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Bulletin of the National Institute of Ecology 23: 0-00, 2012

ISSN: 0379-7937 (Print); (Online)

National Institute of Ecology, Jaipur and New Delhi

Use of Fly Ash in Agriculture

R. B. Singh

President, National Academy of Agricultural Sciences, New Delhi

Email:

Fly ash, the residue of combustion of coal, originally a mixture of vegetation, clay androcks, comprise of a wide range of inorganic matters. Collection of this material is

accomplished mainly using electrostatic precipitators. Non-captured fine particulates are

either collected by additional scrubbing devices or emitted to the atmosphere and fall out

in the environ surrounding power generating plants.

Approximately 260 million tons of coal was consumed per annum by 82 utility

thermal power plants in India (2003-04). It constituted nearly 70% of the total power

generation, which in turn produced 108 million tons of fly ash per annum. The annual

generation of fly ash is projected to exceed 175 million tons per annum by 2012

(considering the plants to double the power generation over next 5-7 years). As per the

estimates of Ministry of Power as well as Planning Commission, up to the year 2031-32

the coal requirement and generation of fly ash would be around 1800 million tons and 600

million tons respectively.

The large volume of fly ash occupies large area of land and possesses threat to the

environment. As such there is an urgent need to develop technologies for its gainful

utilization and safe management on a sustainable basis. Agriculture and wasteland

management have emerged as prime bulk utilization areas for the fly ash in the country.

Physically, fly ash occurs as very fine spherical particles, having diameter in the

range from few to 100, low to medium bulk density, high surface area and sandy silt to

silty loam texture. Chemically, fly ash is amorphous ferro-alumino silicate mineral with

major matrix elements like, Si, Al, Fe together with significant amount of Ca, Mg, K, P, S.

The concentration of total and available trace/ heavy metals and radionuclides in fly ashsamples is in traces and their availability / leachability is negligible. The texture and

physico-chemical properties including trace/heavy metals and radioactivity closely

resemble with mot of the field soils. The pH of fly ash has been reported from 4.5 to 12.0.

FLY ASH AND CROP YIELD

The key to management of waste products, regardless of their sources, is to find means by

which they can be recycled and used beneficially. Fly ash addition generally decreases

bulk density of soil which in turn improves soil porosity and enhances water retention

Special Issue: Fly Ash in Agiculture(Eds: P.S. Pathak & V.K. Misra)

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capacity. The strong correlation between pH correction and nutrient availability in soil

suggests that in fly ash, most elements are associated with the mineral phase. It is therefore

expected that interaction between the predominantly inorganic fly ash and organic matter

may further enhance its beneficial effect on plant growth in problem soils. Addition of

organic matter has an additive effect as it reduces the concentration of toxic metals

through sorption, lowers C:N ratio and provides rganic compounds which promote

microbial proliferation and diversity.

Large-scale field demonstration / application of use of fly ash in agriculture on

cultivation of different cereal crops, pulses, oil producing crops, sugarcane, cotton,

vegetables, etc. under different soil-crop combinations and agro-climatic conditions have

been taken in the country along with different R&D institutes/universities and farmers

across the country. Various crops grown, locations and yield increased due to fly ash

application over control (without fly ash) are given below in Table-1.

Table 1. Impact of Fly Ash on Crop Yield: Field Results*

Crops (No. of Sites) Location Yield increase

(percentage)

Arhar-Wheat (1) Bhatinda 30-50

Cotton, Shorgum, Soyabean, Groundnut, Wheat Vidarbha (Maharashtra) 10-46

Cotton-Rice (1) Vellampudugai 20-30

Groundnut Neyveli 20-30

Maize-Onion, Rice-Sunflower (1) Angul 18-30

Mustard, jute (1) Farakka 20-40

Mustard, Potato, Lentil (1) Bakreshwar 20-30Mustard-Rice (1) Kharagpur 10-25

Pearl, Millet, Wheat Hissar (Haryana) 20-32

Rice (2) Mustard, Groundnut, Potato (1) Balarampur, Gholghoria,

Burari

8-12

Rice, Groundnut-Mustard (1) Kharagpur 18-25

Rice, wheat (2) Farakka 15-30

Rice, wheat (4) Bakreshwar 15-25

Rice-Green Gram (1) Sathamangalam 15-25

Rice-Groundnut (3) Kharagpur 15-25

Rice-Wheat (1), Cotton-Wheat (1), Sunflower-Maize

(1) Wheat-Rice (1)

Ropar, Bhatinda 15.25

Sugarcane Childambaram 18-25Sugarcane Neyveli 20-25

Sunflower (1), tomato (1), Potato (1), Wheat (1),

Berseem (1), Red Gram (1), Maize (1), Rice (1)

Nilgiri, Rihand Nagar 15-35

Sunflower-Groundnut (2) Raichur 20-40

Sunflower-Maize (2) Raichur 15-25

Tomato (1), Cabbage (1), Potato (1), wheat (2), Pea

(1)-Maize (6), Wheat Maize (2)

Dhodhar, Nilgiri, Rihand

Nagar

20-40

Wheat Ropar (Astalpur) 15-20

Wheat, Mustard, Rice, Maize Dadri (UP) 6-18

Wheat-Maize, Soyabean-Maize, Lemon Grass (1) Sarni 15-25

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Thus, it is apparent that application of fly ash increased production of cereals, oil

seeds, pulses, cotton and sugarcane, etc. by 10-15%, vegetable by about 20-25% and root

vegetables by about 30-40%.

