample No. 5 of Mustur village for surface and subsurface and highest in sample No.4 of Ashapur village for surface and sample No.1 of Hosur village for subsurface horizons. The clay content of the soils increased with depth. The silt content in surface soil ranged between 19.4 to 31.2 per cent. The highest and lowest value was recorded in the sample No. 5 of Maladakal village and sample No. 3 of Kurdi village. In subsurface horizons, it varied between 20.2 to 30.2 per cent. The lowest value was recorded in sample No. 3 of Hosur village and highest in sample No. 4 of Hokrani camp. The silt content of the soils did not follow a definite trend of increase or decrease with depth The lowest fine sand content of 8.7 per cent and 9.9 per cent was noticed in sample No. 3 of Hokrani village for surface layer and sample No. 2 of Kakargal village for subsurface layer. The highest content of 20.0 per cent was recorded in sample No. 5 of Mustur and sample No.3 of Gorebal village for surface and subsurface layer. The fine sand content of the soils increased with depth in all the soils.

44 Table 8. Textural analysis of soils from sunflower-bengalgram cropping sequence under vertisols in TBP Command area Location Sample No. Coarse sand (%) Fine sand (%) Silt (%) Clay (%) S SS S SS S SS S SS Raichur Ashapur Hosur Nelahal Dinni Note: S = Surface 0-15 cm; SS = Sub surface cm

45 Table 8 (Contd..). Textural analysis of soils from sunflower-bengalgram cropping sequence under vertisols in TBP Command area Location Sample No. Coarse sand (%) Fine sand (%) Silt (%) Clay (%) S SS S SS S SS S SS Kallur Hokrani Kurdi Betadur Chikalparvi Note: S = Surface 0-15 cm; SS = Sub surface cm

46 Table 8 (Contd..). Textural analysis of soils from sunflower-bengalgram cropping sequence under vertisols in TBP Command area Location Sample No. Coarse sand (%) Fine sand (%) Silt (%) Clay (%) S SS S SS S SS S SS Gabbur Kakargal Maladkal Yermarus Mustur Note: S = Surface 0-15 cm; SS = Sub surface cm

47 The coarse sand content ranged between 10.1 to18.9 and 5.8 to 11.3 per cent in surface and subsurface layer of sunflower-bengalgram sequence. The highest value of coarse sand for surface and subsurface layer was observed in sample No. 4 of Mustur village and lowest in sample No.1 of Kurdi for surface and sample No. 3 of Hokrani village for subsurface layer. The coarse sand content decrease with depth in all the soils Chemical properties of soil Soil Reaction The data on soil chemical properties are presented in Table 9. The data indicated that the ph of the surface and subsurface layers varied from 7.5 to 9.1. The soils are neutral to alkaline in reaction. The lowest ph was registered in sample No.5 of Maladakal and Chikalparvi village and the highest value in sample No. 5 of Hikrani and Dinni for both surface and subsurface soils. The ph values increased with depth. Electrical Conductivity The electrical conductivity of soils ranged between 0.39 to 1.32 in the surface soil and it increased to 0.43 to 1.10 in subsurface layers. The highest EC value was recorded in sample No. 1 of Yermarus for surface and subsurface layers and the lowest value in sample No. 2 of Chikalparvi and sample No. 4 of Hosur village. Observed EC values did not follow a definite trend with depth. Organic Carbon content The organic carbon content of the soils ranged from 2.0 to 7.3 g kg -1 for surface and 0.80 to 6.5 g kg -1 for subsurface layers. The highest organic carbon content was recorded in sample No.1 of Kallur and the lowest in sample No.5 of Kakargal for surface and subsurface layers. The organic carbon content of soils decreased with depth. Calcium Carbonate content The calcium carbonate content of soils varied from 4.9 to per cent in surface and 6.3 to 11.3 per cent in sub surface layer. The highest per cent of CaCO 3 content was recorded in sample No.5 of Kakargal and the lowest in sample No. 3 of Maladkal village for both surface and subsurface layers. The calcium carbonate content of soils increased with depth. The soils studied are calcareous in nature. Cation Exchange Capacity (CEC) The cation exchange capacity values of the surface and subsurface soils varied from to and to cmol (p+) kg -1. The highest CEC value for surface and subsurface layers was observed in sample No.2 of Kallur and lowest value in sample No. 1 of Mustur and 5 of Yermarus. The CEC values increased with depth. 4.2 Forms and distribution of potassium in soils of cropping sequence Paddy-paddy cropping sequence The data on forms and distribution of potassium in soils of paddy-paddy cropping sequence are presented in Table 10. Water soluble potassium The water soluble potassium content of surface and subsurface layers ranged between 4 to 14 and 1 to 10 mg kg -1. The lowest and highest water soluble potassium for surface and sub surface was recorded in sample No.3 of Raitha nagar camp and sample No. 1 of Hanchinal camp and sample No.1 of Potanl and sample No. 1 of Sirwar village. The water soluble potassium content decreased with soil depth. The contribution of water soluble K to total K ranged from 0.04 to 0.18 per cent in surface and 0.04 to 0.13 per cent in subsurface layers.

48 Table 9. Chemical properties of soil samples from sunflower-bengalgram cropping sequence under vertisols in TBP Command area Location Sample ph EC (dsm -1 ) OC (g kg -1 ) CaCO 3 (%) CEC (c mol (p+) kg -1 ) No. S SS S SS S SS S SS S SS Raichur Ashapur Hosur Nelahal Dinni Note: S = Surface 0-15 cm; SS = Sub surface cm

49 Table 9 (Contd..). Chemical properties of soil samples from sunflower-bengalgram cropping sequence under vertisols in TBP Command area Location Sample ph EC (dsm -1 ) OC (g kg -1 ) CaCO 3 (%) CEC (c mol (p+) kg -1 ) No. S SS S SS S SS S SS S SS Kallur Hokrani Kurdi Betadur Chikalparvi Note: S = Surface 0-15 cm; SS = Sub surface cm

50 Table 9 (Contd..). Chemical properties of soil samples from sunflower-bengalgram cropping sequence under vertisols in TBP Command area Location Sample ph EC (dsm -1 ) OC (g kg -1 ) CaCO 3 (%) CEC (c mol (p+) kg -1 ) No. S SS S SS S SS S SS S SS Gabbur Kakargal Maladkal Yermarus Mustur Note: S = Surface 0-15 cm; SS = Sub surface cm

