Multi-service cover crops: towards a new paradigm for biocontrol and soil fertility enhancement
Résumé
Usually grown between two cash crops in an annual rotation, cover crops can increase species diversity and provide a number of ecosystem-services as an efficient tool to support sustainable agricultural production based on the principles of agroecology. Brassicaceae or crucifers can
generate glucosinolate-related biocidal effects both during the growing period when hydrolysis products such as isothiocynalates are released in the rhizosphere around the growing roots or when tissue disruption occurs following cover crop termination and incorporation. The new paradigm of multi-service cover crop has been proposed by Couedel et al. (2019) to capture these multiple benefits and emphasise the need to refocus cover crop biocontrol research from a largely “pesticide” paradigm, targeting maximum production of bioactive compounds by sole crucifer cover crops, to a multi-service paradigm in which selected crucifer-legume mixtures may offer promise in the quest for the sustainable intensification of agriculture. By taking a wider systems approach, beyond pest management, and then by using a multi-service paradigm, cover crops may enhance the physical, chemical and biological fertility of the soil. Understanding the trade-offs between abiotic and biotic services within a system approach is now key to assess services and disservices provided by cover crop mixtures. Now, the potential provision of multi-services depends on species or mixture of species, the management of the cover crop, the pedo-climatic conditions and the cash crop sequence involved. We showed that the biocontrol services of crucifer sole crops could be largely maintained in crucifer-legume mixtures while improving nutrient services and C sequestration, and reducing potential disservices, such as water and nitrogen pre-emptive negative effects for the following cash crop. However, multi-service cover crop mixtures cannot be seen as a stand-alone solution to manage pests and pathogens, but it is likely that adequate levels of control will require combinations with other pest management tactics.