INTRODUCTION Fly ash has a potential in agriculture and related applications. Physically Fly Ash occurs as very fine particles, having an average diameter of
INTRODUCTION Fly ash has a potential in agriculture and related applications. Physically Fly Ash occurs as very fine particles, having an average diameter of 25>
It was generally observed that both sandy and clayey soils tend to become loamy in texture (Capp 1978) in the U.S. the average silt content in fly ash is about 63.2% (Sharma et. al. 1989) but in India this content ranges from about 16% (IIT, Kharagpur) to 45% (UAS, Raichur).
Modification of bulk density The grain size distribution especially the silt size range of fly ash affects the bulk density of soil. Chang et. al. (1977) observed that among five soil types Reyes silty clay showed increase in bulk density from 0.89 to 1.01 when the corresponding rates of Fly Ash amendment increased from 0 to 100%. But soils with bulk densities varying between 1.25 and 1.60, a marked decrease in bulk density was observed by the addition of Fly Ash. Page et. al (1979, 1980) reported that Fly Ash amendment to a variety of agricultural soils tend to decrease the bulk density. Optimum bulk density in turn improves the soil porosity, the workability of the soil, the root penetration and the moisture retention capacity of the soil.
Water holding capacity of soil The application of Fly Ash has been found to increase the available water content of loamy sand soil by 120% and of a sandy soil by 67% (PAU, Ludhiana). RRL Bhopal reported that application of Fly Ash increase the porosity of Black Cotton Soil and decreases the porosity of sandy soils and thereby saves irrigation water around by 26% and 30% respectively. Chang et. al. (1977) reported that at an addition of 8% by weight Fly Ash, increased the water holding capacity of soil. They also reported that soil hydraulic conductivity improved at lower rates of Fly Ash application but deteriorated when the rate of Fly Ash amendment exceeded 20% in calcareous soils and 10% in acidic soils. This improvement in water holding capacity is beneficial to the plants especially under rainfed agriculture.
Soil pH In India most of the Fly Ash produced is alkaline in nature. Hence an application of these to agricultural soil increases the soil pH. This property of fly ash can be exploited to neutralize acidic soils (Elseewi et. al. 1978; Phung et. al. 1978). Jastrow et. al. (1979) reported that while addition of fly ash improves soil pH on one hand, it simultaneously adds essential plant nutrients to the soil on the other hand. Page et. al. (1979) observed that experiments with calcareous and acidic soils revealed that fly ash addition increased the pH of the former from 8.0 to 10.8 and that of the latter from 5.4 to 9.9. It has also been reported that the use of excessive quantities of fly ash to alter pH can cause increase in soil salinity especially with unweathered Fly Ash (Sharma et. al. 1989).
Some fly ashes are acidic which may be used for reclamation of alkaline soils. In one of the project sites of FAM at Phulpur, IFFCO has done some work on the reclamation of alkaline soils and observed that the pH of these soils could be brought to near neutral status using these acidic fly ashes.
Effect on soil crust
Fly ash application helps in reducing surface encrustation, which is a problem in red soils (CAS, Raichur). This effect in turn can enhance soil aeration and help in improvement of germination of plants grown on it.
Effect on growth and yield of crops
The positive impact of Fly Ash application on growth & yield of crops has been reported by various agencies. Some of which are given below: Regional Research Laboratory (RRL) Bhopal reported that on an average in comparison to control around 50-60% more yield of Brinjal, around 45% more yield of potato & pea, around 40% more yield of tomato and around 29% more yield of cabbage were recorded in Fly Ash treated plot when Fly Ash was applied @25% of soil. Punjab Agriculture University (PAU) observed that application of Fly Ash @10t/ha increased the yield of wheat from 21.5 q/ha to 24.1 q/ha and that of cotton from 1245 kg/ha to 1443 kg/ha. They have also been found that Fly Ash application @10% by weight increased the dry matter yield of moong from 3.80 gm to 7.36 gm and Fly ash addition from 0 to 80 t/ha increased the yield of paddy from 61.82 q/ha to 63.58 q/ha. College of Agriculture, Raichur observed that the yield of groundnut was increased from 24.1 q/ha to 31.9 q/ha with the application of fly ash @20 t/ha.