51 Table 10. Distribution of different forms of K in soil samples of paddy-paddy cropping sequence under vertisols in TBP Command area Location Sample WS-K (mg kg -1 ) Exch-K (mg kg -1 ) Non Exch-K (mg kg -1 ) Lattice-K (g kg -1 ) Total-K (g kg -1 ) No. S SS S SS S SS S SS S SS 1 12 (0.12 ) 9 (0.09) 155 (1.55) 188 (1.80) 515 (5.16) 533 (5.11) 9.30 (93.18) 9.69 (93.00) (0.12) 7 (0.07) 139 (1.66) 162 (1.85) 535 (6.39) 554 (6.32) 7.69 (91.87) 8.04 (91.78) Kasbe Camp 3 13 (0.13) 7 ( (1.38) 148 (1.44) 572 (5.84) 595 (5.79) 9.08 ( (92.41) (0.13) 6 (0.07) 124 (1.66) 163 (2.06) 468 (6.25) 484( 6.10) 6.88 (91.97) 7.28 (91.80) (0.10) 6 ( (1.59) 166 (1.59) 493 (4.96) 529 (5.08) 9.27 (93.35) 9.71 (93.27) (0.12) 7 (0.07) 172 (1.88) 193 (1.97) 536 (5.86) 548 (5.58) 8.42 (92.12) 9.07 (92.36) (0.07) 4 (0.04) 162 (1.70) 180 (1.80) 488 (5.13) 512 (5.13) 8.85 (93.05) 9.28 (92.68) Vijayanagar 3 8 (0.09) 5 (0.06) 146 (1.74) 173 (1.53) 498 (5.94) 526 (5.94) 7.74 (92.25) 8.15 (92.10) Camp 4 10 (0.10) 7 (0.07) 192 (2.01) 210 (2.10) 505 (5.29) 530 (5.29) 8.83 (92.55) 9.27 (92.51) (0.10) 6 (0.06) 134 (1.51) 156 (1.66) 518 (6.04) 532 (5.67) 7.92 (92.30) 8.69 (92.64) (0.18) 8 (0.10) 138 (1.93) 157 (2.00) 444 (6.22) 458 (5.85) 6.54 (91.60) 7.21 (92.08) (0.16) 6 (0.09) 143 (2.17) 176 (2.55) 492 (7.45) 528 (7.65) 5.95 (90.15) 6.19 (93.78) Kalmala 3 10 (0.13) 6 (0.07) 177 (2.31) 193 (2.36) 499 (6.51) 541 (6.62) 6.98 (91.00) 7.43 (90.94) (0.17) 5 (0.09) 169 (3.19) 187 (3.36) 565 (10.68) 584 (10.50) 4.58 (86.57) 4.78 (85.97) (0.15) 7 (0.08) 185 (2.25) 202 (2.29) 500 (6.08) 535 (6.05) 7.53 (91.50) 8.10 (91.62) (0.19) 5 (0.13) 110 (2.99) 113 (2.90) 395 (10.76) 423 (10.87) 3.17 (86.14) 3.35 (86.11) (0.14) 4 (0.08) 105 (2.42) 118 (2.49) 354 (8.18) 375 (7.29) 3.86 (89.14) 4.23 (89.42) Ganjalli 3 5 (0.09) 3 (0.05) 88 (1.73) 108 (2.01) 383 (7.52) 424 (7.91) 4.61 (90.56) 4.83 (90.11) (0.17) 4 (0.08) 95 (2.02) 103 (2.08) 398 (8.49) 415 (8.38) 4.19 (89.33) 4.43 (89.49) (0.17) 5 (0.11) 103 (2.50) 123 (2.72) 355 (8.62) 412 (9.11) 3.66 (88.83) 3.98 (88.05) (0.16) 5 (0.10) 93 (1.94) 105 (2.02) 342 (7.13) 374 (7.21) 4.33 (90.39) 4.71 (90.75) (0.17) 4 (0.10) 109 (3.22) 117 (3.00) 360 (10.65) 392 (10.07) 2.90 (85.79) 3.38 (86.88) Devasugur 3 6 (0.11) 4 (0.07) 88 (1.64) 106 (1.86) 344 (6.41) 353 (6.23) 4.92 (91.79) 5.21 (91.88) (0.21) 5 (0.12) 94 (2.47) 102 (2.49) 423 (11.13) 448 (10.92) 3.28 (86.31) 3.25 (79.27) (0.23) 5 (0.11) 98 (2.47) 108 (2.50) 371 (9.35) 392 (9.07) 3.49 (87.90) 3.82 (88.42) Note: S = Surface 0-15 cm; SS = Sub surface cm WS - Water Soluble; Exch - Exchangeable; Non Exch - Non Exchangeable *Values in parentheses are in percentage to the Total-K ; Different units are used for values

52 Table 10 (Contd..). Distribution of different forms of K in soil samples of paddy-paddy cropping sequence under vertisols in TBP Command area Location Sample WS-K (mg kg -1 ) Exch-K (mg kg -1 ) Non Exch-K (mg kg -1 ) Lattice-K (g kg -1 ) Total-K (g kg -1 ) No. S SS S SS S SS S SS S SS 1 14 (0.23) 10 (0.15) 146 (2.39) 168 (2.44) 602 (9.87) 613 (8.91) 5.34 (87.54) 6.09 (88.51) (0.11) 5 (0.06) 130 (1.63) 152 (1.85) 475 (5.96) 498 (6.07) 7.36 (92.35) 7.56 (92.08) Sirwar 3 13 (0.14) 8 (0.09) 165 (1.82) 178 (1.92) 472 (5.20 ) 492 (5.31) 8.42 (92.83) 8.58 (92.66) (0.12) 6 (0.06) 204 (2.07) 223 (2.24) 473 (4.81) 484 (4.86) 9.15 (92.99) 9.25 (92.87) (0.15) 7 (0.09) 174 (2.21) 196 (2.43) 503 (6.40) 528 (6.53) 7.27 (92.49) 7.35 (90.96) (0.10) 7 (0.07) 138 (1.60) 154 (1.72) 436 (5.05) 458 (5.11) 8.05 (93.28) 8.35 (93.09) (0.11) 8 (0.08) 152 (1.66) 167 (1.75) 587 (6.42) 610 (6.39) 8.39 (91.79) 8.76 (91.82) Harvi 3 9 (0.10) 6 (0.06) 115 (1.33) 129 (1.42) 598 (6.90) 606 (6.67) 7.95 (91.69) 8.34 (91.85) (0.16) 5 (0.07) 178 (2.82) 201 (2.92) 510 (8.08) 532 (7.72) 5.61 (88.91) 6.15 (89.25) (0.13) 5 (0.05) 184 (2.02) 196 (2.05) 485 (5.32) 512 (5.36) 8.44 (92.54) 8.84 (92.56) (0.12) 9 (0.09) 195 (2.10) 217 (2.21) 512 (5.50) 528 (5.38) 8.58 (92.26) 9.06 (92.35) (0.17) 7 (0.08) 118 (1.55) 134 (1.69) 435 (5.72) 438 (5.52) 7.03 (92.50) 7.35 (92.69) Neermanvi 3 12 (0.15) 8 (0.10) 119 (1.55) 136 (1.71) 499 (6.50) 522 (6.56) 7.05 (91.80) 7.28 (91.57) (0.13) 8 (0.08) 177 (1.88) 192 (1.95) 465 (4.94) 484 (4.91) 8.77 (93.10) 9.18 (93.10) (0.09) 5 (0.04) 145 (1.43) 166 (1.57) 415 (4.10) 434 (4.11) 9.55 (94.36) 9.95 (94.31) (0.14) 6 (0.06) 164 (1.88) 198 (2.27) 495 (5.68) 520 (5.98) 8.03 (92.30) 8.56 (92.24) (0.11) 5 (0.06) 121 (1.61) 138 (1.73) 524 (6.97) 571 (7.16) 6.87 (91.35) 7.26 (91.10) Amareshwara 3 14 (0.13) 9 (0.08) 163 (1.56) 188 (1.72) 485 (4.65) 504 (4.62) 9.77 (93.67) (93.58) camp 4 13 (0.17) 6 (0.08) 115 (1.71) 133 (1.87) 489 (7.28) 513 (7.19) 6.10 (90.77) 6.48 (90.88) (0.09) 6 (0.05) 108 (1.03) 143 (1.30) 528 (5.01) 542 (4.94) 9.88 (93.83) (93.71) (0.13) 8 (0.07) 134 (1.27) 152 (1.38) 542 (4.13) 554 (5.04) 9.87 (93.47) (93.63) (0.16) 9 (0.12) 139 (1.89) 165 (2.15) 562 (7.64) 579 (7.56) 6.65 (90.35) 6.91 (90.20) Potnal 3 12 (0.22) 7 (0.13) 152 (2.86) 175 (3.08) 554 (10.41) 568 (10.00) 4.60 (86.47) 4.93 (86.79) (0.14) 8 (0.08) 120 (1.33) 148 (1.59) 523 (5.81) 538 (5.78 ) 8.33 (92.65) 8.61 (92.58) (0.11) 6 (0.06) 112 (1.20) 139 (1.46) 565 (6.04) 593 ( (92.62) 8.72 (92.17) Note: S = Surface 0-15 cm; SS = Sub surface cm WS - Water Soluble; Exch - Exchangeable; Non Exch - Non Exchangeable *Values in parentheses are in percentage to the Total-K; Different units are used for values.

