कृषि स्रोतों से उत्सर्जि‍त ग्रीनहाउस गैसों का शमन 

Word agriculture contributes about 4% to total carbon dioxide emission, the most important green house gas. Factor such as soil texture, temperature, moisture, PH, available C and N influence Co₂ emission from soil. The rate of Co evaluation is greater from clay-loam soil, which has highest organic C content than sandy soil, more Co₂ emission occurs from a tilled than from an undisturbed soil (no till) .

Temperature has a marked effect on Co₂ evolution from soil by influencing root  and soil respiration and on CH₄ by affecting anaerobic carbon mineralization and methanogenic activity. 

Methane is about 20 times more effective than co2 as a heat trapping gas. Primary sources of methane from agriculture include animal digestion processes, wetland, paddy cultivation as well as manures storage and handling.

In ruminant animals methane is produce as a by- product of the digestion of feed in the rumen of cattle under anaerobic conditions. Methane is also produced during manure management when animal waste is shared in anaerobic conditions and left to decompose in the field. Anaerobic conditions develop in wetland rice fields, which limit the transport of oxygen into the soil, and the microbial activities render the water- saturated soil practically devoid of oxygen.

The biogenic methane results from the metabolic activities of a small but highly specific bacterial group called methanogens. Their activity is increased in submerged conditions, water management play a major role in methane emissions intermittent irrigation reduces the methane emission on by one- tenth as compared to continuously submerged conditions.

Soil as considered to be contributing 65% of the total nitrous oxide emission The major sources are soli cultivation, fertilizers and manures application, and burning organic  material and fossil fuels from agricultural perspective , nitrous oxide emission from soli represents a loss of soli nitrogen , reducing the nitrogen (N)  use efficiency.

Global warming potential of green house gasses from Indian agriculture

The effectiveness of each green house gas to trap heat in the atmosphere varies. Global Warming Potential (GWP) is an index defined as the cumulative radioactive forcing between the present and the some chosen later time ‘horizon’ caused by a unit mass of gas emitted now . The GWP of different GHGs is measured relative to co2 that is 21 for CH₄ (based on a 100 year time horizon )  and 310 for N₂O.

India Agriculture as whole as contributed only 3.2% of the world total methane emission of which 25% is from agricultural soil. The nitrous oxide emission is miniscule in the contribution of Indian agriculture, our estimates using indigenous emission coefficient have shown that the Indian agriculture soils are contributing only 0.88% of world nitrous oxide emission. Methane and nitrous oxide from Indian agricultural soli are responsible for only about 0.23% and 0.1% respectively, of the global warming caused by worlds methane and nitrous oxide emission .Thus, overall green house gas emission from Indian agricultural soils is very small fraction of the total world green house gas emissions.

Mitigating greenhouse gas emission from agricultural source

Mitigating methane and nitrous oxide.

Enteric fermentation from ruminant livestock : Methane emission are related to the proportion of diet that is grass, legume, grain and concentrates and the characteristics of different feeds (e.g. soluble residue, hemicelluloses and cellulose content) mitigation of methane emitted from livestock is most effectively approached by strategies that reduced feed input per unit of product output. Nutritional, genetic and management strategies that improve feed efficiency increase the rate of product (milk, meat) output per animals. Because most CH₄ is produced in the rumen by fermentation, practices that speed the passage of feed from the rumen can also reduce methane formation.

Rice cultivation: Altering water management practices particularly mid- season aerobic by short term drainage can greatly reduced methane emission in rice cultivation. Improving organic matter management by promoting aerobic degradation through composting or incorporating into soli during off season drain period is another promising technique.

Agricultural soil : Appropriate crop management practices which leads to increase N- use efficiency and yield hold the key to reduced nitrous oxide emission ,site specific nutrient management ,fertilizers placement timing, proper type of fertilizers are some of the practices that supply nutriments in a better accordance with plant demand. plant uptake of N can be improved and total N losses can be reduced by deep fertilizers placement and by banding fertilizers within the crop rows.

Manure management: Using covered legumes suitable of large scale, intensive farming operation can reduce emission from livestock waste. Solid rather than liquid manure handling may reduce methane but promote nitrous oxide formation. Appling manure to land as soon as possible reduced the emission aerating manure during composition may reduce methane but increase N₂O formation.

2. Mitigating carbon dioxide:

Carbon can be sequestered in soils by increasing C inputs and or decreasing their decomposition. Carbon sequestration in soil can also be increased through manipulation of soil p^H, soil water content, and temperature setting aside, surplus agricultural land, and restoration of soil carbon on degraded lands. This can also be enhanced by reduced tillage, and greater allocation of land to agro-forestry and bio-fuel crops.   

Authors:

Prof.  Sevak A. Dhenge¹ and Prof.  Kedar V. Swami²

Late R.G.Deshmukh College of Agriculture, Tiwsa,

Dist- Amravati – 444903 MAHARASHTRA

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