View of Groundnut Crop grown on fly ash treated soil at IIT-Kharagpur Forestry and Floriculture species on an Ash Pond (By TERI at BTPS Badarpur) Promising indications were obtained from the preliminary research findings (highlights of which have been given above). A need was felt for collection of a set of empirical data through scientifically designed trials using standard procedures and protocols in a coordinated manner at the national level on the benefits and possible adverse effect of fly ash application in agricultural fields. Fly Ash Mission (FAM) along with its associate agencies has taken up a large number of demonstrative trials (more than 50) at various sites at dispersed locations across the country under varied agro-climatic conditions on a spread of crops, forestry & horticulture species. These trials are being done with varied dose ranges based on the results of the part research experiences of respective centers at their sites. Even upto 100% ash bodies have been used to obtain the extreme effects. The tables 2 & 3, would provide a picture of the locations, plant types and soil types and fly ash dose ranges which have been covered under Fly Ash Mission projects.
Table 2: Field crops & vegetables projects undertaken by FAM S. No.SoilFly ash doses rangeCrops & No. of SitesLocationExecuted by 1Alluvial Soil0-200 t/haRice, wheat (2)Farakka CFRI, Dhanbad 2Alluvial Soil0-100 t/haMustard, jute (1)Farakka CFRI, Dhanbad 3Laterite Soil0-200 t/haRice (5), wheat (4)Bakreshwar CFRI, Dhanbad 4Laterite Soil0-100 t/haMustard, Potato, Lentil (1)Bakreshwar CFRI, Dhanbad 5Black Soil0-50 t/haSugarcaneChidambaramAnnamalai University 6Laterite Soil0-150 t/haGroundnutNeyveliAnnamalai University 7Laterite Soil0-100 t/haSugarcaneNeyveliAnnamalai University 8Black Soil0-150 t/haRice-Green Gram (1)SathamangalamAnnamalai University 9Black Soil0-120 t/haCotton-Rice (1)VellampudugaiAnnamalai University 10Lateritic Soil0-10 t/haRice-Groundnut (3)Kharagpur IIT-Kharagpur 11Lateritic Soil0-20 t/haRice, Groundnut-Mustard (1)KharagpurIIT-Kharagpur 12Lateritic Soil0-30 t/haMustard-Rice (1)KharagpurIIT-Kharagpur 13Lateritic Soil0-10 t/haRice (2)-Mustard, Groundnut, Potato (1)Balarampur, Gholghoria, BurariIIT-Kharagpur 14Lateritic Soil (Red)0-80 t/haSunflower-Groundnut (2)Raichur CAS, Raichur 15Black Soil0-80 t/haSunflower-Maize (2)Raichur CAS, Raichur 16Alluvial Soil0-650 t/haTomato (1), Cabbage (1), Potato (1), wheat (2), Pea (1)- Maize(6), Wheat-Maize (2)Dhodhar, Nilgiri, Rihand NagarRRL, Bhopal 17Alluvial Soil0-650 t/haSunflower (1), tomato (1), Potato (1), Wheat (1), Berseem (1), Red Gram (1), Maize (4), Rice (1)Nilgiri, Rihand NagarRRL, Bhopal 18Alluvial Soil0-40/0-80 t/haRice-Wheat (1), Cotton-Wheat (1), Sunflower-Maize (1), Wheat-Rice (1)Ropar, BhatindaPAU Ludhaina 19Alluvial Soil0-12 t/haWheatRopar (Astalpur)PAU Ludhaina 20Alluvial Soil100% ash body with 7.5 cm soil coverArhar-Wheat (1)BhatindaPAU Ludhaina 21Black Soil0-640 t/ha (Residual Effect)Wheat-Maize, Soyabean-Maize, Lemon Grass (1)SarniRRL, Bhopal 22Alluvial Soil0-640 t/haMaize-Onion, Rice-Sunflower (1)AngulRRL, Bhopal Table 3: Forestry, Land Reclamation projects undertaken by FAM S. No.Soil/Land TypeFly ash doses rangeTree Species & No. of Sites LocationExecuted by 1Laterite Soil0-240 t/haEucalyptus (1)Chaudwar, CuttakTCRDC, Patiala 2Laterite Soil0-24% of pit volume Eucalyptus, Acacia auriculiformis, Casurina equisetifolia, Acacia mangium (1)Durga Prasad, CuttackTCRDC, Patiala 