53 Table 10 (Contd..). Distribution of different forms of K in soil samples of paddy-paddy cropping sequence under vertisols in TBP Command area Location Sample WS-K (mg kg -1 ) Exch-K (mg kg -1 ) Non Exch-K (mg kg -1 ) Lattice-K (g kg -1 ) Total-K (g kg -1 ) No. S SS S SS S SS S SS S SS 1 9 (0.10) 5 (0.05) 215 (2.54) 235 (2.66) 568 (6.71) 593 (6.72) 7.67 (90.66) 7.99 (90.58) (0.09) 2 (0.02) 198 (2.71) 222 (2.91) 485 (6.27) 508 (6.66) 6.61 (90.55) 6.90 (90.43) Jawalgera 3 12 (0.12) 6 (0.06) 185 (1.91) 212 (2.12) 462 (4.79) 492 (4.92) 8.98 (93.15) 9.29 (92.90) (0.06) 3 (0.36) 174 (2.21) 199 (2.41) 575 (7.32) 603 (7.31) 7.10 (94.78) 7.44 (90.29) (0.06) 2 (0.02) 208 (2.31) 236 (2.47) 515 (5.73) 528 (5.55) 8.25 (91.87) 8.75 (91.91) (0.08) 3 (0.02) 203 (2.06) 224 (2.19) 536 (5.44) 558 (5.46) 9.11 (92.39) 9.44 (92.36) (0.10) 5 (0.06) 212 (2.91) 235 (3.07) 487 (6.68) 510 (6.67) 6.58 (90.26) 6.90 (90.19) Raithanagar 3 4 (0.04) 1 (0.01) 205 (2.22) 239 (2.58) 478 (5.18) 506 (5.46) 8.53 (92.52) 8.52 (91.90) Camp 4 5 (0.05) 2 (0.02) 178 (2.03) 201 (2.21) 510 (5.82) 532 (5.86) 8.08 (92.13) 8.35 (91.96) (0.06) 3 (0.03) 184 (1.98) 196 (2.05) 498 (5.37) 525 (5.49) 8.58 (92.56) 8.84 (92.46) (0.07) 2 (0.02) 225 (2.86) 258 (3.14) 442 (5.62) 468 (5.69) 7.20 (91.48) 7.59 (92.33) (0.11) 6 (0.06) 208 (2.33) 224 (2.34) 534 (5.99) 558(5.83) 8.17 (91.59) 8.78 (91.75) Araginamara 3 5 (0.05) 3 (0.03) 169 (1.92) 182 (2.02) 599 (6.79) 631 (7.01) 8.05 (91.27) 8.18 (90.89) Camp 4 6 (0.07) 6 (0.07) 198 (2.63) 216 (2.77) 475 (6.30) 505 (6.47) 6.85 (90.96) 7.08 (90.77) (0.06) 5 (0.05) 205 (2.16) 228 (2.93) 518 (5.46) 544(5.53) 8.75 (92.29) 9.06 (92.07) (0.12) 3 (0.03) 194 (2.50) 215 (2.64) 485 (6.24) 512 (6.29) 7.08 (91.11) 7.40 (91.02) (0.09) 5 (0.05) 191 (1.95) 228 (2.22) 524 (5.34) 578 (5.63) 9.10 (96.60) 9.44 (92.10) Gorebal Camp 3 13 (0.13) 8 (0.08) 213 (2.15) 228 (2.25) 495 (4.99) 534 (5.28) 9.20 (92.74) 9.35 (92.39) (0.08) 4 (0.04) 175 (1.80) 203 (2.03) 589 (6.05) 613 (6.14) 8.97 (92.09) 9.16 (91.78) (0.10) 6 (0.07) 238 (3.20) 265 (3.40) 528 (7.12) 543(6.97) 6.65 (89.62) 6.98 (89.60) (0.06) 1 (0.01) 215 (3.26) 224 (3.20) 582 (8.82) 624(8.91) 5.80 (87.88) 6.15 (87.85) (0.06) 2 (0.02) 195 (2.69) 215 (2.83) 562 ( (7.72) ) 6.80 (89.47) Hanchinal Camp 3 6 (0.07) 4 (0.04) 218 (2.66) 235 (2.74) 544 (6.63) 588(6.85) 7.42 (90.37) 7.76 (90.33) (0.10) 5 (0.05) 188 (2.10) 218 (2.35) 482 (5.39) 510(5.50) 8.26 (92.39) 8.54 (92.12) (0.11) 4 (0.04) 148 (1.67) 187 (2.05) 545 (6.15) 593(6.50) 8.16 (92.10) 8.34 (91.44) Note: S = Surface 0-15 cm; SS = Sub surface cm WS - Water Soluble; Exch - Exchangeable; Non Exch - Non Exchangeable *Values in parentheses are in percentage to the Total-K; Different units are used for values.

