Potential of Industrial By-Products in Ameliorating Acid Soils for Sustainable Crop Production

Transcription

1 The Fourth Dr. G.S. Sekhon Memorial Lecture* Potential of Industrial By-Products in Ameliorating Acid Soils for Sustainable Crop Production Dr. D. Jena Professor and Head & President, ISSS, Bhubaneswar Chapter Department of Soil Science & Agricultural Chemistry OUAT, Bhubaneswar dinabandhu_jena@yahoo.co.in Organized by: ISSS, Ranchi Chapter, BAU, Ranchi & ISSS, New Delhi * Delivered on 2 nd September 2013 at Birsa Agricultural University, Kanke, Ranchi and organized by the Ranchi Chapter of the Indian Society of Soil Science.

2 Potential of Industrial By-Products in ameliorating acid soils for sustainable Crop Production I would like to thank the Ranchi Chapter of the Indian Society of Soil Science for giving me the honor and privilege to deliver the 4 th Dr. G.S. Sekhon Memorial Lecture a doyen among soil scientists and whose contributions to soil science are legendry. Dr. Sekhon made commendable contributions towards advancements of different areas of soil science. His pioneering work on potassium based on bench mark soil series of the country, soil testing, environmental pollution leading to optimum use of fertilizers and nutrients will go on a long way in increasing agricultural production in the country with minimal degradation of the environment. Acid soils constitute about 30 % of the total cultivable area in India. These soils are formed due to drastic weathering under hot humid climate and heavy precipitation. Laterization, podozolisation and accumulation of undecomposed organic matter under marshy conditions contribute to the development of soil acidity. Acidic parent materials (granite), leaching of bases from the surface soils due to high rainfall, use of nitrogenous fertilizers like ammonium sulphate, ammonium nitrate, ammonium chloride and urea induces soil acidity. In India, acid soils occur in the Himalayan region, the Eastern and North-eastern plains, peninsular India and coastal plains under varying topography, geology, climate and vegetation. Most of these soils belong to the soil order, Ultisols, Alfisols, Mollisols, Spodosols, Entisols and Inceptisol. The acid soils are mostly distributed in Assam, Manipur, Tripura, Meghalaya, Mizoram, Nagaland, Sikkim, Arunachal Pradesh, West Bengal, Jharkhand, Orissa, Madhya Pradesh, Himachal Pradesh, Jammu & Kashmir, Andhra Pradesh, Karnataka, Kerala, Maharastra and Tamilnadu. It is estimated that about 12 % soils are strongly acidic (ph < 5.0), 48 % moderately acidic (ph ) and 40 % mildly acidic (ph ). In acid soils, the concentration of H + ions exceeds that of OH - ions. For the long time, it has been considered that the soil acidity is owing to exchangeable H + ions only. The dominance of Al in the soil acidity was reported in early thirties. Most of the clay particles interact with H + ions. Hydrogen saturated clay undergoes a spontaneous decomposition. In the octahedral layer, hydrogen ions replace the Al ions. The Al 3+ released is then absorbed by the clay complex and a H-Al-Clay complex is formed rapidly. The trivalent aluminum hydrolyses to monomeric and polymeric hydroxyl-aluminum complexes and contribute to soil acidity. Exchangeable H + and exchangeable Al 3+ in major soil groups of India, comprises 21 and 79 % of exchange acidity, where as ph dependant and exchange acidity accounted for 71 % of the total acidity. The unaccounted for acidity were probably due to hydrolysis of Fe and Mn on the exchange sites of the soil complex. The important soil factors that control the different kinds of soil acidity are ph, organic matter, exchangeable and extractable Al. Crop production constraints in acid soils The upland acid soils have coarse soil texture with high infiltration rate, low water holding capacity, high permeability, soil crust formation, excessive leaching of nutrients and high bulk density. Seed germination is affected by surface soil crust. Application of organic matter, tank slit, conservation tillage, contour and strip cropping, intercropping of cereals with legumes or oilseeds and in-situ rainwater harvesting are some of the suitable methods for improving crop production in such soils. Common problems of acid soils in respect of chemical properties