Using organic materials and manures
What are organic materials and manures
Organic materials and manures come from plant or animal wastes or by-products such as cattle or poultry manure, composted rice straw or other crop residues, sewage sludge, oil cakes, green manures, and legume clippings.
How to use organic materials and manure
Organic materials or manures are normally applied uniformly across the field, two or more weeks before being incorporated into the soil during land preparation. Sometimes rice straw is directly composted in the field.
Why use organic materials and manures
Manures and other organic sources are used to improve soil fertility and soil organic matter content and to provide micronutrients and other growth factors not normally supplied by inorganic fertilizers. Application of these materials may also enhance microbial growth and nutrient turnover in soil.
How much do I apply?
Applications of organic material can be difficult as it:
- can be bulky, with high handling and transport costs.
- may have high costs per unit of nutrient.
- is not always available.
- has to be applied at the beginning of the crop (thus early applications may not meet later crop demand for nutrients).
- can have an unpleasant odor, making it undesirable for farmers and others.
Combining organic manure and fertilizer
It is advisable to combine the use organic manures with the application of inorganic nutrient sources as needed. This allows farmers to use organic materials or manure available on-farm at low cost to supply a portion of the crop’s demand for nutrients and improve soil fertility where required. The use of organic manures available on-farm can return high yields and profit when combined with inorganic fertilizer, particularly on upland or poor lowland soils. However, it is often not profitable to buy organic fertilizers even if they are sold as fortified organic fertilizers, which is a ready mix of organic and inorganic fertilizers.