Soil fertility and agronomic performance of green manure in vineyard

The practice of green manure has numerous positive effects on soil fertility in vineyard. It improves soil structure, reduces erosion, acts on the nitrogen and organic matter content, temporarily immobilises nutrients and releases them gradually. Moreover, green manure promotes the biodiversity of the entire vineyard system. The aim of this research was to study, over a medium-term period, the effect of a balanced green manure mixture on soil organic matter (SOM), soil nitrogen (N) and vineyard agronomic performance. The trial was conducted starting in 2011 in a Pinot blanc vineyard in Trentino, organised in plots under integrated (mineral fertilisation on the row) and organic management (green manure on alternate inter-rows), named MIN and GM respectively. SOM and total N were determined using the Dumas method. Organic carbon (OC) fractions with different degrees of stability were measured using TOC and CN analysers after acid hydrolysis in H2SO4. Yield was determined at technological ripeness as kg per vine and vine growth was evaluated in winter as pruning wood (kg/vine). The SOM content only in the GM thesis showed an increasing trend over the ten years of study. The OC labile and stable fractions grew statistically in the thesis with green manure seven years after the start of the trial, in contrast to the MIN thesis. Total N in GM also showed a significant increase in the last two years of the study compared to the first years, demonstrating that the mineral N fixed by N-fixing bacteria in Fabaceae was converted into soil organic N. Vine yield was comparable between the theses over the study period. The relationship between yield and pruning woods showed a deficit in the woody biomass. In this study, green manure was shown to enhance carbon sequestration and improve soil fertility. While ensuring an adequate yield, the vegetative results indicated the need in the medium to long term to integrate nutrients not supplied by green manure, to maintain a good vegetative-productive ratio.