3Alkali-Saline Eroded land ( in Arid Zone)0-20% v/wEucalyptus, Zizyphus, Jojoba (1)JaipurTERI, New Delhi 4Ash Pond-Melia azadirach, Delbergia Sisso, Eucalyptus sp., Populus deltoides(1)BadarpurTERI, New Delhi 5Low Fertile Soil1/3 Pit volumeCeiba pentandra, Melia azadirach, Cassia siamea, Erythrina indica, Cassia glauca, Bauhinia purpurea, Putranjiva ,Pongamia glabra ,Thevetia elifera (1)New Delhi TERI, New Delhi 6Usar 0-5%Rice, Wheat (1)DailapurIFFCO, Phulpur 7Usar 0-5%Rice ,mustard (1)TardihIFFCO, Phulpur 8Usar 0-5%Rice, Wheat (1)YakubpurIFFCO, Phulpur 9Usar 0-6%Rice, Wheat (1)PurisudiIFFCO, Phulpur 10Usar 0-6%Rice, Wheat (1)ParasinpurIFFCO, Phulpur 11Usar 0-6%Rice, Wheat (1)MobarukpurIFFCO, Phulpur 12Ash Pond-Rajnigandha ,Tagetus, Carnation, Palmarosa, Sunflower (1)Badarpur, New DelhiTERI, New Delhi Flyash for reclaiming saline alkaline soil – Rice Crop at IFFCI, Phulpur Flower at Ash Pond (by TERI at Badarpur) These trials have been scientifically designed to collect empirical data on effect of fly ash application on soil, plant and natural ground water near the application site. Indicative monitoring is being done of the soil, plant produce, macro & micro nutrient status including the trace & heavy metal status and also the changes in the natural radioactivity level (if any as a result of application of fly ash) on soil, plant and natural ground water near the trial site. The aspect of the nutritional quality of produce grown in fly ash treated soils if also being addressed in a special project by the National Institute of Nutrition. Institute of Physics, Bhubaneswar is testing the samples of all FAM project sites for some heavy metals and radionucleide levels. More than 1000 samples have been tested so far. At most places the levels appear to be in the normal range. Highlights of the some the important findings from these trials are as follows: Effect on crop growth and yield:
In rice-groundnut cropping system, application of Fly ash @ 10 t/ha to both the crops increased grain yield of rice on an average by 14% and pod yield of groundnut by 26% over control (IIT-Kharagpur)
Application of Fly Ash @ 10 t/ha in combination with organic and inorganic sources either in one or both the seasons in rice-groundnut cropping system increased grain yield or rice and pod yield of groundnut significantly over application of only chemical fertilizer to both the crops (IIT-Kharagpur)
The treatment combination fly ash @ 10 t/ha alongwith Paper Factory Sludge (@ 15 t/ha) & chemical fertilizer (CF) applied to rice and only CF to potato increased grain yield of Rice and tuber yield of Potato significantly over CF applied to both crops in Rice-Potato cropping system. (IIT-Kharagpur)
In Rice – Mustard cropping system, application of Pond ash @ 10 t/ha in combination with organic and inorganic sources to rice and subsequent mustard with CF alone increased yield of rice by 13-15 % and seed yield by 15-18% as compared to the treatment of similar combination but without Pond Ash.(IIT-Kharagpur)
Use of Pond ash/Fly ash either in splits or as one time application along with organic and inorganic sources were equally effective in increasing grain yield of rice and seed yield of mustard, as compared to the treatment without Pond ash / Fly ash. (IIT-Kharagpur)
At College Of Agriculture -Raichur yield of Sunflower was increased by about 25% in red soil under rained as well as irrigated conditions when fly ash was applied @ 60T/ha along with 20t/ha FYM.
