Composting of Organic Wastes

Cooperating agency for this topic:
Taichung District Agricultural Improvement Station, Taiwan ROC, 2001-05-01

Compost is an organic fertilizer and soil amendment produced from organic wastes by micro-biological decomposition. Composting is valuable because it changes organic wastes, which would otherwise pollute the earth, into a valuable substance. However, the quality of compost largely depends on how it is prepared. Attention must be paid to the following, in order to get good-quality compost.

Site for Composting

A compost hut or shed is recommended for good-quality compost. This gives some control over the environmental conditions for composting, and prevents the loss of nutrients from leaching in heavy rain. If a compost hut is not available, outdoor sites should be chosen which will offer easy access to a water supply (for wetting the compost), good drainage, and shade (for instance, under a tree).

Materials for Compost

1) Carbonaceous Wastes:

Rice straw, wheat straw, sawdust, sugarcane leaves, peanut stalks, sweetpotato stalks, fallen leaves, chopped cornstalks, corncobs, sorghum stalks, hay, shredded paper etc. (Fig. 1).

2) Nitrogenous Wastes:

Animal manure, oil cake, rice brain, filter cake, green grass clippings, green weeds, vegetable wastes, garbage, digested sewage sludge etc.

Turning the Compost Pile

In general, compost will be ready for use after about 3 months of composting. The degree of biological decomposition varies widely in different parts of the compost pile. It is important to turn and mix the pile every two to three weeks, to get compost of unfirm quality. Mixing should be repeated two or three times during the process of composting. Additional water may be necessary if the materials being composted are too dry.

How to Use the Compost

For annual crops such as wheat, corn, sorghum, sweetpotato, tobacco, vegetables and ornamental flowers, compost should be spread onto the field before tillage.

For perennial crops, such as fruit trees and tea, compost should be spread around the trunk of the tree. Recommended rates of compost application are listed in Table 1.

Caution

• 1) Generally speaking, compost on its own is not enough to meet the entire nutrient demand of crops, especially for nitrogen. Chemical fertilizers, therefore, should also be applied in addition to compost. The rate at which each nutrient element should be supplemented depends on the quality of the raw materials used in the compost. It is recommended that extension staff should be asked about which kind of chemical fertilizer, and how much, should be supplied in addition to the compost.
• 2) Some kinds of organic waste, especially food processing wastes and sewage sludge, may not be suitable as raw materials for compost because of their high content of heavy metals or their acidity. Care must be taken with new kinds of organic materials which are being composted for the first time.

Index of Images

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  Figure 1 Some Ingredients of Compost

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  Table 1 Recommended Application Rate of Compost for Various Crops in Taiwan <BR>

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