Crucifer-legume cover crop mixtures for biocontrol: Toward a new multi-service paradigm

Multi-service cover crops grown during the fallow period between two main cash crops are a tool to support sustainable crop production. Crucifer-legume mixtures may provide improved multi-ecosystem services compared to sole cover crops, but trade-offs between the known crucifer biocontrol potential and N cycling benefits of legumes are uncertain. We review suppressive effects of crucifers as sole crops and in mixtures with legumes for a wide range of pathogenic and beneficial organisms to compare the services and potential disservices of the strategies. We conclude that biocontrol services of crucifer sole crops could be largely maintained in crucifer-legume mixtures while improving nutrient services, and reducing potential disservices. The lack of comprehensive multi-disciplinary field studies that investigate the multi-service paradigm limit our current understanding of the trade-offs between services, but reveal fruitful research opportunities. We emphasize 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.