More than 70% increase in yield of groundnut was observed when fly ash was applied @ 30 t/ha along with FYM @ 20 t/ha at CAS Raichur.
The yield of maize also increased by about 35% of present when Fly Ash was applied @ 30 t/ha along with FYM @ 20 t/ha (CAS Raichur).
The performance efficiency of both dry fly ash and pond ash in respect of crop growth parameters (yield & improvement in physical and chemical properties of soil was found to be similar by CFRI, Dhanbad in their studies at Farakka & Bakeraswar). Best grain & straw yield of both paddy and wheat crops were observed 200 t/ha pond ash dose (20-40% increases were observed).
Paddy & Wheat crops grown with Fly Ash showed early maturing tendencies at Farakka
Annamalai University, in their trials found that the application of 100 t/ha of Lignite Fly Ash (LFA) did not adversely affect the germination of seeds of Rice, Green-gram, Groundnut, Sugarcane or Cotton. Satisfactory levels of germination were observed and these were found to be at par with those in control plots (where no Fly Ash/ Pond Ash was applied).
Annamalai University also reported yield increases due to LFA application in eight out of twelve of the field trials (with LFA application between 4-120 t/ha) showing a range of 8% to 36% increase in yield of produce (over control).
Significant yields increases were seen in 2nd and 3rd crop of Groundnut at 10t/ha LFA. Increasing the dose of LFA to 100 t/ha significantly increased pod yield in the first crop itself. (Annamalai University).
Effect on soil health:
In rice based cropping system, application of Fly ash/ Pond Ash @ 10 t/ha alongwith organic and inorganic sources wither in one season or in consecutive seasons improved physical properties of soil through decreasing its bulk density and increasing its water holding capacity and porosity (IIT-Kharagpur)
Being alkaline in nature, application of Fly ash/ Pond Ash @ 10 t/ha in combination with organic and inorganic sources increased pH of acid-latertic soil to a considerable extent (IIT-Kharagpur)
In rice based cropping system, repeat application of Fly Ash/ Pond Ash @ 10 t/ha in combination with organic and inorganic sources raised the fertility status of soil, as compared to the treatment of similar combination but without Fly ash/ Pond ash (IIT-Kharagpur)
In general, the available heavy metal status of soil decreased under Fly ash/ Pond Ash based treatments (IIT-Kharagpur)
Application of Fly ash/ Pond Ash increased soil dehydrogease activity, which was more discernible in aerobic condition than flooded/reduced soil condition (IIT-Kharagpur)
RRL, Bhopal (in the project site Dhodhar, Rihand Nagar) found that the nutrient availability was enhanced in soil where 25% coal ash was applied at one time and in those plots wherein addition to the 25% ash was made initially and 5% addition was made every year.
At CAS, Raichur pH & Electrical Conductivity of soil did not differ significantly due to application of different fly ash levels.
CAS, Raichur also found that the combined application of Fly Ash & FYM had a beneficial effect on the fertility status of soil the content of total lead, arsenic and selenium did not change significantly due to application of recommended dose(upto 60 t/ha) of Fly Ash. However, at higher rate of applications the contents of these toxic elements increased marginally.
CAS, Raichur found that the content of toxic elements was lesser in red soils as compared to black soils.
RRL, Bhopal in its trials at Nilgiri, Rihand Nagar (Land- fill site) found that the primary & secondary nutrients were increased in ash filled plots. The heavy metals like Co, Ni, Cr, Pb, Cd where found to be below detectable limits.
