Determining the effect of different cover crops on nematode communities in vegetable production

Abstract

Agricultural soil environments contain different types of nematodes, part of several trophic levels that aid in balancing the soil food web. Beneficial free-living nematodes (FLNs) consist of bacterivores, fungivores, predators and omnivores that help in the mineralization of the soil and the top-down control of damaging plant-parasitic nematodes (PPNs). Conversely, PPNs feed directly on plant roots and cause $125 billion in worldwide crop losses annually, making them a plant pathogen of great concern for growers. Farmers have started to implement the use of cover crops in agricultural systems for the protection and enrichment of soil but research on how different covers affect nematode populations is lacking and in demand. This study aims to determine the effect of legume and grass cover crops, cow pea and pearl millet, as well as their mixture on the abundance and diversity of FLN and PPN populations. Soil samples were taken prior to, during, and after cover crop implementation to analyze nematode communities using morphological and DNA metabarcoding techniques. Results showed that the implementation of cow pea and pearl millet covers as well as their mixture in a spinach agricultural system led to the control of PPNs and the proliferation of FLN communities. Specifically, we found that the mixture of both cover crops and the use of pearl millet as a single species generated healthier nematode populations with significantly less PPNs and more FLNs when compared to the control and fallow plot treatments using both nematode identification methods. However, the choice of cover crop to implement by growers should be based on specific soil health needs to promote a healthy soil and nematode population. Ultimately, understanding how different cover crops impact nematode populations can inform sustainable agricultural management practices. By strategically selecting legume and grass cover crops, farmers can optimize soil health, reduce crop losses caused by PPNs, and promote a balanced soil ecosystem to improve crop productivity.