54 Exchangeable Potassium The fraction of exchangeable potassium content varied from 88 to 238 mg kg -1 and 103 to 265 mg kg -1 for surface and subsurface layers, respectively. The highest content of exchangeable K 238 mg kg -1 in surface and 265 mg kg -1 in subsurface was noticed in sample No. 5 of Gorebal village and the lowest of 88 and 103 mg kg -1 was recorded in sample No.3 and No.4 of Ganjalli village for surface and subsurface layers. The per cent contribution of exchangeable K to the total K varied from 1.03 to 3.26 and 1.30 to 3.40 from surface and subsurface layers. This fraction was found to follow the definite distribution pattern of increasing with depth. Non exchangeable potassium The non exchangeable potassium content in surface and subsurface layers varied between 342 to 602 mg kg -1 and 374 to 631 mg kg -1, respectively. The lowest value of non exchangeable K was recorded in surface and subsurface layers of sample No.1 of Devsugur village and the highest in sample No.1 of Sirwar and sample No.1 of Hanchinal camp. The contribution of non exchangeable K to total K varied from 4.10 to per cent in surface and 4.11 to per cent in subsurface layers, respectively. The non exchangeable K content of soils increased with depth. Lattice Potassium The lattice K fraction followed a definite pattern with respect to depth wise distribution of potassium. The content of lattice K in surface and subsurface layers varied from 2.90 to 9.88 g kg -1 and 3.25 to g kg -1. The highest value recorded was in sample No. 5 of Amreswara camp for both layers and lowest in sample No.2 and sample No. 4 of Devsugur for surface and subsurface soils. The lattice K accounted for major portion of the total K exceeding 85 per cent. The lowest and highest contribution of lattice K to total K was and per cent in surface and and in subsurface layers of the both the cropping sequence. The content of lattice K increased with soil depth. Total Potassium The Total K content in surface and subsurface layers of soils ranged from 3.38 to 10.6 g kg -1 and 3.89 to 11.0 g kg -1. An increase in content of Total K with depth was noticed in the soil samples of all the villages. The lowest total K content was recorded in sample No. 2 of Devsugur village and highest in sample No. 1 of Potnal for surface and subsurface layers Sunflower-bengalgram cropping sequence The data on forms and distribution of potassium in soils of sunflower-bengalgram cropping sequence are presented in Table 11. Water soluble potassium The water soluble potassium content of surface and subsurface layers ranged from 3 to 12 and 1 to 9 mg kg -1. The lowest water soluble potassium content for surface was recorded in sample No.1 of Hosur, sample No.2 of Nelehal and Yermarus and highest in sample No.4 of Kallur village. The water soluble potassium content decreased with depth. The contribution of water soluble K to total K ranged from 0.04 to 0.18 per cent in surface and 0.04 to 0.13 per cent in subsurface layers. Exchangeable potassium The fraction of exchangeable potassium content varied from 75 to 138 mg kg -1 and 92 to 158 mg kg -1 for surface and subsurface layers. The highest content of exchangeable K, 138 mg kg -1 for surface and 158 mg kg -1 for subsurface layer was noticed in sample No. 2 of Betadur and sample No.4 of Ashapur. The lowest content was recorded in sample No.4 of Raichur for surface and sample No.1 of Gabbur for sub- surface. The per cent contribution of exchangeable K to total K ranged from 1.25 to 2.48 and 1.40 to 2.82 from surface and subsurface layers. However, this fraction was found to follow the definite distribution pattern of increasing with depth.

55 Non exchangeable potassium The non exchangeable potassium content in surface and subsurface layers varied from 285 to 468 mg kg -1 and 330 to 494 mg kg -1. The lowest non exchangeable potassium content recorded for surface and subsurface layers was in sample No.2 of Gabbur and sample No.1 of Chikalparvi village. The highest content non exchangeable potassium was recorded in sample No.3 of Betadur for both surface and subsurface. The contribution of non exchangeable K to total K varied from 4.30 to 9.06 per cent in surface and 4.17 to 8.68 per cent in subsurface layers. The non exchangeable K content of soils increased with depth. Lattice Potassium The lattice K fraction followed a definite pattern of distribution of potassium. The content of lattice K in surface and subsurface layers varied from 4.28 to 6.88 g kg -1 and 4.58 to 6.97 g kg -1, respectively. The highest recorded was in sample No. 1 of Kallur for both layers and lowest in sample No.2 of Hosur. The lattice K accounted for major portion of the total K exceeding 85 per cent. The lowest and highest contribution of lattice K to total K was and per cent in surface and and per cent in subsurface layers. The content of lattice K increased with depth in all the samples studied. Total Potassium The Total K content in surface and subsurface layers of soils ranged from 4.74 to 7.32 g kg -1 and 5.12 to 7.64 g kg -1. An increase in content of total K with soil depth was noticed in the soil samples of all the villages. The lowest total K was recorded in sample No. 2 of Nelehal village and sample No. 2 of Hosur and highest in sample No. 1 of Kallur and sample No. 3 of Raichur for surface and subsurface soil. 4.3 Response of crops to K application in cropping sequences It is a well known fact the balanced application of nutrients (RD NPK) has a greater role in enhancing the growth and yield in most of the crops. As the farmers are adopting imbalanced application of NPK fertilizers, which includes double the recommended doses of nitrogen, recommended P and 25 per cent of recommended K for paddy under irrigated condition and 50 to 75 per cent of recommended doses of N and P without K for sunflower and bengalgram under rainfed condition resulting in mining of potassium from soil. Hence, the results of the response of crops to different levels of potassium fertilization along with recommended N and P were compared with the farmers practice, instead with control or RD N or RD N and P, to get more precise information on the benefits of balanced application of fertilizers Response of paddy to K application in paddy-paddy cropping sequence Kharif-2004: The results of the experiments on application of different levels of potassium to paddy are presented in Table 12. The data revealed that application of 100 per cent K along with recommended N and P (RDF) had significantly influenced the growth and yield parameters compared to the treatments received no K. The number of tillers per hill increased significantly from 15.8 in farmers practice to 19.2 due to application of 100 per cent K. However, there was no significant difference between the treatments received 50, 75 and 100 per cent K. The results are on par. The number of tillers recorded in control, RD N alone and RD N and P was 7.0, 12.5 and 14.3 respectively. The seed test weight (1000 seeds) differed significantly with application of potassium. The test weight recorded in the farmer s practice was g which increased significantly to g in the treatment received 100 per cent K along with RD NP. The test weight recorded in treatments received 50 and 75 per cent K was g and g respectively. However, there was no significant difference between treatments with 75 and 100 per cent K application. The grain yield of paddy differed significantly between the treatments with and without K application. The grain yield in control was 3193 kg ha -1 which increased significantly to 4706 kg ha -1 and 5378 kg ha -1 with application of RD N and RD N and P.