CFRI, Dhanbad found that the application of alkaline Fly Ash (pH 8.3) helped in neutralizing the acidic red soil (pH 5.01) making it more productive and suitable for cultivation. It also helped in improving the utilisation efficiency of NPK fertilizer.
Annamalai University found hat application of Lignite Fly Ash in various soil types showed the following types of soil modifications: Neutralising soil pH Increasing EC Increasing available levels of potassium, sulphur and boron.
Effect on quality of yield and uptake of nutrients and toxic elements:
In rice based cropping system, application of Fly Ash/ Pond Ash @ 10 t/ha in combination with organic and inorganic sources increased the concentration of macronutrients (N, P, CA and Mg) in rice grain and edible part of the subsequent crops (groundnut, potato and mustard) as compared to the treatment of similar combination, but without Fly Ash/ Pond Ash (IIT-Kharagpur)
Decrease in heavy metal concentration in grain or edible part of the different crops under Fly Ash/ Pond Ash based treatment is due to dilution effect of these elements through increased grain/edible yield (IIT-Kharagpur)
Radionucleide levels in grain/edible part of rice, groundnut, potato and mustard varied under Fly Ash/ Pond Ash based treatments as compared to the treatments without it and indicated no adverse effect of Fly ash/ Pond Ash (IIT-Kharagpur).
The nutritional value of agricultural produce grown on ash-filled land-fill sites in terms of protein & carbohydrates were found to be comparable with the National Institute of Nutrition-Standards (RRL, Bhopal- trials at Nilgiri, Rihand Nagar)
Effect on ground water:
Application of Fly Ash/ Pond Ash in combination with organic and inorganic sources released lower quantity of Fe and Mn to ground water as compared to the treatment without Fly Ash/ Pond Ash (IIT-Kharagpur).
In ground water samples the level of 286Ra was decreased, 228Ac remained unchanged under Fly Ash/ Pond Ash based treatment as compared to the treatments without it, indicating poor leaching of radionucleide to ground water. Thereby the ground water quality due to application of Fly Ash/ Pond Ash remained unaffected with respect to radionucleide contamination (IIT-Kharagpur).
Other effects:
The crops grown under Fly Ash/ Pond Ash based treatment were observed to be resistant to disease, insect, and pest infestation as compared to the crops grown without Fly Ash/ Pond Ash (IIT-Kharagpur).
At Bakreshwar, in farmers’ field trials the farmers have observed that the crops grown in Fly Ash treated plots were relatively more resistant to pest attack in compared to those in control plots.
Farmers were enthused to take `groundnut’ crop in rabi using Fly Ash as compared to the traditional `boro rice’ crop at Kharagpur for a better `cost-benefit ratio’. Use of Fly Ash as a Mine Soil Amendment The physical effects of fly ash additions on soils were discussed earlier, but relatively high loading rates (> 100 tons per acre) are generally required to significantly influence soil physical properties such as water holding capacity and aggregation. In most instances, fly ash is added to soils primarily to affect chemical properties such as pH and fertility, and loading rates are limited by chemical effects in the treated soils. Plant growth on fly ash-amended soils is most often limited by nutrient deficiencies, excess soluble salts and phytotoxic B levels (Page et al., 1979; Adriano et al., 1980). Fly ash usually contains virtually no N and has little plant-available P. However, newer power plants may be adding ammonia as a flue gas conditioner to limit NOX emissions which may lead to some plant-available N. Application of fly ash to soil may cause P deficiency, even when the ash contains adequate amounts of P, because soil P forms insoluble complexes with the Fe and Al in more acidic ashes (Adriano et al., 1980) and similarly insoluble Ca-P complexes with Class C ashes. Amendment of K-deficient soil with fly ash increases plant K uptake, but the K in fly ash is apparently not as available as fertilizer K, possibly because the Ca and Mg in the fly ash inhibit K absorption by plants (Martens et al., 1970). In some cases, soils have been amended with fly ash in order to correct micronutrient deficiencies. Acidic-to-neutral fly ash has been found to correct soil Zn deficiencies, although alkaline fly