are low ph, low CEC (due to dominance of 1:1 type of clay), low base saturation, high Fe, Al, and Mn, high P fixing capacity, clay fractions consisting of rather low surface active minerals. These problems could be managed by amelioration with liming, which increases soil ph, base status and CEC, inactivates Fe, Al and Mn in soil solution, reduce acidity and P fixation in soil. Acid soils are deficient in calcium. Exchangeable Mg content of such soils is also poor. Sulphur deficiency is common in upland coarse textured soils. Micronutrients such as B and Mo are often deficient in acid soils. Acid soils of India are generally low in organic carbon, available nitrogen and biological activity. 1

3 Acid Soil Management Considering the importance of acid soils in Eastern India, studies on their management were carried out by several workers. These results were well documented in several publications. Management of acid soils should aim at realization of production potential either by addition of amendments or by manipulation of agricultural practices to derive optimum crop yield under acidic conditions. Liming the acid soils, improved its physical, chemical and biological properties. There was significant improvement in yield with increased in availability of several plant nutrients. In addition to liming, the present thinking on acid soil management includes integration of nutrient management practices with in situ soil moisture conservation technology, agro-forestry using a system approach of crop production to meet the food and nutritional security of the dominated tribal population in the rainfed regions of India. No doubt, liming technology is cost effective and can increase the crop yield by two-fold provided the liming materials are available to the farmers at sowing time. Historically, lime and gypsum have been used to correct soil acidity, but their widespread use can be limited by availability and cost especially in many developing countries. Thus, low-input alternative or complementary methods need to be developed. Many industrial byproducts containing calcium and sulphate can act as a alternative amendments. However, their potential to correct soil acidity and their environmental risk need to be evaluated before large-scale use. Liming Source And Efficiency Among the naturally occurring lime sources, calcite, dolomite and stormatolitic lime stones are important. Since calcite and dolomite have industrial use, its application in agriculture is not economical. In India, the total reserve of all categories of lime stone is about 76,446 million tones (mt) out of which 11,562 mt are under proved category, 16,463 mt under probable category and 48,419 mt under possible category. Deposits of about 40 mt of stormatolitic lime stone, a poor grade lime containing % CaO, 12 % MgO and 0.5 % P 2 O 5 is found in Odisha. Its use in acid soils needs detailed study. Several industrial wastes such as paper mill sludge (PMS) from paper mills, basic slag from steel industry, preesmud from sugar mills using carbonate process have been tested successfully in acid soil regions of India as amendments, which are eco-friendly. Liming material must be locally available, properly ground and should have high neutralizing value and low cost for use by small and marginal farmers. Although huge amount of basic slag (100 mt per annum) is generated from steel mills located in Bhilai, Rourkela, Bokaro, Durgapur, Burnpur and Jamshedpur, its use is limited due to high grinding cost. On an average, Indian slag contains 1 to 3 % P 2 O 5, 24 to 50 % CaO and 2 to 10 % MgO. Basic slag Basic slag is a by product of the basic open-hearth method of making steel. Basic slag contains 32 % total calcium and % total phosphorus out of which % is citrate soluble. Its performance compares well with superphosphate in acid soils with leguminous crops. Basic slag increases soil ph and mobile fraction of P, K, Ca and Mg during incubation period. Slag has been reported to increase ph, available P and decrease Al in South Nigeria acid soils. Also slag increased Ca, K uptake, promoted micronutrient uptake and increased dry matter yield. Studies from Brazil revealed that application of calcium silicate slag resulted in significant grain yield increase, tissue silicon content and silicon