Effect of termination timing and incorporation of winter cover crop on the suppression of plant-parasitic nematodes and weeds

Abstract

Organic vegetable production faces challenges in managing plant-parasitic nematodes (PPNs) and weeds, as chemical options are prohibited. This study evaluated the effects of cover crop termination timing (90 and 120 days after planting, DAP) and cover crop incorporation, along with the application of an organic bioherbicide (Suppress EC), on PPN and weed suppression during the 2021 and 2022 winter seasons. The experiment utilized seven treatments of oilseed radish, oat, rye, mustard, a rye-oat mixture, and two fallows (with and without weeds), replicated five times per season for each termination timing and terminated at 90 and 120 DAP and incorporated into the soil. Results showed that termination timing significantly influenced PPN populations, with rye and oat reducing Meloidogyne incognita densities when terminated at 90 DAP, while mustard and radish increased nematode populations at 120 DAP. Incorporation of cover crops did not consistently enhance nematode suppression, especially in low-biomass scenarios. Weed suppression was more effective with later termination (120 DAP), particularly for rye and oat, which reduced weed biomass through shading and allelopathic effects. The combination of cover crops with bioherbicide further improved weed control, with significant reductions in corn spurry (Spergula arvensis) and cutleaf geranium (Geranium dissectum) compared to cover crops alone. However, the bioherbicide was less effective in suppressing weeds in mustard and radish plots. These findings highlight the importance of selecting appropriate cover crops and optimizing termination timing to manage PPNs and weeds. Integrating bioherbicides with cover crops offers a promising strategy for organic vegetable production, enhancing weed suppression and contributing to sustainable agroecosystems.