Intercropping, an agroecological practice consisting in growing distinct crops on the same plot at the same time, may play a role in the transition to sustainable agriculture thanks to its benefits, e.g. higher yield, lesser use of pesticides. In recent years, it has experienced a particular boom in market gardening and there are now countless mainstream market gardening books dealing with it. However, its use by professional market gardeners remains low. The most likely reason is that intercropping is more complex than the image conveyed by these books and very little objective data is available to help market gardeners in its relevant implementation.
This PhD thesis tackles the issue of intercropping in market gardening with the aim of providing market gardeners with knowledge and reliable information enlightening management choices. We begin by listing the interactions observed in intercropping, both between the associated crops and with their environment, and present them as networks. We then investigate the prediction of intercropping outcome based on complementarity principles by comparing the results of various intercrops in on-field trials. We show the importance of the difference in sowing date, growth dynamics and maximum soil coverage between crops in the determination of yield gain and yield gain asymmetry in intercrops. Finally, we address the issue of yield inter-site variability by comparing the growth of three intercrops in different farms, using participatory trials. We explain our methodology and show the consistency of intercrops relative yield in a range of environmental conditions and crop management practices.
Our approach is purposely exploratory. This thesis paves the way for the scientific study of intercropping in market gardening and highlights some key points for the use of intercropping by market gardeners.
The PhD thesis is available here.
