Green manuring

Green manure

The crops raised and left-over after uprooting or ploughed in the field to improve the soil health are called as 'green manure'. These crops are fast-growing and their biomass enrich the soil nutrients, particularly, organic carbon and nitrogen. Such crops are grown as 'Jayad' crop between the ‘Rabi’ and ‘Kharif’ crops in annual cropping system and during spring season between the fall the summer crop.

Green manuring

Green manuring is the practice of growing green manure crops to enhance the soil fertility and soil health. This is a rather old practice being done since the ancient period. However, since the intensive use of chemical fertilizers after the green revolution, green manuring practice has been ignored and farmers paid for such practice in the form of decreased soil fertility.

Advantages

• Green manuring enrich the soil nutrients particularly, organic carbon and nitrogen.
• This practice protect the soil from erosion during the erosion-prone season of the year.
• It occupy the soil surface and thus, control the weeds.
• Green manure efficiently utilizes the nutrients remains from the preceding crops and prevent leaching of soluble nutrients.
• Cover crop raised as green manure work as live much, while, the remains left from decomposition of green manure crops work as mulches.

Types of green manure crops

Leguminous crops

These crops belong to clover family (Fabaceae). Roots of these plants are associated with nitrogen-fixing bacteria, which fix atmospheric nitrogen into the plant-available form. These bacteria include Rhizobium and Sinorhizobium, which are symbiotically associated in the root-nodules.
Leguminous crops are ploughed and mixed in the soil to release fixed nitrogen. Clover, beans, peas, vetch, etc., are common leguminous crops raised as green manure. Some of these crops are mentioned here in details.

Dhaincha

Dhaincha (Sesbania) grown as green manure

Dhaincha (Sesbania aculeata syn = Sesbania bispinosa and S. rostrata), is a fast growing small (reaches up to 7 meters) annual shrub native to South Africa and Asia. This crop is well-adapted to various edapho-climatic conditions. The crop can be easily grown under wet, heavy, sandy, saline soils.
About 20 kg seed of dhaincha is recommended for sowing in 1 hectare of land. Dhaincha grows very luxuriantly and 8 to 10 weeks after sowing, the crop can be incorporated into the soil. It gives best result, if grown before 55 to 60 days of rice farming. 1 meter tall dhaincha crop roughly yield 25 tons of fresh biomass per hectare producing about 125 kg of fixed nitrogen to the soil. This significantly reduces the dependency on nitrogenous fertilizer.

Non-leguminous crops

These crops do not provide fixed nitrogen to the soil, but their biomass enhance the organic carbon in the soil. Buckwheat, oat, rapeseed, annual rye grass, winter wheat, etc., are common crops raised as green manure.

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Content first created on 10-06-2020
last updated on 07-05-2021