What is Green Manure?
The practice of ploughing or turning into soil under-composed green plant tissue for the purpose of improving physical condition as well as fertility of the soil is referred to as green manuring and the manure obtained by this method is known as green manure.
The green manure crop should possess the following desirable characteristics:
The green manure crops should
- have profuse leaves and rapid growth early in its life cycle.
- have abundance and succulent tops
- be capable of making a good stand on poor and exhausted soils.
- have a deep root system.
- be legume with good nodular growth habit.
Use of leguminous green manure crop is more useful in comparison to non-legumes, as more nitrogen is added by legumes. This will be advantageous for the soils and crops grown after green manuring.
Crops Suitable for Green Manuring
Crops suitable for green manuring are divided into two groups:
Non-legumes or Non-leguminous crops: The non-legumes used as green manuring crops provide only organic matter to the soil. The non-legumes are used for green manuring to a limited extent. Examples:Mustard (Brassica Sp), Wheat (Triticum Sp), Radish (Raphanus sativas), Carrot (Dancus carota), Jowar (Sorghum Vulgare) Maize (Zea mays), Sunflower (Hellanthus annus), etc.
Legumes or Leguminous Crops: The legumes used as green manuring crops provide nitrogen as well as organic matter to the soils. Legumes have the ability of acquiring nitrogen from the air with the help of its nodule bacteria. The legumes are most commonly used as green manuring crops. Examples:Sannhemp (Crotalaira juncea), Djainach (Seshania aculata) Mung (Phaseolus aureus), Cowpea (Vigna catjung), Lentil (Lens esculenta), Senji (Melilotus alba), Berseem (Phaseolus aureus) Guar (Cyamposis tetragonolaba)
Benefits of Green Manuring:
There are numerous advantages of green manuring:
Supply of Organic Matter: Green manure supplies organic matter to the soil. The organic residues from green manure also help to provide the stability of soil structure needed for optimum plant growth. Humus formed from green manure increases the absorptive capacity of soil, promotes aeration, drainage and granulation, which help the plant growth. Green manuring improves the structure of the soil. Organic matter stimulates the activity of soil micro-organisms.
Addition of Nitrogen: The green manuring crop supplies additional nitrogen to organic matter, if it is a legume crop, which has the ability to fix nitrogen from the air with the help of its root nodule bacteria (e.g. Rhizobium). The legume crop adds nitrogen for the succeeding crop. So all the legumes crop leave the soil in better physical condition and richer in nitrogen content. They return the plant nutrients of deeper layers to the upper top soil.
Nutrient and Soil Conservation: Green manuring crops act as cover crop. They protect the soil from erosion and nutrient loss by taking up soluble nutrients which might otherwise have been lost in drainage water or due to erosion. Green manuring crops make available phosphorous and other nutrients for the succeeding crops. Green manure has a marked residual effect also.
Increases the biochemical activity: The organic matter added to soil by way of green manure acts as food for micro-organisms. The organic matter stimulates the activity of micro-organisms and they stimulate the biochemical changes accordingly.
Green manuring increases crop yield: Green manure increases the organic matter and nitrogen content (in case of leguminous green manuring crop) of the soil. It is proved that if green manuring is done properly, it always results in increased yields of the succeeding crops.