56 Table 11. Distribution of different forms of K in soil samples of sunflower-bengalgram cropping sequence under vertisols in TBP Command area Location Sample WS-K (mg kg -1 ) Exch-K (mg kg -1 ) Non Exch-K (mg kg -1 ) Lattice-K (g kg -1 ) Total-K (g kg -1 ) No. S SS S SS S SS S SS S SS 1 5 (0.07) 2 (0.03) 88 (1.34) 120 (1.68) 365 (5.57) 412 (5.79) 6.09 (92.98) 6.29 (92.22) (0.07) 1 (0.02) 107 (1.88) 124 (1.99) 388 (6.82) 422 (6.78) 5.39 (91.51) 5.67 (91.15 ) Raichur 3 8 (0.11) 2 (0.02) 98 (1.38) 116 (1.51) 402 (5.66) 445 (5.82) 6.59 (92.82) 6.88 (92.47) (0.10) 2 (0.03) 75 (1.28) 109 (1.72) 368 (6.26) 398 (6.29) 5.43 (92.34) 5.72 (91.81) (0.09) 2 (0.03) 78 (1.53) 94 (1.61) 325 (6.37) 385 (6.58) 4.69 (91.96) 4.95 (91.16) (0.11) 4 (0.05) 110 (1.79) 122 (1.82) 365 (5.94) 396 (5.89) 5.96 (92.55) 6.20 (92.26) (0.09) 3 (0.04) 89 (1.25) 115 (1.54) 311 (4.37) 338 (4.52) 6.82 (94.46) 7.02 (93.85) Ashapur 3 6 (0.09) 4 (0.06) 116 (1.84) 132 (1.93) 355 (5.63) 402 (5.88) 6.03 (92.63) 6.29 (92.10) (0.12) 4 (0.05) 135 (2.06) 158 (2.22) 345 (5.27) 386 (5.44) 6.36 (92.84) 6.55 (92.25) (0.07) 4 (0.06) 126 (2.45) 156 (2.66) 402 (7.80) 438 (7.47) 5.09 (91.71) 5.26 (89.76) (0.06) 1 (0.01) 95 (1.93) 110 (2.04) 347 (7.04) 377 (6.98) 4.49 (91.08) 4.71 (90.57) (0.08) 1 (0.01) 112 (2.34) 122 (2.38) 384 (8.03) 415 (8.10) 4.28 (89.54) 4.58 (89.45) Hosur 3 5 (0.08) 3 (0.04) 83 (1.43) 95 (1.40) 365 (7.63) 399 (5.91) 5.68 (92.36) 6.04 (92.35) (0.15) 5 (0.08) 98 (1.83) 120 (2.05) 458 (8.54) 466 (7.98) 5.10 (90.10) 5.25 (89.90) (0.16) 6 (0.09) 114(1.85) 133 (2.00) 423 (6.87) 445 (6.70) 5.61 (91.07) 6.06 (91.26) ( 0.10) 1 (0.01) 98 (1.66) 182 (2.82) 427 (7.24) 451 (6.99) 5.37 (91.01) 5.72 (90.07) (0.06) 2 (0.03) 118 (2.48) 134 (2.58) 288 (6.08) 333 (6.40) 4.33 (91.35) 4.73 (90.96) Nelahal 3 4 (0.09) 2 (0.03) 79 (1.55) 102 (1.81) 463 (9.06) 488 (8.68) 4.56 (89.23) 4.83 (89.11) (0.05) 3 (0.04) 96 (1.35) 112 (1.57) 450 (6.32) 462 (6.21) 6.57 (92.28) 6.85 (92.19) (0.07) 3 (0.04) 115 (1.72) 133 (1.85) 298 (4.46) 332 (4.61) 6.46 (93.90) 6.73 (93.47) (0.07) 2 (0.03) 117 (2.20) 139 (2.46) 336 (6.32) 338 (5.99) 4.86 (91.35) 5.16 (61.49) (0.09) 2 (0.03) 125 (2.46) 137 (2.40) 410 (8.07) 435 (7.60) 4.74 (89.77) 5.15 (90.03) Dinni 3 5 (0.08) 3 (0.04) 118 (1.93) 140 (2.10) 418 (6.83) 436 (6.56) 5.58 (91.18) 5.87 (91.00) (0.13) 5 (0.08) 97 (1.81) 99 (1.66) 315 (5.89) 336 (5.67) 4.93 (92.15) 5.49 (92.58) (0.07) 3 (0.05) 124 (2.43) 143 (2.58) 346 (6.78) 388 (7.00) 4.63 (90.78) 4.91 (90.25) Note: S = Surface 0-15 cm; SS = Sub surface cm WS - Water Soluble; Exch - Exchangeable; Non Exch - Non Exchangeable *Values in parentheses are in percentage to the Total-K; Different units are used for values.

57 Table 11 (Contd..) Distribution of different forms of K in soil samples of sunflower-bengalgram cropping sequence under vertisols in TBP Command area Location Kallur Hokrani Kurdi Betadur Chikalparvi Sample WS-K (mg kg -1 ) Exch-K (mg kg -1 ) Non Exch-K (mg kg -1 ) Lattice-K (g kg -1 ) Total-K (g kg -1 ) No. S SS S SS S SS S SS S SS 1 10 (0.13) 8 (0.11) 120 (1.64) 142 (1.91) 315 (4.30) 342 (4.59) 6.88 (93.99) 6.97( 93.56) (0.21) 8 (0.11) 97 (1.46) 122 (1.77) 350 (5.27) 382 (5.54) 6.18 (93.07) 6.40 (92.75) (0.12) 6 (0.90) 88 (1.39) 106 (1.59) 310 (4.90) 333 (5.00) 5.92 (93.52) 6.21 (93.38) (0.22) 9 (0.15) 95 (1.73) 109 (1.88) 338( 6.16) 366 (6.31) 5.04 (91.97) 5.32 (91.72) (0.15) 4 (0.06) 94 (1.48) 110 (1.70) 332 (5.24) 365 (5.63) 5.91 (93.22) 6.00 (92.59) (0.12) 4 (0.06) 130 (2.30) 142 (2.42) 365 ( (6.75) 5.16 (91.16) 5.33 (90.80) (0.14) 5 (0.08) 80 (1.45) 115 (2.04) 411 (7.50) 434 (7.70) 4.98 (90.88) 5.09 (90.25) (0.17) 7 (0.10) 96 ( 1.51) 113 (1.66) 405 (6.38) 440 (6.49) 5.84 (91.97) 6.22 (91.74) (0.15) 4 (0.06) 105 (1.72) 128 (1.96) 345 (5.65) 374 (5.74) 5.64 (92.46) 6.01 (92.18) (0.11) 4 (0.06) 96 (1.63) 116 (1.86) 392 (6.66) 418 ( (91.67) 5.68 (91.32) (0.18) 7 (0.09) 85 (1.24) 110 (1.52) 347 (5.06) 382 (4.17) 6.41 (93.58) 6.74 (93.09) (0.18) 6 (0.10) 92 (1.62) 102 (1.74) 364 (6.41) 404 (6.90) 5.21 (91.73) 5.34 (91.28) (0.16) 6 (0.09) 95 (1.53) 99 (1.51) 465 (7.50) 488 (7.45) 5.63 (90.81) 5.96 (90.99) (0.13) 5 (0.08) 108 (1.80) 120(1.95) 445 (7.44) 466 (7.57) 5.42 (90.64) 5.56 (90.40) (0.15) 6 (0.11) 94 (1.79) 113 (2.09) 425 (8.11) 448 (8.29) 4.71 (89.88) 4.83 (89.44) (0.15) 4 (0.07) 89 (1.67) 110 (1.98) 397 (7.46) 432 (7.78) 4.83 (90.78) 5.00 (90.10) (0.10) 3 (0.05) 138 (2.32) 152 (2.37) 388 (6.52) 425 (6.62) 5.42 (91.09) 5.84 (90.96) (0.15) 5 (0.08) 89 (1.51) 105 (1.68) 468 (7.93) 494 (7.90) 5.33 (90.33) 5.65 (90.40) (0.21) 6 (0.11) 86 (1.69) 110 (1.98) 350 (6.86) 385 (6.95) 4.65 (91.18) 5.04 (90.97) (0.08) 4 (0.06) 105 (1.82) 130 (2.11) 397 (6.87) 422 (6.86) 5.27 (91.18) 5.59 (90.89) (0.17) 8 (0.11) 97 (1.52) 119 (1.71) 296 (4.63) 330 (4.76) 5.99 (93.59) 6.47 (93.39) (0.13) 6 (0.09) 95 (1.41) 117 (1.69) 442 (6.56) 478 (6.91) 6.19 (91.83) 6.32 (91.33) (0.14) 5 (0.06) 98 (1.40) 110 (1.47) 398 (5.67) 428 (5.72) 6.51 (92.73) 6.94 (92.78) (0.16) 6 (0.10) 97 (1.64) 115 (1.94) 410 (6.91) 446 (7.19) 5.41 (91.23) 5.63 (90.80) (0.10) 3 (0.05) 84 (1.45) 110 (1.80) 445 (7.70) 488 (7.97) 5.25 (90.83) 5.52 (90.19) Note: S = Surface 0-15 cm; SS = Sub surface cm WS - Water Soluble; Exch - Exchangeable; Non Exch - Non Exchangeable *Values in parentheses are in percentage to the Total-K; Different units are used for values.

