Submitted by kiran yadav
Building of organic matter and improved soil structure:
A major benefit obtained from green manuring is the addition of organic matter to the soil. Reported increases of soil organic matter (SOM) following GM use often range between 0 and 1% of total soil mass.
Nitrogen fixation from legumes is the key benefit of growing leguminous green manure crops. The portion of green manure nitrogen available to a succeeding crop is usually about 40% to 60% of the total amount contained in the legumes.
Enhanced soil microbial activity:
A rapid increase in soil micro organisms occurs after a young, relatively lush green manure crop is incorporated in to the soil. The soil microbs multiply to attack the freshly incorporated plant material.
Enhanced availability of native soil nutrients:
Besides addition of nitrogen, legumes help in recycling of other nutrient on the farm. Nutrients are accumulated by green manure crops during a growing season. When the green manure is incorporated , or laid down as no-till mulch, these nutrients become slowly available during decomposition. Green manures scavenge nutrients from the subsoil and translocate them upwards to the surface rooting zone, where they become available to the succeeding crop.
Improvement in soil physical properties:
Green manuring has favourable effects on soil physical properties. The soil physical properties that are affected by incorporation of the green manure include the structure, moisture retention capacity, consistency and density.
Benefits of rooting action:
The extensive root system of some green manure crops is highly effective in loosening and aerating the soil. When GM crops are planted after a sub-soiling treatment, they help extend the soil-loosening effects of the sub soiling treatment.
Green manure crops occupy the vacant space and light and there by shade the soil and reduce the opportunity for weeds to establish themselves.
Soil and water conservation:
The soil conservation benefits provided by green manure crops extend beyond protection of bare soil during non-crop periods. The mulch that results from a chemically or mechanically incorporated GM crop increases water infiltration and reduces water evaporation from the soil surface.
Enhanced crop yields:
A large number of field experiments have been conducted to study the effect of green manuring on the growth and yield of various succeeding crops. The results obtained for some crops have indicated an increase of 20-50% in grain yields. The beneficial effects of green manuring on yield though vary from crop to crop. Rice is benefitted most; wheat is next, while increase in cotton and sugarcane yield is relatively smaller.
Reference: Kumar. Dinesh and Shivay, Y.S (2007). "Green Manuring: Benefits, Management and Constrants". Kurukshetra, vol.55, No. 4.