accumulation in straw and grain. Slag can also reduce soil acidity and increase available P, Si, exchangeable Ca and base saturation. In India, several studies in past indicated that the application of basic slag at 1-1 ½ times the lime requirement of acid soils resulted in higher yield of paddy. In a field experiment with clay-loam soil of ph 5.5 in CRRI, Cuttack, application of basic slag resulted in higher ph and higher total and extractable P. The rice yield was increased by 2.93 q ha -1 with basic slag. In a field trial at Palampur with soil ph 5.2, the yield of rice-wheat cropping system was significantly increased with use of basic slag from Bhilai. The favorable effect of basic slag in acid soils is due to its effect on the microbial population of the soil. This increases the water stable 2

4 aggregates, improves the rate of mineralization and enhances soil fertility. Use of basic slag in agriculture has been suggested as a P-carrier and as amendment for acid soils. The beneficial effect of basic slag on maize, wheat, gram and groundnut in Bihar has been well documented. Tata Steel Industry, Jamshedpur generated about 6 lakh tonnes of basic slag annually and that could be used in acid soils. Basic slag contains heavy metals (Cd, Cr, Ni). High amount of Fe and Al present in red and laterite soils bind these toxic heavy metals tightly and thus prevent them to remain in available form in soil and plant. There is hardly any possibility of contamination of underground aquifers through percolation. Results of field experiments with soil ph in Jharkhand revealed that percent yield increase with basic 4 q ha -1 over farmer s practice was from 11.2 to 23.8 in wheat, from 8.15 to 42.5 in gram, from 5.9 to 8.1 in mustard and 6.42 to 8.56 in rai. Phosphogypsum (PG) Gypsum (CaSO 4.2H 2 O) is mined from natural deposits or as an industrial by-product (phoshogypsum) from the manufacture of phosphoric acid plant or high analysis super phosphate fertilizer plant. The principal chemical reaction involved is presented by ; Ca 10 F 2 (PO 4 ) + 10 H 2 SO H 2 O D 10 CaSO H 2 O + 2 HF + 6 H 3 PO 4 (Fluorapatite) (gypsum) Ca 10 F 2 (PO 4 ) + 7 H 2 SO H 2 O D 3 Ca (H 2 PO 4 ).H 2 O + 7 CaSO HF (Fluorapatite) (Monocalcium phosphate Monohydrate) Researchers in southeastern United States, Brazil and South Africa have found that gypsum does not increase soil ph, but can ameliorate aluminum toxicity in improving root growth and crop yield. In limed soil, the ph is raised, thus increasing the ph-dependant charges on soil colloid, which in turn retain the released Ca 2+, preventing its downward leaching. Gyspum, being a neutral salt, dose not increase CEC. On dissolution, the SO 4 2- ion leached down along with Ca 2+. The Ca 2+ ions replace Al 3+ ions from exchange site and the released aluminum react directly, or indirectly with sulphate ion to form AlSO 4 - ions which are non-phytotoxic. Another probable mechanism of aluminum detoxification is the formation of-insoluble Al(OH) 3 through following reactions : Fe, Al Oxyhydroxides - OH + Ca SO 4 " - OH Fe, Al Oxyhydroxides = SO 4 + Ca OH - 3 Ca (OH) Al 3+ " 2 Al (OH) Ca 2+ (Insoluble) Deficiency of Ca or toxicity of Al are the major limiting factors for crop growth in acid soils. Liming the top soil has little effect on alleviation of sub-soil acidity. On the other hand, application of gypsum to top soil has been found to increase exchangeable Ca and decrease exchangeable Al in sub soil. The beneficial effect of surface application of PG in highly eroded sloppy land maintained infiltration, reduce run off and prevent soil loss. Phosphogypsum contains 16 % S and % Ca. It also contains about 0.2 to 1.2 % phosphorus. In Odisha, about 10 million tones of phoshogypsum is dumped around fertilizer industry at Paradip and is an efficient source for correcting S deficiency in crops. Addition of 60 kg S ha -1 to acid soil of Bhubaneswar reduced the exchange acidity, exch. Al 3+ and exch. H +. 3

