Cover Crops and Carbon Stocks: How Under-vine Management Influences SOC Inputs and Turnover in Two Vineyards

There is a growing awareness surrounding the importance of maintaining and increasing soil organic carbon (SOC, henceforth) stocks in vineyard systems. Increasing SOC positively influences numerous soil properties and has the added advantage of removing atmospheric CO, thereby helping to mitigate the effects of climate change. Cover crops have long been used to influence soil properties in vineyard mid-rows, including increasing SOC content. Few studies, however, have quantified cover crop influence on SOC stocks and composition in the under-vine area, owing to a general reluctance to adopt under-vine cover crop management. This research aims to quantify SOC stocks and dissolved organic carbon (DOC) in soils from four treatments of under-vine management practice including two cover crop combinations, a straw mulch and herbicide-managed control across two vineyard sites established in 2014. We sampled soils under-vine to depths of 0-30 cm (stratified; 0-10 cm and 10-30 cm) and quantified both SOC concentrations and bulk density to ascertain SOC stocks. Further to this, we quantified water extractable organic carbon (WEOC) as a measure of the labile carbon stock, and measured heterotrophic respiration in a laboratory incubation as an indication of SOC turnover. We found that cover crop-managed soil under-vine sequesters up to 23% more soil organic carbon (SOC) as the traditional, herbicide practice over a five-year period of growth. Microbial activity increased by more than double in cover crop soils, owing to an increase in DOC and that there is evidence for more resistant C in cover crop soils. These results suggest that cover crop management under-vine is a viable solution to increase SOC stocks within vineyard systems. Taken together, the results of this study indicate that a shift from bare earth to cover crops in the under-vine region has the potential to sequester carbon in vineyard soils.