Soil fertility Management in Organic Farming

The followings are practised to improve soil fertility
* Organic fertilizers
* Green Manures
* Crop rotation
* Land fallowing
* Mulching

Organic fertilizers improve soil structure, increase the level of organic matters and add nutrients to the soil. Examples are farm yard manure, animal dungs, poultry wastes, kitchen wastes and compost.

Compost
Different organic materials are mixed together to achieve a balanced nutrient composition and structure that provides good aeration.

Compost making materials:
* Plant materials - combination of Nitrogen rich and Carbon rich materials
* Animal dungs - Cow and pig dungs are rich in potassium and phosphorus, poultry dropping is rich phosphorus.
* Wood ash - contains K, Na, Mg, Ca and other macro and micro nutrients
* Rock phosphate - binds to the organic materials
* Add small quantity of soil, esp soil rich in clay to improve the quality of the compost.

Green Manure - The practice of incorporating green plants into the soil through ploughing and ridging. The green plants, usually leguminous cover crops are incorporated to the soil to improve soil structure and increase soil fertility. Cowpea (Vigna unguiculata) is commonly used. Nitrogen fixing bacteria in the root nodules of leguminous plants tap and transform atmospheric nitrogen to plant nutrients. The leaves and twigs of nitrogen fixing plants are rich in nitrogen and other plant nutrients, thus they are a good source of fertilizer.

Old and coarse plant materials may not suitable for management of soil fertility because they don't break down readily, and the nitrogen may be immobilized (not available for plant).

Crop Rotation
Different crops are planted on the same piece of land in sequential seasons. This practice  improves nutrient status of the soil and breaks the cycle of pests and diseases when leguminous spp and resistant spp are planted in sequence with other crops.
* Crop of similar feeding pattern and physiological characteristics should not follow each other.
* Maize, sorghum, rice and cassava should be rotated with soybean, ground nut or melon.

Mulching is the process of covering top soil with plant materials such as leaves, twigs, straw, crop residues and wastes of agro processing to improve soil structure and reduce runoff; increase aeration, organic matter, fertility of the soil and suppress weeds. The mulching materials used for these purposes are biodegradable organic materials.

Selection and use of mulching materials should be done with care to prevent buildup and spread of pests and diseases. Some plant residues harbour destructive organisms. For example, stem borers may survive in the stalks of corns, sugar cane and cotton. Mulching materials may also cause termite infestation.

Land fallowing is when a piece of land is left to rest and restore soil fertility for a period of 3 - 5 years.