Fertilizers of biological origin

Soil contains various nutrients that are essential for growth and development of plants. Constant use of leads to the loss of its important nutrient and ultimately its fertility. Deficiency of any one or more nutrients ultimately affects the yield of crop plants.

There are the several method to increase the soil fertility. Farmers usually apply chemical fertilizers to enhance soil fertility. However, frequent application of chemical fertilizer is equally harmful to the soil as they affect the soil composition and nutrients. Therefore, in order to reduce the hazards caused by chemical fertilizers, the recent trend to make use of the fertilizers which are environment friendly and are of biological origin. Materials of biological origin which are commonly used to maintain and improve soil fertility are called biofertilizers. There have been grouped into two main categories-
1. Manures
2. Biofertilisers

Both when added to soil increase in nutrient value especially the nitrogen content and thus enhance the crop productivity.

Manures
Manures are the organic materials when added to soil increases its nutrients value especially the nitrogen content and thus enhance the crop productivity. The manures are of three types:
• Farmyard manure – It is the most valuable organic matter commonly applied to the soil. It consists of mixture of cattle dung and crop residues like remnants of the straw and plant stalks fed to cattle. The cattle dung is to properly stored in a pit. The pit of one meter depth is to be dug under the shade and the dung is kept moist. The surface is plastered with mud. The manure becomes ready for use after 2-3 months.
• Composite manure – It consist of rottened vegetables and animal-shed wastes, refuse, farm weeds and other substances. These are properly mixed and used after rottening or decomposition.
• Green manures – Green manures are the green crops which are the back under the soil. Thus, green manuring can be defined as the practices of growing, plugging under and mixing of green crops with soil to Improve soil fertility and ultimately crop productivity. It also provides a protection action against soil erosion and leaching. There is 30-50% increase in the crops yield by using green manure. Some of the commonly used green manures are mainly leguminous and non-leguminous.
Cowpea, sun hemp, dhaincha, berseen, lentil (Mansur)

Important of green manure in agriculture
1. Green manures are the cheapest and easily available source or fertilizers.
2. They provide the additional nitrogen as well as other organic matters to soil.
3. They supply practically all the nutrient required by the crops.
4. They check soil erosion, leaching and percolation.
5. They increase the crop yield from 30% to 50%.
6. They improve soil aeration and drainage condition.


Prospectus of green manure in Nepal
Since there is no fertilizer factory in Nepal, the use of green manures can be the only supplemental source of fertilizer especially for nitrogen fertilizers. Dr. Bhola Man Singh Basnet of Nepal Agriculture Research Council (NARC) khumaltar has extensively carried out his research on green manure using Sesbania which is called locally as Dhanicha.

Sesbania can be successfully grown and incorporated in the soil. It has been estimated that by the use of sesbania, the yield of paddy has increased from 21 to25%. Therefore, green manure can very good source of fertilizer in Nepal.