FLY ASH ON DEGRADED LAND

Soil degradation in India is a serious problem. Large area of land is affected by soil and

wind erosion and by desertification. Fly ash works as an excellent soil conditioner/

modifier and helps to a great extent for restoration of degraded land into agriculture land

wherein different types of crops/forestry species/horticulture species could be grown on

sustainable basis.

The possible way of using the fly ash is as a sodic soil amendment by increasing

the soluble Ca+ commutation in soil. Use of fly ash, for reclamation of saline-alkali (usar)

soils of Phulpur, IFFCO (up to 75% par-substitute of gypsum), and its use along with

mycorrhiza for reclamation of eroded impervious alkaline-saline soils/ threatened land inarid zone (Jaipur) has been successfully demonstrated. Fly ash also enhances growth of

commercial as well as conventional forestry species. It is reported that fly ash is a feasible

alternate to gypsum for amelioration of sodic soil. However, because of the variability in

fly ash characteristics specific site condition need to be considered for determining fly ash

application rate for treatment of sodic soil.

OTHER IMPACTS OF FLY ASH

In addition to increase in the yield of produce, significant increase in biomass yield hasalso been found. Farmers have also reported that the size of grains and their luster get

improved with application of fly ash, resulting in better quality marketing assessment

interalia better realization. The significant improvement has been reported by farmers

regarding pest control especially in case of rice & sugarcane, due to fly ash application. A

number of farmers reported that there was no soil born pest attack due to fly ash

application. The presence of calcium, magnesium, sulphur, iron and other nutrients in most

of the fly ash samples was found to improve the quality of crop produce in respect of

protein and oil content.

ASSESSMENT OF IMPACT OF HEAVY METALS

Samples of hopper ash as well as pond ash were analyzed from a large number of thermal

power stations for total and available heavy metals content and their leachability /

availability. The detailed analyses and evaluation reveal that the concentration of metals

present in fly ashes and their leachability/ availability is too small to make any significant

impact on soil-cropping system.

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TOXICOLOGICAL STUDIES

The detailed laboratory and clinical studies have been taken up at National Institute of

Nutrition (NIN), Hyderabad, under Indian Council of Medical Research (ICMR), Ministry

of Health, GOI, to evaluate the produce grown on fly ash treated plots for the toxicological

impact. The laboratory analyses reaffirm the earlier findings of insignificant impact of fly

ash in respect of heavy metal contents in agricultural produce. Clinical evaluation has also

been done through haematological and histopathological studies. Two groups each of 12

rats (weanling WNIN) & 12 mice were taken for the study, as per WHO protocol. The test

groups were fed with produce grown on fly ash treated soil and the control group of

animals were fed with same composition of food from control plot. The physiological data

regarding weight, growth, etc were recorded at regular intervals. Blood and tissue samples

were tested as per the protocol. Animals were scarified and various organs tested. The tests

& evaluation revealed that there is no toxicological impact to any of the organs of both rats

and mice fed on crop produce grown with fly ash.

NUTRITIONAL EVALUATION

Evaluation of nutritional value of agricultural produce grown on fly ash treated soils and in

the control plots was also taken up at NIN, Hyderabad. The results revealed that there is no

adverse effect of addition of fly ash, on the contrary there is an advantage; the protein, iron

and calcium contents are higher in the produce of fly ash treated plots and trace/heavy

metal concentrations in the produce is not at all affected by fly ash addition. This is

desirable as it is good for human being.

EVALUCTION OF RADIOACTIVITY

Samples of fly ash, soil, grain and biomass from fly ash treated plots as well as the control

plots under the projects undertaken/ supported by FAM/FAUP have been evaluated for

their radionuclide contents at Institute of Physics (IOP), Bhubaneshwar, Deptt. of Atomic

Energy, Government of India. The results revealed that the application of fly ash has no

significant impact on field soil, and agricultural produce and biomass.

POTENTIAL OF VERMICOMPOSTED FLY ASH IN AGRICULTURE

Vermicomposted fly ash developed at Soil Testing Laboratory, Institute of Agriculture,

Visva Bharti University, (W.B.) is an improvised produced fly ash and humified organic

wastes, facilitated with the help of the intestinal microflora of epigeic earthworms. This

material exhibits considerably higher availability of different plant nutrients which leads to

production of good crop and reduced use of mineral fertilizers. A good share of this

increased availability of different nutrients in vermicomposted fly ash comes from fly ash

alone thus improving upon its original quality with regard to supply of plant nutrients.

Application of this vermicomposted fly ash in agricultural fields has shown considerable

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potential in reducing the quantum of application of mineral fertilizers. Since

vermicomposted fly ash is a good source of phosphorus and potassium, which comes from

fertilizers, largely imported from abroad, large scale adoption of this practice is likely to

have a positive effect on the economy of the country also.

ISSUES

Long term research on saline sodic soils to understand the spatio-temporal dimensionsof the fly ash dose and frequency for different edaphic conditions in different climatic

conditions.

Large scale operational research in partnership mode involving researcher farmer development departments and NTPC to demonstrate the value of fly ash for improving

land productivity and address the socio-economic issues including the policy.

Policy on support for the transport of fly ash from the thermal power stations to distantsites since it involves large quantity application.

Fly ash as career of biofertilizers and nutrients through vermicomposting technologydevelopment for sustainable organic farming and cleaner environment.

Fly ash use and blending with insecticides for plant protection to minimize thechemical load in agriculture.

Environmental issues related to fly ash production, collection, transport andapplication need detailed lifecycle analysis to manage the system and its health.

Fly ash use based ecotechnology development for improved crop production and soilhealth.