Shifts in Nematode Foodweb Structure and Nutrient Cycling Following Sustainable Soil Management in a California Vineyard.

Nematodes are an important part of soil ecosystems, as they liberate otherwise unavailable plant nutrients via consumption of soil microbes. Nematode genera also occupy a wide range of trophic levels and life-history strategies, so their community structure is used to glean information about overall soil food web structure and soil health. Established nematode community indices can be used to extrapolate information about soil fertility, nutrient enrichment, and environmental quality. The goal of this study was to assess soil health via characterization of nematode community indices in vineyard soils under differing management practices. The following 8 soil management strategies were implemented: high or low water-use cover crops, no cover crop, herbicide application compared to no herbicide, and organic or synthetic fertilizer application, compared to no fertilizer. In 2016, 6 replicates for each of the 8 treatments were established in a Pinot Noir vineyard following a randomized block design in San Luis Obispo, California. Soil samples (20 cm depth) were collected during the 2017 season at budbreak, bloom, véraison and harvest. Nematodes were extracted via sieving and sucrose centrifugation of field moist samples. Nematodes were quantified and classified based on feeding habits and life history strategy to calculate maturity, enrichment, structure and channel indices. Changes in plant-available N and organic N and C concentrations were measured in the soil samples as biochemical indicators of soil health. Vine and wine quality were also evaluated to correlate changes in soil health with crop yield and quality. Nematode foodweb structure was responsive to soil management practices, and seasonal changes were also observed over time. However differences in vine development between the treatments were not significant. Overall, nematodes proved to be good indicators of soil health. The results of this study will contribute to future management of soil health by the wine industry.