Can different green manure fertilizations affect the vine balance and grape quality? First evidence of multi-year study

Abstract

In the context of sustainable viticulture that implements organic practices to maintain soil fertility, green manuring plays a crucial role due to its ability to stock carbon and nitrogen in soil while supporting biodiversity. Green manure alone is not sufficient to restock the nutrients removed with harvested grapes. Over time, this can lead to a depletion of available K in the soil and a tendency towards an imbalance in the vegetative and productive parameters of the vineyard. To assess the recovery of removed elements and the enhancement of vineyard fertility, we conducted a comparative analysis of various fertilization strategies in a Pinot blanc vineyard (clone LB18, pergola trentina trellis system).

The treatments included unfertilized green manure (GM), GM fertilized with digestate from anaerobic digestion of cattle manure (GMD), compost from digestate obtained from anaerobic digestion of OFMSW (GMC) and with mineral fertilizer (GMM). Input was standardized at 72 units of N ha⁻¹. The cover crop biomass was sampled at mowing, and C, N, P, K, and Mg, as well as the dry matter production, were analyzed. At grape’s technological maturity yield, average bunches weight, composition of the berries (C, N, P, K, Mg) and musts (Brix, pH, total acidity, YAN, etc.) were determined. In late autumn, pruning wood weight was measured. The biomass analysis of the cover crop revealed that the GMM had significantly higher values for dry matter, C, N, P, and K. The C/N was significantly greater in the GMD. No significant differences were observed among the treatments in terms of yield, average weight of bunches and pruning wood, and Ravaz index. The analysis of the berries revealed the higher K content in the GMM, while no significant differences were found for C, N, P and Mg. The chemical parameters of the musts did not reveal any significant differences. In the year of fertilization, the results show that K is the distinguishing element among treatments, both in the cover crop and in the berries. The K input in mineral form is partially incorporated into the cover crop’s biomass and transferred to the berries. This result suggests a balance between the cover crop’s absorption and the vine’s nutritional requirements. In addition to the parameters mentioned, the dynamics of soil and leaf elements, and wine quality have also been analyzed. The ongoing multi-year study will provide further insights into the medium-long term effects of fertilization.