58 Table 11 (Contd..) Distribution of different forms of K in soil samples of sunflower-bengalgram cropping sequence under vertisols in TBP Command area Location Gabbur Kakargal Maladkal Yermarus Mustur Sample WS-K (mg kg -1 ) Exch-K (mg kg -1 ) Non Exch-K (mg kg -1 ) Lattice-K (g kg -1 ) Total-K (g kg -1 ) No. S SS S SS S SS S SS S SS 1 9 (0.16) 6 (0.13) 88 (1.56) 92 (1.50) 400 (7.08) 425 (6.94) 5.15 (91.15) 5.58 (91.17) (0.20) 8 (0.14) 97 (1.84) 102 (1.73) 285 (5.40) 334 (5.66) 4.89 (92.61) 5.46 (92.54) (0.12 ) 3 (0.04) 98 (1.36) 110 (1.53) 342 (5.22) 375 (5.21) 6.10 (93.12) 6.71 (93.19) (0.09) 3 (0.04) 96 (1.48) 105 (1.47) 390 (6.03) 410 (5.73) 5.98 (92.43) 6.63 (92.72) (0.14) 5 (0.07) 89 (1.42) 98 (1.43) 317 (5.07) 332 (4.85) 5.84 (93.44) 6.41 (93.71) (0.13) 5 (0.08) 113 (1.78) 122 (1.92) 360 (6.04) 388 (6.11) 5.48 (91.95) 5.82 (91.80) (0.07) 2 (0.03) 88 (1.27) 105 (1.50) 365 (5.65) 390 (5.58) 5.99 (92.87) 6.48 (92.83) (0.10) 5 (0.07) 95 (1.38) 103 (1.40) 415 (6.01) 442 (6.01) 6.38 (92.46) 6.80 (92.51) (0.20) 6 (0.11) 95 (1.95) 110 (2.03) 405 (8.30) 418 (7.74) 4.37 (89.55) 4.87 (90.18) (0.13) 4 (0.07) 96 (1.76) 106 (1.82) 323 (5.94) 345 (5.93) 5.04 (92.65) 5.39 (92.61) (0.17) 7 (0.11) 85 (1.44) 110 (1.73) 398 (6.75) 422 (6.65) 5.41 (91.69) 5.81 (91.50) (0.14) 3 (0.05) 98 (1.70) 102 (1.64) 368 (6.37) 393 (6.32) 5.31 (91.86) 5.72 (91.96) (0.14) 4 (0.06) 92 (1.62) 99 (1.59) 365 (6.43) 396 (6.37) 5.22 (91.90) 5.72 (91.96) (0.10) 4 (0.07) 88 (1.69) 110 (1.85) 337 (6.51) 365 (6.14) 4.74 (91.51) 5.46 (91.91) (0.06) 3 (0.04) 96 (1.50) 108 (1.55) 378 (5.91) 396 (5.70) 5.92 (92.50) 6.44 (92.66) (0.12) 4 (0.06) 97 (1.64) 112 (1.71) 412 (6.98) 430 (6.56) 5.38 (91.19) 6.00 (91.60) (0.06) 1 (0.02) 112 (2.17) 130 (2.33) 382 (7.43) 404 (7.24) 4.64 (90.27) 5.05 (90.50) (0.15) 5 (0.08) 108 (2.02) 115 (1.97) 360 (6.74) 374 (6.39) 4.86 (91.01) 5.36 (91.62) (0.14) 3 (0.06) 102 (2.06) 110 (2.06) 345 (6.96) 375 (7.02) 4.50 (90.90) 4.85 (90.82) (0.18) 4 (0.07) 105 (2.14) 122 (2.25) 365 (7.44) 382 (7.04) 4.42 (90.20) 4.91 (90.59) (0.13) 4 (0.07) 122 (2.31) 139 (2.36) 350 (6.63) 384 (6.51) 4.80 (90.90) 5.37 (91.01) (0.14) 6 (0.08) 115 (1.79) 127 (1.81) 410 (6.39) 430 (6.14) 5.89 (91.74) 6.44 (92.00) (0.08) 3 (0.04) 98 (1.57) 115 (1.65) 448 (7.17) 458 (6.61) 5.70 (91.20) 6.35 (91.63) (0.08) 2 (0.03) 117 (1.88) 135 (1.94) 332 (5.33) 358 (5.15) 5.77 (92.77) 6.46 (92.95) (0.07) 2 (0.03) 124 (2.28) 140 (2.30) 365 (6.70) 392 (6.43) 4.96 (91.00) 5.57 (91.31) Note: S = Surface 0-15 cm; SS = Sub surface cm WS - Water Soluble; Exch - Exchangeable; Non Exch - Non Exchangeable *Values in parentheses are in percentage to the Total-K; Different units are used for values

