Soil potassium dynamics under intensive rice cropping in TBP command area of north Karnataka

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1 An Asian Journal of Soil Science Volume 8 Issue 2 December, Research Article Soil potassium dynamics under intensive rice cropping in TBP command area of north Karnataka Received : ; Revised : ; Accepted : MEMBERS OF RESEARCH FORUM : Summary Corresponding author : K. NARAYANA RAO, Department of Soil Science and Agricultural Chemistry, University of Agricultural Sciences, RAICHUR Distribution of different forms of potassium was studied in surface and subsurface soils samples of paddypaddy cropping sequence in TBP command area. The water soluble K ranged from 0.04 to 0.18 per cent, and 0.04 to 0.23 per cent, exchangeable K 1.03 to 3.26 per cent and 1.30 to 3.40 per cent, non exchangeable K 4.10 to per cent and 4.11 to per cent and lattice K to per cent and to per cent in surface and subsurface layers of total potassium, respectively. All the forms of soil potassium were correlated with each other indicating the existence of dynamic equilibrium among them. (KARNATAKA) INDIA narayan3228@rediffmail.com Co-authors : N.A. YELEDHALLI AND H.T. CHANNAL, Department of Soil Key words : Correlations, Cropping sequence, Dynamic equilibrium, Forms of potassium, Paddy How to cite this article : Rao, K. Narayana, Yeledhalli, N.A. and Channal, H.T. (2013). Soil potassium dynamics under intensive rice cropping in TBP command area of north Karnataka. Asian J. Soil Sci., 8(2): Science and Agricultural Chemistry, University of Agricultural Sciences, DHARWAD (KARNATAKA) INDIA Introduction The importance of K in Indian agriculture is increasing with the passage of time. The response of crops to K application is frequent and pronounced. The soil potassium gets depleted with the use of high yielding crop varieties, increase in cropping intensity and intensive use of nitrogen and phosphatic fertilizers. 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. Paddy-paddy is the dominant cropping sequnce of the region-2 (North Eastern Dry Zone) of Karnataka which is followed in dominant black soils under irrigated condition. 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 (Anonymous, 2009). Despite enormous growth of this cropping systems in this region, there are reports of stagnation in the productivity of paddy crop with possible decline in production which have raised doubts on sustainability of this cropping system in future. The farmers of the region lacks the proper knowledge of balanced nutrition, assuming that these soils are rich in potassium. They are applying heavy doses of nitrogen (200% more than the recommended), phosphorus as per recommended dose and little (about 25% of recommended dose) application of potassium for paddy under irrigated condition. 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. 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. Potassium, being an essential element for plant growth, exists in four forms in soils viz., water soluble, which is taken up by plant directly, exchangeable K, held by negatively charged on clay particles and available to plants, fixed K, which is trapped between layers of expanding lattice clays and lattice K an integral part of primary K bearing mineral. For practical appraisal of K supplying power of these soils, it is essential to have the knowledge of all four forms of K and their status. Although, the attempts have been made earlier to study potassium status and its dynamics in different soils of Karnataka but, the information on status of potassium and

