Green Manuring for Soil Health and Sustainable Production of Agronomic Crops
Many countries have got self-sufficiency in food, but continuous cropping and frequent cultivation of soil result in breaking down of crumbs of soil aggregates and destruction of organic matter leading to depletion of soil fertility and productivity. There is substantial decline in use of organic manures including farm yard manure and green manure; therefore, sustainability of soil productivity has become a question. Intensive use of chemical or inorganic fertilizers degrades and emits toxicants that enter the food chain endangering the whole life sustaining system through nitrate poisoning. Applying organic matters either as farmyard manure or as green manure, recycling organic wastes, and enhancing biological nitrogen fixation combined with the use of chemical fertilizers are measures to maintain an adequate level of soil fertility for sustainable crop production. Green manuring is a low cost and effective technology in minimizing cost of inorganic fertilizers and safeguarding soil productivity. Green manuring acts as a restoration factory to maintain the soil fertility for sustainable agriculture. Initial set back may be seen in field crops after the incorporation of organic residues with wide C-N ratio. Green manures can be defined as crops or plants grown and ploughed into the soil to improve soil fertility by the addition of organic matter and nitrogen; or green manures are plants which are grown to improve the structure and nutrient content of the soil; or any crop preferably legume grown and ploughed under to improve the structure and fertility of soil, especially by the addition of organic matter is called green manure.Use of green manure crops in cropping system is called “green manuring” where the crop is grown in situ or brought from outside and incorporated when it is purposely grown; or green manuring is the ploughing under or soil incorporation of any green manure crop, while it is green or soon after it starts flowering. It can also be defined as the practice of growing crop, preferably legume, and ploughing it under at the start of reproductive stage of growth, for improving the structure and fertility of soil; or a practice of adding into the soil undecomposed green plant for improving the physical structure and fertility. A fundamental goal of growing green manure crop is to avoid bare soil between cash crop plantings. This not only protects soil, but also captures sunlight and produces biomass that enhances the soil quality.