59 Table 12. Effect of potassium management practices on growth and yield of kharif paddy under vertisols in TBP Command area Treatments No. of tillers per hill Test Weight (g) Grain yield (kg ha -1 ) Straw yield (kg ha -1 ) K-2004 K-2005 Pooled K-2004 K-2005 Pooled K-2004 K-2005 Pooled K-2004 K-2005 Pooled T 1 - Control T 2 - Farmer s practice T 3 - RD N alone T 4 - RD N and P T 5 - RD NP + 50% K T 6 - RD NP + 75% K T 7 - RD NP + 100% K S. Em± CD at 5% Note: K- Kharif

60 Where as in farmer s practice with imbalanced use of NPK fertilizers, the yield recorded was 5492 kg ha -1 which increased significantly to 6059, 6392 and 6442 kg ha -1 in treatments received 50, 75 and 100 per cent K along with RD N and P indicating the need for balanced application of nutrients. However, there was no significant difference in grain yield between treatments received 50, 75 and 100 per cent K application was noticed. The straw yield of paddy increased with increasing levels of K application. The straw yield recorded in control, RD N alone and RD N and P was 4202, 5918 and 6553 kg ha -1 respectively, which differed significantly with treatments received different levels of K application. The straw yield recorded in farmer s practice was 7171 kg ha -1 which increased significantly to 7428, 7598 and 7879 kg ha -1 due to 50, 75 and 100 per cent K application. However, no significant difference in straw yield was observed between treatments received the K application. Kharif-2005: The results of the experiment on application of different levels of potassium to paddy are presented in Table12. The data revealed that the number of tillers per hill, test weight, grain yield and straw yield differed significantly due to application of different levels of potassium. The number of tillers per hill recorded was 15.3 in farmer s practice which increased to 18.8 due applications of 100 per cent K. The number of tillers recorded in 50 and 75 per cent K application was 18 and 18.6 respectively. There was no significant difference between treatments received 50, 75 and 100 per cent K application. The number of tillers decreased significantly in the treatments without K application The test weight differed significantly with application of potassium. The test weight recorded in farmer s practice was g which increased to g in the treatment received RDF. However, there was no significant difference in test weight of grains between treatments received 50, 75 and 100 per cent K application. The treatments which had no K application, the test weight of grains decreased significantly. The grain yield of paddy increased significantly from 5555 kg ha -1 in farmer s practice to 5812, 6149 and 6281 kg ha -1 with 50, 75 and 100 per cent K application. However, there was no significant difference in yield between treatments received 75 and 100 per cent K application. The yield of paddy decreased significantly in the treatments without K application. The yield recorded was 2849, 4465 and 5283 kg ha -1, respectively. The straw yield of paddy increased significantly with increasing levels of K application. The straw yield recorded in farmer s practice was 7013 kg ha -1 which increased significantly to 7366, 7667 and 7549 kg ha -1, respectively in the treatments with 50, 75 and 100 per cent K. However, there was no significant difference in straw yield between the treatments received 50, 75 and 100 per cent K application. The kharif pooled data indicated (Table 12) that the number of tillers, test weight, grain and straw yield differed significantly with application of different levels of potassium. The mean grain yield in farmers practice was 5573 kg ha -1, which increased significantly to 5936, 6271 and 6330 kg ha -1 with application of 50, 75 and 100 per cent K. The mean straw yield obtained in farmer s practice was 7092 kg ha -1, which increased to 7391, 7633 and 7714 kg ha -1 in the treatments with 50, 75 and 100 per cent K application. However, the results of grain and straw yields are on par with each other at 50, 75 and 100 per cent K application. The grain and straw yield of paddy decreased significantly in the treatments without K application. Rabi : The results of the experiment on application of different levels of potassium to paddy are presented in Table 13. The data revealed that the crop has responded to the application of potassium along with recommended N and P. The application of K had a significant influence on the growth and yield parameters of paddy. The number of tillers per hill increased significantly from 16.3 in farmers practice to 16.8, 18.6 and 18.5 with application of 50, 75 and 100 per cent K along with recommended N and P. However, there was no significant difference between treatments received 50, 75 and 100 per cent K. The results are on par with each other. In the treatments without K, the number of tillers decreased significantly.

61 General view of the Expt. Plot Recommended N alone Recommended N and P Plate1. General view of the experimental plot of paddy crop

62 Farmer s practice Recommended NP + 50% k Plate 1. Contd Recommended N, P and K

63 The test weight recorded in farmer s practice was g, which increased significantly to18.03 g and g with 75 and 100 per cent K application. However, there was no significant difference in test weight between the treatments with 75 and 100 per cent K application. The test weight of the grains decreased significantly in the treatments without K fertilization. The grain yield of paddy differed significantly due to application of different levels of potassium. It was 5527 kg ha -1 in farmer s practice, which significantly increased to 6141 kg ha -1 due to application of 100 per cent K with RD N and P. However, no significant difference in yield was observed among the treatments of 50, 75 and 100 per cent K application. The grain yield of paddy decreased significantly in treatments control, RD N and RD N and P. The yield recorded was 3258, 4359 and 5484 kg ha -1, respectively. The straw yield recorded in farmer s practice was 7400 kg ha -1, which increased significantly to 7846 kg ha -1 with 100 per cent K application. However, there was no significant difference in straw yield between the treatments T 4, T 5, T 6 and T 7. Rabi : The results of the experiment on application of different levels of potassium to paddy are presented in Table 13. The data revealed that the number of tillers per hill, test weight, grain yield and straw yield differed significantly due to application of different levels of potassium. The number of tillers per hill and test weight recorded in farmer s practice was 17.3 and which increased to 19.3 and 19.5 due to 100 per cent K application. However, the number of tillers and test weight of grains decreased significantly in the treatments without K application. The grain yield of paddy significantly increased from 5110 kg ha -1 in farmers practice to 5820 kg ha -1 in the treatment received RDF. However, there was no significant difference between treatments received the 75 and 100 per cent K. The results are on par with each other. In the treatments without K the yields were decreased significantly. The rabi pooled data on the grain and straw yield of paddy revealed that the mean grain and straw yield differed significantly with application of different levels of potassium (Table 13). The grain yield in farmer s practice was 5319 kg ha -1 which increased significantly to 5980 kg ha -1, the straw yield from 7299 kg ha -1 to 7635 kg ha -1 with application of 100 per cent K. However, the results of grain and straw yields are on par with each other at 50, 75 and 100 per cent K. The grain and straw yield of paddy decreased significantly in the treatments without K application Response of sunflower to K application in sunflower-bengalgram sequence Kharif- 2004: The results of the experiment on response of sunflower to different levels of potassium are presented in Table14. The data indicated that the crop has responded to the application of potassium. The head diameter, test weight (100 seeds), grain and straw yield and oil content differed significantly due to application of K. The head diameter increased from 11.3 cm farmers practice to 16.9 cm and the test weight from 3.90 g to 5.27 g due to K application. The grain yield in farmers practice was 850 kg ha -1 which increased significantly to 1113, 1130 and 1136 kg ha -1 with application 50, 75 and 100 per cent K application along with RD N and P. But there was no significant difference between treatments received 50, 75 and 100 per cent K application. The straw yield increased from 1178 kg ha -1 in farmers practice to 1606 kg ha -1 with application of 75 per cent potassium. However, no significant difference in straw yield was observed between the treatments received 50, 75 and 100 per cent K application. The highest oil content in seeds per cent was recorded in the treatment with 100 per cent K along with RD N and P. However, there was no significant difference in oil content was observed between the treatments received 50, 75 and 100 per cent K application. Kharif-2005: The results of the field experiment on response of sunflower to different levels of potassium are presented in Table14. The results revealed that the head diameter, test weight, grain and straw yield and oil content differed significantly due to different levels of application of K. The head diameter increased from 11.5 cm in farmers practice to 15.9 cm and test weight from 3.99 g to 6.04 g due to75 per cent K application.