5 Paper mill sludge (PMS) Paper mill sludge is a by-product of paper mill. It is estimated that about 2 lakh metric tones of PMS with % neutralizing value and 22 to 35 % Ca content are dumped around four paper mills located in Cuttack, Rayagada, Brajarajnagar and Jeypore of Odisha. Efficiency of PMS was studied to find out the optimum dose of lime in reducing the soil acidity by neutralizing exchangeable Al 3+. With increase in levels of lime, there was significant rise in soil ph with decrease in exchange acidity, exchangeable H + and Al 3+. Application of 0.2 LR was adequate to bring the ph to a safe level for profitable crop production with neutralization of total exchangeable Al 3+ within first week of application. The research results of OUAT, Bhubaneswar revealed that application of 0.2 LR raised the ph from 5.1 to 6.9 and decreased the exchangeable Al 3+ from 0.62 to zero cmol (p + ) kg -1 within seven days of incubation. Pressmud (PM) Pressmud is a by-product of sugar industry and can be utilized as an amendment to improve soil physical properties. Efforts were made at OUAT, Bhubaneswar to characterize pressmud as a liming material for acid soils. The ph of the pressmud varied between 6.5 to 6.92 and OC 16-18%. The neutralizing value of 22-24% indicated that it cannot be compared with CaCO 3 or PMS as a liming material. However, it can be used as an acid soil amendment because of high organic carbon content. The results of an incubation study with an acidic upland soil of Bhubaneswar (ph-4.8, exch. acidity-0.6 cmol (P + ) kg -1 ) showed that the ph increased significantly at all levels (0.2, 0.3, 0.4 LR) of PMS or PM. The exchange acidity decreased in all the lime treated soils and attained a value of zero on 7 th day of incubation. The study also indicated that application of 0.2 LR or 0.3 LR was adequate to neutralize exchangeable Al +3. A Field study was conducted for three seasons on groundnut in an acidic upland site of OUAT Central Farm having ph 4.5, exchange acidity : 0.96 Cmol (p + ) kg -1 ; O.C: 3.4 g kg -1 and LR: 6.3 t CaCO 3 ha -1. PMS and PM was applied alone or in combination of 75:25, 50:50 and 25:75. Application of PMS, PM and their 0.2 LR increased the soil ph from 4.5 to The peak ph was attained at 25 days of lime application and remained above 5.0 during the entire growth period. Exch. Al 3+ decreased rapidly within 14 days of lime application and there after slowly, finally, it attained a negligible value between days of application. Among the lime sources, the decrease in exchange acidity in PMS (100 %) was higher as compared to PM (100%). The pod yield in lime control was q ha -1 and increased by % in lime treatments. Highest yield of 36.4 q ha -1 was obtained when PMS and PM was applied in ratio of 75:25. Stromatolyte Deposits of about 40 million tones of stromatolyte is reported in Koraput districts of Odisha. It is a low grade lime stone commercially not exploited by steel industry. Attempt was made to evaluate its suitability as liming material. The rock was collected from Gupteswar area of Koraput district, ground to pass through different mesh sieves, viz. 22, 60, 100, 350. The neutralizing value of rock fragments was about 80 %. The fineness of soil particles had no effect on neutralizing value of the rock fragments. On an average, the Calcium content of rock fragment was about 17.3% and Mg content 10.5 %. The efficiency of stromatolyte was compared with PMS or calcite through several studies carried out in OUAT, Bhubaneswar. In a pot culture experiment with maize, the ph was increased from 4.47 to 5.85 after 7 days of application of stromatolyte. Soil amelioration with CaCO 3 and PMS proved better during early stages of maize crop growth (28 th day) as compared to stromatolyte sources. Thereafter, the rock resources maintained higher ph than PMS and CaCO 3. The stromatolyte of different size particles had almost similar influence on reducing the exchange acidity, Al 3+ and H +. 4

6 The maize biomass yield was increased by complexing and ameliorating the acidity, raising the ph to higher levels. Raw form of stromatolyte of 22 mesh sieve was more effective as compared to standard PMS or CaCO 3. LD slag Linz-Donawitz (LD) slag, containing 29 % Ca, 21 % Fe and 5 % Mg, is a by-product of the iron and steel-making industry. The low P content of the LD slag discouraged its use in agriculture as a phosphatic fertilizer, but the total high Ca and Mg contents makes the LD slag a potential liming agent. Experiments in several European countries have demonstrated the ability of LD slag to raise the ph of acid soils, increasing the Ca and Mg