ash amendment can induce Zn deficiency because Zn becomes less available with increasing pH (Schnappinger et al., 1975). Fly ash application has also been shown to correct B deficiencies in alfalfa (Plank and Martens, 1974). In some cases, plant yields after fly ash application have been reduced because of B toxicity (Martens et al., 1970; Adriano et al., 1978). Soil amendment with fly ash to alleviate B deficiencies should be carefully monitored in order to avoid B toxicity. Fly ash often contains high concentrations of potentially toxic trace elements. Plants growing on soils amended with fly ash have been shown to be enriched in elements such as As, Ba, B, Mo, Se, Sr, and V (Furr et al., 1977; Adriano et al., 1980). Although trace amounts of some of these elements are required for plant and animal nutrition, higher levels can be toxic. Highly phytotoxic elements often kill plants before the plants are able to accumulate large quantities of the element; which limits their transfer to grazing animals. Elements such as Se and Mo, however, are not particularly toxic to plants and may be concentrated in plant tissue at levels that cause toxicities in grazing animals. Soils amended with high rates of fly ash may accumulate enough Mo to potentially cause molybdenosis in cattle (Doran and Martens, 1972; Elseewi and Page, 1984). Finally, amendment of soil with fresh fly ash may increase soil salinity (reported as soluble salts or electrical conductance-EC) and associated levels of soluble Ca, Mg, Na, and B. Incorporation of 80 T/A unweathered fly ash from a Nevada power plant increased soil salinity 500 to 600% and also caused a significant increase in soluble B, Ca, and Mg (Page et al., 1979). Fly ash that has been allowed to weather and be leached by rainfall for several years generally has much lower soluble salt and soluble B concentrations and is more suitable for use as a soil amendment (Adriano et al., 1982). In general, ashes which have been wet-handled in the plant and stored in ponds will be much lower in soluble salts and B than dry-collected ashes. Use of Fly Ash in Acidic Spoil and Coal Refuse Revegetation Alkaline fly ash can aid in the reclamation of acidic spoils and refuse piles, although one-time ash applications do not appear to be effective in maintaining increased pH if pyrite oxidation is not completely stopped and neutralized. The pH of an extremely acidic surface mine soil and a coal refuse bank in West Virginia was initially raised to near neutral by application of high rates of alkaline (pH 11.9) fly ash. Soil pH dropped 1 to 2 units over the next two growing seasons, however, presumably because of continued pyrite oxidation in the spoils and leaching of Ca and Mg oxides from the fly ash (Adams et al., 1972). Jastrow et al. (1981) used fly ash as an alternative to lime in a greenhouse experiment involving acidic coal refuse. The initial pH of the refuse was 3.5. Amendment with fly ash raised the pH to 4.8, but it dropped to 4.2 by the end of one growing season. In another greenhouse experiment, the application of fly ash to extremely acidic coal refuse resulted in a higher pH and significantly increased barley yields (Taylor and Schumann, 1988). Boron toxicity has been observed in plants grown on fly ash-amended mine spoils, although in some cases toxicity symptoms were apparent but yields were not reduced (Adams et al., 1972; Keefer et al., 1979; Taylor and Schumann, 1988). Jastrow et al. (1981) implicated Mn, Zn, and V toxicity as possible factors in reduction of tall fescue yields on fly ash-amended coal refuse. Coal refuse often contains high levels of trace elements and fly ash application can raise the concentrations of these elements to toxic levels, especially if pH is not controlled. Return to Table of Contents Studies on possible negative effects of Fly Ash application Ground Water
Fly Ashes contain a small amount of trace and heavy metals which may percolate down and pollute ground water. The solubility of these elements is
At Central Fuel Research Institute (CFRI), Dhanbad it was observed that the quality of ground water did not change with the application of flyash and all the parameters including the trace and toxic metal contents were within the permissible limits. Some other research organisations also observed that Fly Ash has no significant polluting effect on ground water.