64 Table 13. Effect of potassium management practices on growth and yield of rabi paddy under vertisols in TBP Command area Treatments Rabi No. of tillers per hill Test Weight (g) Grain yield (kg ha -1 ) Straw yield (kg ha -1 ) Rabi Pooled Rabi Rabi Pooled Rabi Rabi Pooled Rabi Rabi Pooled T 1 - Control T 2 - Farmer s practice T 3 - RD N alone T 4 - RD N and P T 5 - RD NP + 50% K T 6 - RD NP + 75% K T 7 - RD NP + 100% K S. Em± CD at 5% R rabi

65 Table 14. Effect of potassium management practices on growth and yield of kharif sunflower under vertisols in TBP Command area Treatments Head diameter (cm) Test Weight (g) Grain yield (kg ha -1 ) Straw yield (kg ha -1 ) Oil content (%) K-2004 K-2005 Pooled K-2004 K-2005 Pooled K-2004 K-2005 Pooled K-2004 K-2005 Pooled K-2004 K-2005 Pooled T 1 - Control T 2 - Farmer s practice T 3 - RD N alone T 4 - RD N and P T 5 - RD NP + 50% K T 6 - RD NP + 75% K T 7 - RD NP + 100% K S. Em± CD at 5% Note: K- Kharif

66 General view of the Expt. Plot Recommended N alone Recommended N and P Plate.2 General view of the experimental plot of sunflower crop

67 Farmer s practice Recommended NP + 50% K Recommended N, P and K Plate 2. Contd..

68 The grain yield in farmers practice was 780 kg ha -1 which increased to 1027 kg ha -1. The straw yield from 1082 kg ha -1 to 1482 kg ha -1 due to application of 100 per cent potassium along with RD N and P. However, no significant difference in grain and straw yield was observed between treatments received 50, 75 and 100 per cent K. The results are on par with each other. The oil content of the seeds increased with increasing levels of K application. The highest oil content of per cent was recorded in treatment with RDF. However, no significant difference in oil content was observed between the treatments received 50, 75 and 100 per cent K. The per cent oil content recorded under corresponding treatments were 36.18, and 37.54, respectively. The pooled data of the experiment on response of sunflower to different levels of potassium is presented in Table 14. The results revealed that the mean grain and straw yield and oil content of seeds increased with increasing levels of K application. The grain yield in farmer s practice was 815 kg ha -1 and which increased to 1063, 1077 and 1082 kg ha -1 with 50, 75 and 100 per cent K application along with RD N and P. However no significant difference in grain yield was observed between the treatments received 50, 75 and 100 per cent K application. The straw yield increased from 1130 kg ha -1 in farmer s practice to 1540 kg ha -1 with application of 100 per cent potassium. However, no significant difference in straw yield was observed between the treatments received 50, 75 and 100 per cent K. The oil content of seeds differed significantly with increasing levels of K application. The highest oil content of per cent was observed with application of RDF. However, no significant difference in oil content was observed between the treatments received 50, 75 and 100 per cent K. The oil content recorded in farmers practice was per cent Response of bengalgram to K application in sunflower-bengalgram sequence Rabi : The results of the experiment on residual effect of potassium applied in bengalgram are presented in Table15. The data revealed that the bengalgram crop has responded to the residual potassium applied to sunflower. The treatments where different levels of K were added to the preceding crop, the effect was more pronounced. The residual application of K had influenced the growth and yield parameters compared to the farmer s practice. The number of pods per plant, test weight, grain and straw yield differed significantly. The number of pods per plant increased from 34.0 to 49.33, test weight (100 seeds) from 18.8 g to g. The grain and straw yield differed significantly from 1214 kg ha -1 to 1537 kg ha -1 and 944 kg ha -1 to 1172 kg ha -1 due to residual effect of K applied to preceding sunflower crop. However, there was no significant difference in test weight, grain and straw yield between treatments 50, 75 and 100 per cent K application. Rabi : The results of the experiment on residual effect of different levels of potassium to bengalgram in sunflower-bengalgram sequence are presented in Table 15. The data revealed that the treatments where different levels of K added to the preceding crop, the effect was more pronounced. The number of pods per plant, test weight pod yield and straw yield differed significantly. The number of pods per plant increased significantly from 32.0 in the farmer s practice to with RDF, test weight from 16.40g to 23.43g. The grain yield differed significantly from 1092 kg ha -1 in farmer s practice to 1512 kg ha -1 in RDF and the straw yield from 862 kg ha -1 to 1162 kg ha -1 due to residual effect of K application. However, no significant difference in number of pods per plant, test weight, grain and straw yield was observed between treatments with 50, 75 and 100 per cent K application. The pooled data of residual effect of potassium in bengalgram is presented in Table 15. The results revealed that the mean grain yield increased significantly from 1153 kg ha -1 to 1508 kg ha -1 and straw yield from 888 kg ha -1 to 1167 kg ha -1 with application of 100 percent potassium. However, no significant difference in grain and straw yield was observed between the treatments 50, 75 and 100 per cent K application.

69 Table 15. Effect of potassium management practices on growth and yield of rabi bengalgram under vertisols in TBP Command area Treatments Rabi No. of tillers per hill Test Weight (g) Grain yield (kg ha -1 ) Straw yield (kg ha -1 ) Rabi Pooled Rabi Rabi Pooled Rabi Rabi Pooled Rabi Rabi Pooled T 1 - Control T 2 - Farmer s practice T 3 - RD N alone T 4 - RD N and P T 5 - RD NP + 50% K T 6 - RD NP + 75% K T 7 - RD NP + 100% K S. Em± CD at 5% R rabi

70 General view of the Expt. Plot Recommended N alone Recommended N and P Plate 3. General view of the experimental plot of bengalgram crop

71 Farmer s practice Recommended Np + 50% K Plate 3. Contd.. Recommended N, and K