UC Riverside

Societal demands are increasing for safe crop production systems because of ecological and health risks of pesticides. Cover crops are an alternative to pesticides that may promote crop production. A three-year experiment was conducted to assess the multidisciplinary pest management potential of selected cover crops. The cover crops were planted during the summer and compared with a no-plant summer fallow system as a control treatment. The cropping treatments were assessed for concurrent suppression of weeds, parasitic nematodes, insect pests and their enhancement of beneficial organisms within the subsequent vegetable crop. The research was conducted at the South Coast Research and Extension Station in Irvine, California. Results indicated that the cover crops suppressed weed population densities and their biomass accumulation. Cover crop weed suppression was stronger against broadleaf weeds than grasses and intensity of suppression increased with increasing years of cover cropping rotations, indicating the buildup effect of the system. The cover crop provided stronger weed suppression when coupled with hand weeding, suggesting the importance of cover crops in an integrated weed management system. The cover crops also reduced the time required for supplemental hand weeding, indicating their potential economic benefits. While the off-season cover crops did not show any benefit for suppression of parasitic nematodes and insect pests in the subsequent vegetable crop, the system had significantly increased saprophytic nematode populations which play a beneficial role in improving soil nutrient status. The off-season cover crops also enhanced parasitoid populations and insect pest parasitization levels in the subsequent broccoli crop. At the same time, the cover crops preconditioned and improved soil and crop nutrition. Overall, the cover crops had combined effects on weed suppression, higher populations of beneficial organisms, enhanced soil and crop nutrition, and increased height, canopy growth, and leaf production of the vegetable crop. These combined effects resulted in higher productivity and marketable yields of broccoli compared to those grown on a summer fallow plot. Therefore the use of off-season cover-cropping rotations can provide multiple concurrent benefits to the productivity of vegetable crops.