contents of the soils exchange complex. Application of LD 1.6 t ha -1 to soils with ph of 4-5 modified the physical and chemical properties of the soil and increased the dry matte yield by %. Several studies were conducted in OUAT, Bhubaneswar with LD slag from SAIL, Rourkela having ph 10.49, Ca content %, Mg content 2.13 % and neutralizing value 58.8 %. Application of LR to Alfisol with ph-4.53, exchange acidity 0.39 cmol (p + ) kg -1 and exchangeable Al cmol (p + ) kg -1 increased the ph to There was little difference in soil ph when LD slag was applied at sowing or at 5 and 10 days before sowing. Application of LD 0.3 LR recorded higher ph as compared to 0.1 or 0.2 LR. About 75% of exch. Al 3+ was neutralized within 14 days of LD Slag application. Application of LD 0.3 LR at 10 days before sowing resulted in highest ground nut pod yield of 31.8 q ha -1 as against 20.6 q ha -1 in control. In another field study, the efficiency of LD slag was compared with PMS as sole or in combinations. Sole application of LD slag was inferior to PMS. However, combined application of LD slag and PMS (1:1 0.3 LR increased the pod yield by 58 to 90 %. Crop response to lime and fertilizers Lime requirement of acid soils of India varied from 2.6 to 24.0 t CaCO 3 ha -1 and was closely related to soil ph and organic matter content. But, full LR dose is often not economical. For laterite soils of Bhubaneswar, application of CaCO 0.5 LR was enough for maize, although exchangeable Al was neutralized with 0.25 LR. Application of % of LR in furrows increased the yield of green gram, groundnut, black gram, soybean, lentil, pea and gram over no lime control. Experiments on direct and residual effect of liming in different cropping system conducted in sandy loam soil at G. Udayagiri in Odisha showed that, grain yield of mustard, wheat and cowpea increased by 41, 28 and 21 %, respectively due to direct effect of 0.25 LR and maize yield increased by 7-13 % under residual condition. Organic amendments also reduce exchangeable Al in soils due to precipitation of Al ions by OH ions released from organic ligands. Several workers have suggested for application of organic amendments (FYM) either alone or in combination with lime for neutralizing soil acidity as well as nutrient availability. Liming also stimulates microbial activity leading to mineralization of organic N and fixation of N 2. Research results from BAU, Ranchi indicated that application of 2-4 q ha -1 increased the yield of rape seed, mustard, wheat, green gram, maize, pigeon pea, field pea, black gram, groundnut by 14 to 52 % over farmer s practice. Results of ICAR Network Project on Acid soils revealed that application of lime 2-3 q ha -1 in acid soils improved the yields of wheat, maize, rape seed, green gram, black gram, groundnut, mustard, pigeon pea and pea by % in states like Himachal Pradesh, Assam, Kerala, Maharastra, Meghalaya, Jharkhand and Odisha. Application of half the recommended dose of fertilizers with lime was at par or superior to the full RDF without lime in acid soils. Economic benefits in crops with lime application in acid soils ranged from Rs. 2-6 per rupee investment. Some promising crop varieties for pulses and oilseeds grown in acid soils were identified which are relatively tolerant to soil acidity. Field experiments conducted in several districts of Odisha with varying ph using 0.2 LR applied in furrows below the seeds at the time of sowing showed that, liming alone increased ground nut yield by 5

7 17-36 % over farmer s practice (FP) in the red soils of Mayurbhanja, Ganjam and Nayagarh. The yield of green gram increased by 5-21 % over FP in laterite soils of Khurda and Dhenkanal. Cabbage and cauliflower responded significantly to lime application in Koraput and Kandhmal districts and response varied between % over FP. Management of iron toxic soils Iron toxicity occurs in hill bottom red and lateritic soils (Alfisol, oxisol, ultisol) under undulating topography and impeded drainage condition. These soils are characterized by poor base saturation and poor supply of available nutrients like K, Ca, Mg, P, Zn and Cu. Iron toxicity symptoms in rice is seen as bronzing, when Fe 2+ concentration in soil solution goes up to mg kg -1 due to reduced conditions under prolonged submergence. The