Manures contain large quantities of organic matter and supplies small quantities of nutrients to the soil. It is prepared naturally by the decomposition of animal waste, excreta and plant waste.

• It helps in the soil enrichment with nutrients.
• It helps in improving the soil structure.
• It helps in increasing the water holding capacity in sandy soils.
• In clayey soils it helps in the water drainage and prevent water logging.

Manure is classified based on the kind of biological material used to make it as :

(i) Compost

(ii) Vermi-compost

(iii) Green manure

(i) Compost: The farm waste and livestock excreta, along with vegetable waste, sewage waste, weeds, straws etc. are allowed to decompose in a pit is called compost. The compost is rich in nutrients.

(ii) Vermi-compost: When the above given matter is allowed to decompose in the pit along with some earthworms, the decomposition speeds up and is called vermi-composting.

(iii) Green manure: Some plants like sun-hemp or guar are grown and then mulched by ploughing them into the soil. This is done before the sowing of crop seeds into the field.

These green plants present in the soil acts as green manure which enriches the soil in nitrogen and phosphorus.