2 Table A : Details of the soil samples collected for study under paddy-paddy cropping sequence Sr. No. Name of the village Taluk District Soil type Geology Soil Classification Rainfed/ 1. Kasbe camp 2. Vijayanagar camp 3. Kalmala Typic hapluetert 4. Ganjalli Mixed red and black Typic pallustert 5. Devasugur Mixed red and black Typic palluetert 6. Sirwar 7. Harvi 8. Neermanvi 9. Amarewara camp 10. Potnal 11. Jawalgera 12. Raithanagar camp 13. Araginamara camp 14. Gorebal camp 15. Hanchinal camp its dynamics in dominant black soils of the region under paddy-paddy cropping systems is lacking. Resource and Research Methods Seventy five surface and subsurface soil samples of dominant soil series of () were collected from different villages of, and Sindhnur taluks of District and the details of soils collected are presented in Table A. The samples were analyzed for ph, (Jackson 1973), electrical Conductivity, EC (Jackson,1973), particle size distribution (Piper, 1966), organic carbon, O.C. (Jackson 1973), calcium carbonate, CaCO3 (Piper, 1966) and cation excgange capacity, CEC ( 1965). The different forms of potassium like water soluble potassium in 1:2 soil water suspension (MacLean, 1961), exchangeable potassium (Knudsen et al., 1982), non exchangeable potassium by boiling nitric acid extraction method (Knudsen et al., 1982) and total potassium content by digesting the soil samples with hydrofluoric acid (Lim and Jackson, 1982) were determined. The potassium in the extracts was estimated by using flame photometer. The lattice potassium was calculated by deducting the sum of water soluble, exchangeable, non exchangeable from total K. The correlations studies were carriedout with the help of statistical package for social sciences (SPSS) software and the results are discussed accordingly (Table A). Research Findings and Discussion The findings of the present study as well as relevant discussion have been presented under following heads : Forms and distribution of K : The water soluble potassium content of surface and 320 subsurface layers ranged between 4 to 14 and 1 to 10 mg kg-1 respectively and decreased with soil depth. The water soluble K contributed least to the total potassium, i.e to 0.23 per cent in surface and 0.04 to 0.13 per cent in subsurface layers. (Table 1). A similar trend was reported by Kadrekar (1976) and Hebsur (1997). The higher amount of water soluble K in the surface layer could be attributed to more exposure of K bearing minerals to weathering and or upward translocation of K from sub surface layers by capillary rise or due to addition of K through plant residues, manures and fertilizers. 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 (Table 1). Similar results were reported by Patel et al. (1986) and Venkatesh and Sathyanarayana (1994) for medium black calcareous soils of western Gujarat and some black soils of North Karnataka. The per cent contribution of exchangeable K to the total K varied from 1.03 to 3.26 and 1.30 to 3.40 per cent from surface and subsurface layers, respectively. The content of exchangeable K increased with depth. The higher amount of K in the subsurface layer might be due to higher amount of clay content with higher surface area and more adsorption on exchange sites (Table 1). 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 (Table 1). These values are in comparison with the results reported by Venkatesh and Sathyanarayana (1994) for black soils of North Karnataka. 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. The lattice K fraction followed a definite pattern with respect to depth wise distribution of potassium. The content

3 SOIL POTASSIUM DYNAMICS UNDER INTENSIVE RICE CROPPING IN TBP COMMAND AREA OF NORTH KARNATAKA 321

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5 SOIL POTASSIUM DYNAMICS UNDER INTENSIVE RICE CROPPING IN TBP COMMAND AREA OF NORTH KARNATAKA Table 2 : Simple correlation co-efficients between selective soil properties and different K forms of surface soil samples under paddy-paddy cropping sequence Parameters 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) Coarse sand (%) 0.196* * 0.210* Fine sand (%) Silt (%) Clay (%) 0.254* 0.282* 0.463* 0.458* 0.467* OC (g kg-1) CaCO3 (%) 0.421* 0.170* 0.421* 0.478* 0.483* CEC (c mol(p+) kg-1) * 0.411* 0.474* 0.482* Simple correlation co-efficients between different K forms of surface soil samples under Paddy-Paddy cropping sequence WS-K (mg kg-1) Exch-K (mg kg-1) Non Exch-K (mg kg-1) 0.159* 0.448* Lattice-K (g kg-1) 0.316* 0.457* 0.507* Total-K (g kg-1) 0.310* 0.480* n = 150 * and ** indicates significance of value at P=0.05 and 0.01, respectively * 0.999* 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, respectively (Table 1). These values are in accordance with the findings of Pharande and Sonar (1996) for soils of Maharashtra and Venkatesh and Sathyanrayana (1994) for black soils of North Karnataka. 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 and and per cent in surface and subsurface layers of the both the cropping sequence, respectively. The content of lattice K increased with soil depth. The total K content ranged from 3.38 to 10.6 g kg-1 and 3.89 to 11.0 g kg-1 and increased with depth (Table 1). These values are comparable with the values obtained by Raskar and Pharande (1997) for vertisols of Western Maharashtra. The high content of total K in these soils might be attributed to the dominance of K bearing primary minerals such as mica in clay fraction (Ranganathan and Sathynarayana, 1980). The correlation studies indicated that the water soluble K is negatively but non significantly correlated with exchangeable K (Table 2). Similar observation was made by Amiri and Dorudi (1997) in paddy soils of Northern Iran, indicating its non replenishment from other forms of K. Exchangeable K was positively and significantly correlated with non exchangeable K, lattice K and total K indicating dynamic equilibrium among all these forms of K (Table 3). The non exchangeable, lattice and total K is correlated with all the forms of K. The correlation among different forms of K and soil properties indicated that the all the forms of K were positively and significantly correlated with clay but negatively correlated with sand and silt fractions (Table 2). This might be due the dominance of mica in the finer fraction of soils. The 323 observations are in conformity with findings of Singh et al. (1985) and Gali (1998), suggesting that available K status of the soil is largely governed by clay fraction. All the forms of K were positively and significantly correlated with CaCO3 and CEC and negatively with organic carbon (Table 2). It is quite evident that an increase in CEC means increased adsorption of potassium. Patil and Sonar (1993), observed similar correlations of exchangeable K with CEC and CaCO3. Conclusion : The availability of potassium mainly depends on the status and the forms of K present in the soils. Among the forms, the exchangeable and non exchangeable K play a major role in availability of K to plants. Literature Cited Amiri, R. and Dordoi, M.S. (1997). Potassium forms and clay mineralogy of some paddy soils in Northern Iran. J. Pot. Res., 13(1): Anonymous (2009). Statistical Abstract of Karnataka, Directorate of Economics and Statistics, BANGALORE (KARNATAKA) INDIA., C. A. (1965). Methods of soil analysis. Part II Chemical and microbiological properties. American Soc. Agron., Inc. Madison, USA. Hebsur, N.S. (1997). Studies on chemistry of potassium in sugarcane soils of North Karnataka. Ph.D. Thesis, University of Agricultural Sciences, DHARWAD, KARNATAKA (INDIA). Hegde, D.M. and Sudhakar Babu, S.N. (2001). Nutrient mining in agroclimatic zones of Karnataka. Fert. News, 46(7) : Gali, S.K. (1998). Studies on potassium dynamics in rice soils of different agro climatic zones of Karnataka. Ph.D. Thesis, University of Agricultural Sciences, DHARWAD, KARNATAKA (INDIA).

