Effect of intercropping on disease severity in organic farming

Summary

In order to improve plant quality in organic farming, DARCOF launched studies on crop management, and among them, research on intercropping, defined as the growing of two or more species simultaneously in the same field during a growing season.
The aim of this study was to evaluate the effect of intercropping on disease severity. The fist part of this report presents the context of this study and the research center where this work took place. Then, the literature review approaches the different systems on which intercropping is based. This is followed by methods used and the results. To finish, a discussion points out the conclusions of this work and its limitations.
In this study, the levels of all diseases were very low. Intercropping had a significant effect on one disease: Chocolate spot on faba bean. This was the only disease where levels above 10% were recorded. Thus an important result of this study is that the effect of intercropping on disease severity is directly linked to the level of disease in the field. If the percentage of leaf area affected is lower than 10% the effect of intercropping can’t be observed.
However, many other factors influence the response of intercropping to disease severity:
- the component crops chosen: some crops appear to compliment one another better with respect to disease than other one ,
- the density of the component crops,
- the cultivars of both the host plant and the companion crop,
- the resistance induced by the companion crop,
- the microclimate providing more or less favorable conditions to disease development, or
- other factors particular to each cropping system.
All these factors and mechanisms induced by this system should be studied in order to improve crop quality in organic farming by intercropping, and thus make it adopted by farmers. This knowledge is a tool which will help farmers to choose cropping systems adapted to specific farm systems (pedo-climatic conditions, animal feed, equipment available, etc).
Moreover, intercropping, with its different benefits based on ecological principles, is a sustainable way to improve the general farming system in Europe. Intercropping constitutes a concrete means to increase the diversification of agricultural ecosystems, balance the European deficit for feed protein, and reduce energy utilization. All these potentials strongly comply with the current European tasks in agriculture.