Cover crop treatments differentially impact soil nematode communities including pathogenic genera

In the context of removal, or reduction in the use of plant protection products, cover crops, which are known to confer several benefits to soil, have been suggested as a potential agronomic intervention to manage soil-borne plant-parasitic nematodes. However, to date, cover crops have delivered a range of outcomes including nematode suppression, enhancement or no effect on target nematodes perhaps due to most studies being based on a single year with limited sampling (typically pre-sowing, post-harvest). In this study, over a 3-year period we sampled temporally (∼ every 3 weeks), to assess the effects of several cover crops on plant-parasitic nematodes and the wider nematode community. Using a constrained analysis of principal coordinates, two cover crop treatments Viterra Intensiv and Biofumigation Mix, had a greater association with plant-parasitic nematode genera whereas there was an absence of beneficial predatory genera associated with Viterra Intensiv and Oilseed radish cv. Defender. The remaining three cover crop treatments (Oilseed radish cv. Bento, a Vetch/Rye mixture and Phacelia) had no effect compared with the barley control. Not constraining the data by the barley control resulted in a significant month/crop interaction (p < 0.001) with clear temporal effects on the relative abundance of (Para)Trichodorus and Pratylenchus associated with several cover crops. The differential effects of cover crops in this study concurs with previous studies and highlights that the use of cover crops to manage plant-parasitic nematodes has variable outcomes. Thus, more research is required to fully understand whether cover crops are a viable efficacious alternative to manage plant-parasitic nematodes.