concentration of Fe 2+ further increases due to lateral flow of Fe from an adjacent upland to low land rice fields during rainy season. In most of the rice soils, the concentration of Fe 2+ increases upon flooding and attains peaks after 2-5 weeks. In iron toxic soils, substantial amount of iron is oxidized and get deposited on the active roots making physical barrier for absorption of plant nutrients from soil solution. Under extreme conditions, more number of roots become blackish in colour and only a few remain whitish to brownish in colour. Plants get stressed and are forced to produce more new roots at the expense of shoot growth. Production and decay of roots continue throughout the plant growth period. Iron toxicity in plants promotes sterility and the grain yield is reduced by 20-80% depending upon the situation. Iron toxicity can be corrected by providing intermittent drainage. It reduces uptake of iron, manganese and increases availability of other plant nutrients. Liming of 1-2 t ha -1 along with K application had beneficial effect on alleviating Fe toxicity in rice by 27% over lime control in soils of Odisha. Application of 0.5 LR or 40 kg ha -1 or 10 kg ha -1 increased the grain yield by 8.25, and q ha -1, respectively over control. Foliar application of MnSO 0.6% had no beneficial effect on rice in iron toxic soil. Balanced fertilization helps in alleviating iron toxicity in rice. Application of 90 kg P 2 O 5 ha -1 to iron toxic soil at Barapani farm of Meghalaya resulted in reduction of Fe 2+ from 3.60 to 1.63 mg kg -1. Dipping rice seedling in boronated SSP and FYM slurry before transplanting, helped to increase rice yield by reducing Fe toxicity. In Odisha, about 1 lakh hectare of medium-low land rice suffers due to iron toxicity resulting in yield loss to the extent of 60 to 80 %. Several rice genotypes were evaluated in iron toxic laterite soils of Bhubaneswar for three consecutive years. Rice genotypes like Kalinga III, Udayagiri, Panidhan and Tulasi are tolerant to iron toxicity while, IR 36, Konark, Birupa, Gajapati, Samalai and Indrabati are moderately tolerant to iron toxicity. Genotypic difference in the degree of susceptibility to excess Fe was confirmed by changes in the content of metabolically active Fe 2+, chlorophyll and enzymatic activity in plant parts. Metabolically-active Fe 2+ contents in the leaves, stems and roots of tolerant genotype (ASD-16) was 212, 392 and 4674 ppm as compared to highly susceptible rice genotype (ADT-36) having 281, 442 and 5933 ppm Fe content, respectively. Genotypic differences in degree of susceptibility to excess Fe were attributed to leaf tissue tolerance of high level of Fe, reduced translocation from root to shoot and ability of roots to resist its entry inside the plant. Phosphorus management in acid soils North-Carolina rock phosphate of 35 mesh was reported to be superior to 100 mesh size of Indian phosphate rocks such as Udaipur, Musoorie, Hirapur, Kasipatnam, Maton and Purulia. Udaipur rock phosphate containing dolomite and calcite was found beneficial for maize-mustard cropping system in Alfisols of Odisha. The effectiveness of low reactivity phosphate rock can be increased by applying it to green manure crop preceding the main crop or by inoculation of the field with either phosphate solubilizing micro-organisms or mycorrhiza. Rice grown in iron toxic soils is benefited from application of Udaipur rock phosphate. Several workers have successfully attempted to reduce the cost of P fertilization in acid soils by direct use of rock phosphates to soil having ph < 5.5 or use of rock phosphates and single super phosphate mixture in 1:1 ratio to mild acidic soil (ph ) or to apply rock phosphates to green manure crops prior to rice crops taken in sequence or use of compacted products of Jhamarkotra rock phosphates (JPR). 6