6 Jackson, M.L. (1973). Soil chemical analysis. Prentice Hall (India) Pvt. Ltd., NEW DELHI (INDIA). supplying power of medium black calcareous soils of Western Gujarat. J. Pot. Res., 2 : Kadrekar, S.B. (1976). Soils of Maharashtra State with reference to the forms and behavior of potassium. Bull. Indian Soc. Soil Sci., 10 : Pharande, A.L. and Sonar, K.R. (1996). Depth wise distribution of different forms of potassium in important vertisol soil series of Maharashtra. J. Indian Soc. Soil Sci., 12(2): Knudsen, D. Peterson, G.J., and Pratt, P.F. (1982). Lithium, sodium and potassium. In: Method of soil analysis part II. Chemical and microbiological properties. Ed. Page, A.L., American Society of Agronomy, Inc., Soil Science Society of America. Inc., Madison, Wiscosin, USA. Piper, C.S. (1966). Soil and plant analysis. Hans Publishers Bombay. Lim, C.H. and Jackson, M.L. (1982). Dissolution for total chemical analysis In: Method of soil analysis part II Chemical and microbiological properties. Ed. Page, A.L., American Society of Agronomy, Inc., Soil Sci. Soc. Am. Inc Madison, USA. Raskar, B.N. and Pharande, A.L. (1997). Different forms of potassium and their distribution in some important soil series of Vertisol and Alfisol of western Maharashtra. J. Pot. Res., 13(1): Mac Lean, A.J. (1961). Potassium supplying power of some Canadian soils. Canadian J. Soil Sci., 41 : Singh, Y.P., Singh, M. and Singh, R. (1985). Forms of soil potassium in western part of Haryana. J. Indian Soc. Soil Sci., 33 : Ranganathan, A. and Sathynarayana, T. (1980). Studies on potassium ststus of soils of Karnataka. J. Indian Soc. Soil Sci., 28: Patil, Y.M. and Sonar, K.R. (1993). Dynamics of potassium in swell-shrink soils of Maharastra. J. Pot. Res., 9(4): Venkatesh, M.S. and Sathyanarayana, T. (1994). Status and distribution of potassium in vertisols of North Karnataka. J. Indian Soc. Soil Sci., 42 : Patel, M.S., Patil, R.G. and Sutaria, G.S. (1986). Potassium 8Year of Excellence th 324