Application of Different Grassing Practices in Organic Viticulture and Their Effects on Soil Fertility

This study aims to evaluate the effects of two cover crop management practices on soil fertility. Key bioindicators, such as organic carbon content, were measured, along with the amount and activity of microbial biomass, which are mainly responsible for nutrient cycling. The conservative agricultural practices under study were either spontaneous meadows or annual overseeding with a barley (Hordeum vulgare) and faba bean (Vicia faba) mixture, both implemented for 4 consecutive years in the alleys of an organic vineyard. An untreated soil covered by a natural meadow for 30 years was used as the positive control. For each thesis, soil samples were collected at two depths (0–20 and 20–40 cm), and analyses were carried out on organic matter content and its fractions, as well as on relevant aspects of soil microbiota, such as microbial biomass carbon, microbial respiration, and soil enzyme activities. The effects of these practices on the quality and quantity of organic matter were evaluated by calculating the most commonly used humification indices and by assessing the metabolic and mineralisation quotients related to microbial biomass and activity. Over the relatively short treatment period, overseeding yielded better results than permanent grassland for organic matter content (plus 0.23%), overall hydrolytic activity (plus 17.62 µg g−1 h−1), and beta-glucosidase (plus 47.11 µg g−1 h−1) and beta-glucosaminidase (plus 11.56 µg p-NP g−1 h−1). However, several years of application are still needed to clearly assess the improvements and better compare different cover cropping techniques.