8 Further, it has been recommended to apply the entire P requirement of the cropping sequence, particularly for groundnut-rice cropping system in form of rock phosphates to the groundnut crop grown during rabi season and the residual effect be realized in rice crop during kharif season. This is because the rock phosphate applied to dry season groundnut gets solubilized to greater extent and the portion that gets fixed during dry season becomes available to rice crop due to waterlogged conditions. Use of Fly ash in Agriculture Fly ash is a heterogeneous mixture of amorphous and crystalline material and is generally considered to be a ferrro-aluminosilicate element. In India, about 160 million tones of fly ash is generated annually out of which only 38 % are being used in several sectors like brick making, filling low lands, canal lining and cement manufacturing. Indian fly ash has been found beneficial for the growth of plants due to presence of several plant nutrients. In general, fly ash has low bulk density of g cm -3 and specific gravity of g cm -3. Particle density varies from 2.7 to 3.4 g cm -3, while the moisture retention ranges from 6.1 % at 15 bar to at ⅓ bar. The major components in fly ash are Al, Fe and Si, with smaller concentration of Ca, K, Na, Ti and S. Fly ash contains essential macronutrients including P, K, Ca, Mg and S and micronutrients like Fe, Mn, Zn, Cu, B and Mo. Some are rich in heavy metals such as Cd and Ni. Many trace elements including As, Se and Sr in fly ash are concentrated in the smaller ash particle. In fact, fly ash consists of practically all the elements present in soil except organic carbon and nitrogen. The results of several experiments revealed that application of unweathered fly ash particularly to sandy soil greatly inhibited the microbial respiration, enzymatic activity and soil N-cycling processes like nitrification and N-mineralization. The application of lignite fly ash reduced the growth of several soil borne pathogenic micro-organisms, where as the population of Rhizobium sp. and P-solublizing bacteria were increased in the soil amended with either FYM or fly ash individually or in combination. Several researchers summarized the results of fly ash experiments in India and reported that the yield of wheat, rice, maize and mustard was increased by 6-18 % with tones fly ash per hectare in alluvial soil. Addition of fly t ha -1 in black soil increased the yield of cotton, sorghum, gram, soybean, groundnut and wheat by %. Yield of sunflower and groundnut in red soil with tones FA ha -1 was increased by %. The results of the studies in OUAT, Bhubaneswar indicated that application of 12 t ha -1 increased the soil ph, available P, K, Ca, Mg, S and Zn content in incubated soil where as the content of DTPA Fe, Mn and Cu was decreased. In pot culture experiment, application of 12 t ha -1 increased the yield of cabbage by 10.4 % and maize cob yield by 18 %. Integrated use of FA + lime + pressmud + vermicompost further increased the cabbage and maize cob yield by 17 and 36 %, respectively. No toxic effect of Pb and Cd on cabbage and maize grain were recorded whereas chromium content was above the toxic limit. One time application of 40 t ha -1 to red soil of Bhubaneswar resulted in 24 % higher yield of groundnut during first season and 7-48 % in subsequent years. The rice yield increased by % in alluvial soil and 4 to 18 % in iron toxic soils over 3 years. Accumulation of K, Ca and Zn in rice grain and groundnut kernel was increased in fly ash treatments, but there was reduction in Fe and Mn content. Epilogue The physical constraints of acid soils are high percolation rate, loss of water and nutrients, low water holding capacity and soil crusting. Use of organic manure increases water holding capacity and organic carbon status of soil. Utilization of sub surface water by growing deep rooted crops like groundnut, black gram, green gram, arhar etc. will benefit the farmers. Use of lime for amending crusting soils for different crops like cotton soybean, cowpea, finger millet etc. will be helpful. Naturally occurring sources like calcite, dolomite, industrial wastes like paper mill sludge (paper industry), pressmud (sugar industry), basic slag (steel industry), spent wash etc. can be used as liming material. 7

