Manure and other organic fertilizers are recommended to improve the fertility of the soil and to improve soil structure. Generally, the use of manure will favor the development of the plant, which helps it to resist attacks of pests. A well-developed plant can better support these attacks without suffering much damage, while a poorly developed plant is much more vulnerable to attacks of insects and diseases. The use of manure will thus help the crop to better resist the attacks of pests.
While synthetic fertilizers could also provide nutrients for the crop, organic manure has the added advantage of keeping the soil healthy. It will favor the development of antagonistic fungi that help to reduce diseases and even nematodes.