Uptake of heavy metals and toxic elements by plants
Fly Ash has ppm level concentration of heavy metals, when applied to soil these elements may get absorbed by plants grown on it which may ultimately enter into food chain. However, the absolute quantities of these elements in flyashes are low which may not result into negative effect. The data on trace element uptake and accumulation by plant are limiting. Despite fairly intensive research over the last 25 years, the data on trace element accumulation are rather sketchy and inconsistent. Boron in FLy Ash is readily available to plants and investigators consider B to be limiting factor in unweathered Fly Ash utilisation (Townsend and Gillham (1975); Elseewi et.al. 1978; Ciravolo and Adriano, 1979). RRL, Bhopal conducted a study regarding the uptake of heavy and trace metals by some vegetable crops and it was observed that the uptake is quite low and remains within the normal range.
Central Fuel Research Institute, Dhanbad observed that there is no significant differences in uptake of trace & heavy metal between control and Fly Ash treated plots. Although Fly Ash contain a moderate amount of trace and heavy metals, the uptake and accumulation of these by plants in very negligible.
Radionuclides
There have been several reports in the literature on the presence of radionuclides in Fly Ash but studies on their impact have been few (Coles et.al. 1978; Gowiak and Pacynas, 1980). The radiochemical pollution of Uranium and Thorium series is always present in Fly Ash (Eisenbud and Petrow 1964). The concentration of natural Uranium varies from 14 to 100 ppm although in exceptional cases it may be as high as 1500 ppm whereas that of Thorium is less than 10 ppm. The Fly Ash concentrates besides other gaseous and trace metal oxides, several radioactive contaminants like 222Ru & 220Ru (Sharma et.al. 1989). Bhaba Atomic Research Centre, Bombay is of the opinion that most of the Indian coals has very low levels of radioactivity which is well below the hazardous limit. Hence radioactivity of Fly Ash may not be a limiting factor for its application for agriculture purposes. Central Fuel Research Institute, Dhanbad observed that there is no significant uptake of radioactive elements by plants and also that there was negligible cumulative build up of these contaminants in soil when Fly Ash applied for agriculture purposes.
Conclusions: The potential of fly ash as a resource material in agriculture and related areas is now a well-established fact and more and more researchers and `users’ are getting convinced with its utility potential in this field. The major attribute, which makes Fly ash suitable for agriculture, is its texture and the fact that it contains almost all the essential plant nutrients except organic carbon and nitrogen. Although fly ash cannot substitute the need of chemical fertilizers or organic manure it can be used in combination with these (or in some cases may part substitute their requirement) to the to get additional benefits in terms of improvement in soil physical characteristics, increased yields etc. As in the case with fertilizers and any other agriculture input , the amount and method of fly ash application would vary with the type of soil, the crop to the grown, the prevailing agroclimatic condition and also the type of fly ash available. Although, fly ash has many benefits as an input material for agriculture applications, in view of the fear in the minds of many (regarding the levels of natural radioactivity in Fly Ash and/ the characteristic presence of some amounts of heavy and toxic elements in it) there may be some cautions which have to be taken for the time being while using Fly Ash in agriculture. From the information available till now, there appears to be not much ground for concern on these accounts (heavy metals, radioactivity etc) however further confirmatory studies at the ICAR centers would be helpful in bringing out recommendations in this field. Meanwhile there appears to be sufficient ground now for the cautious and judicious use of this useful material, which is otherwise being wasted/ underutilized. References: Arthur, M.F., Zwick, T.C., Tolle, D.A., and Van Varis, P. (1984) Effects of flyash on microbial Co2 evolution from our agricultural soil. Water Air Soil Pollut., 22, 209. 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