The plant residues that remain in the field after harvest often still contain pests or diseases. They form consequently a source of infection for the next crop. For this reason the destruction of crop residues after the harvest is often recommended.
Example (insects):
Stalk borers are insects that pass the dry season as caterpillars or pupae in stubbles or old stalks. Inside the stalks they are well protected against the sun and against their natural enemies. At the beginning of the next growing season they become active and the emerging adult moths can infest the new crop. To reduce or avoid this infestation, the farmer can take measures to reduce the number of insects that survive the dry season within the stalks.
Destroying the crop residues is very effective, because along with them also the insects and diseases that are present are destroyed. There are several possibilities:
- Burn the stalks and crop stubbles
- Burry (deeply) the stalks and crop stubbles
- Use the crop residues to make compost
- Feed the stalks and stubbles to animals
There are situations where the farmer does not want to destroy the old stalks, for example in cases where they are used as building material or to make fences. It is then recommended to dry the stalks by placing them flat on the ground in a thin layer. By exposing them in this way for a prolonged period to the sun, a substantial number of insects will not survive.
Using the crop residues to make compost is especially interesting in the cultivation of vegetable crops. The compost can be used to improve the structure and fertility of the soil.
In cases where there is no urgent need to destroy the crop residues, it is usually better to keep them in the field and mix them with the soil in order to improve soil quality and organic content of the soil. For example in rice fields it is probably better to plough the crop stubbles into the soil instead of burning them.