9 A small dose of % of LR to each crop instead of one time application of full dose give better results. Furrow application of lime is economical. For crops sown in line, method of application is placement. How to do this, when the farmers follow the broadcast method of sowing crops? Vegetable crops respond to lime. However, method of lime application in vegetables has not been standardized. Dose, method and time of lime application for vegetable crops as well as spices especially turmeric and ginger, tuber crops need to be studied. In hill slope and hill bottom soils, agro-forestry and horticultural crops can be grown successfully with lime application. However, the dose, time and method of lime application for these systems need detailed study. Efficiency of liming material can be increased by the use of organics like compost, vermicompost, bio-fertilizers and secondary and micronutrients like sulphur, boron or zinc as per soil tests. For this, laboratory incubation studies need to be conducted. Long term effect of doses of lime with or without organic manure on major crop sequences should be studied. Lime induced immobilization of heavy metals in soils, bio-solids and mine tailings and reduce their availability to crops. Hence, research is needed to develop methods to quantify limeenriched mobilization of deficient plant nutrients and lime induced immobilization of heavy metals in soils. In acid soils of Odisha, the deficiency of micro- and secondary nutrients is emerging as yield limiting factors and is threatening the sustainability of major crop production systems. Hence, regular monitoring of changes in the nutrient status of soil is essential to formulate and adopt suitable remedial measures. Industrial wastes, which have been identified as lime source should be utilized locally as far as possible. Economic distances of transport of such material may be worked out. Steel mill slag and blast furnace slag being slow acting and its production cost being high due to grinding, needs further research for promotion. Utility of Phosphogypsum, a byproduct of phosphate industry though not used to ameliorate surface soil acidity, may counter the aluminum toxicity of sub-surface soil acidity. This requires study. Crop species tolerant to soil acidity need be identified beyond what has already been known. Screening of acid tolerant genotypes of oilseeds, vegetables grown in rainfed/irrigated areas should find a place in acid soil management. The yield of pulses grown in large acid soil areas after kharif rice is very low. Research is needed to find suitable acid tolerant varieties of pulses through varietal screening and management practices for growing them under rice-fallow area. Iron toxic soil can be effectively managed through varietal screening and amelioration measures. Use of Udaipur rock phosphate as a source of Ca and P in acid soil has been worked out and found suitable. It has been used extensively in Kerela because the Kerela Govt. has subsidized the transport cost. Similar initiatives should be taken by other Govts. to use it in acid soil regions of Odisha, Assam, Chhatisgarh, Jharkhand and West Bengal. To reduce fixation and increase availability of applied phosphate instead of water soluble sources of P, insoluble P sources like ground rock phosphate in soils of ph less than 5.5 and 1:1 mixture (on P Basis) of rock phosphate and single super phosphate in soils of ph 5.6 to 6.5 can be preferably used. Management of biological properties of soil can be done through identification of efficient strains of indigenous Rhizobium for biological nitrogen fixation. Studies on effect of lime, P and Mo on the activity of above organisms, rhizospere studies, organic acid release pattern for effective nutrient acquisition and synchronization, soil biotechnology, microbial diversity and, lime v/s biofertilizer interaction are necessary. The dose of well decomposed organic residues to be used for slightly acidic soils should be worked out through multilocational trials, since such organic amendments help to minimize the leaching loss of basic cations by improving physical conditions. Residue incorporation, minimum tillage, conservation agricultural practices need to be promoted in acid soil regions for higher crop productivity. Farmer - Scientist participatory field demonstrations should be carried out in farmers fields in larger areas to popularize the liming technology. Farmers should be trained on the use of lime, source, dose, method of lime application, selection of crop etc. through training. Govt. Extension functionaries, KVKs, ATMAs and NGOs should work in a integrated manner to create awareness among farmers for management of acid soils for sustainable crop production. 8

10

11