In recent years the use of chemical fertilizer has been discouraged due to environmental pollution, rising costs and toxic effects. Therefore ,the fertilizer of biologiIn recent years the use of chemical fertilizer has been discouraged due to environmental pollution, rising costs and toxic effects. Therefore ,the fertilizer of biological origin are use to avoid such hazards as they are environment friendly, non toxic and cost effective.
The living organisms which are used as fertilizer to improve the fertility of the soil are called fertilizer of biological origin. They are grouped into two main categories :-
a. Green manures b. Bio fertilizers
a. GREEN MANURES : Green manuring is the practice of cultivating quick growing crops and ploughing them back under the soil to improve soil fertility and productivity. It is cheap and the best method to increase soil fertility. Green manures add nitrogen and easily decompose let organic matter to the soil . They supply practically all nutrients required by the crops . They improve the physical and biological status of the soil by improving aeration , drainage and water holding capacity. Being able to bind the soil ,they also check soil erosion and leaching
The green manuring increases the crop yield by 30% - 50% .Usually , leguminous crops are used for green manuring. Some plants used for green manuring are listed here :-
- Crotalaria juncea
- Sesbania aculenta
- Lens esculenta
- Cyamopsis tetragonobola
- Vigna sinensis
- Trifolium alexandrium
- Lathyrus sativus
- Macrotyloma uniflorum
b. BIOFERTILIZER : The green manures are not sufficient to meet the existing needs of agriculture and therefore, they are supplemented by the use of bio fertilizer. The living organisms which are commonly used to maintain and improve soil fertility are called bio fertilizer. The main source of bio fertilizer are bacteria,Cyanobacteria and fungi. These organisms add nutrients to the soil due to their biological activity and improve fertility of soil.