On-farm monitoring of grapevine water and nitrogen status in relation to different soil management practices in Valais, Switzerland

Abstract

In response to increasing societal demands for environmentally-friendly viticulture, winegrowers are adapting their cultivation techniques, particularly by reducing the use of herbicides. One such technique involves the implementation of grass cover in vineyards, which can serve as an effective tool for limiting herbicide usage. However, in the Valais region of Switzerland—where vineyards are often located on steep slopes and face dry pedoclimatic conditions with an average annual rainfall of 580 mm—this practice can be challenging to implement. To investigate the impact of grass cover in vineyards, an on-farm network was established in Valais. This network includes over 90 vineyard plots planted with cv. Pinot noir and cv. Chasselas. Cultivation methods are determined by the individual winegrowers and are representative of common practices in the region. Various soil management techniques are employed across the network, including spontaneous grass cover vs sown cover crops, inter-row cover cropping vs total cover cropping, and bare soil management. The primary goal of this network is to evaluate current practices and derive conclusions on grassing techniques suitable for the conditions of Valais. Over three vintages (2022-2024), several physiological and agronomical parameters were assessed to observe vine behavior, including vine vigor, yield components, mineral nutrition, and must composition (with a focus on yeast assimilable nitrogen). Additionally, the water status of the vines was monitored using two indicators: predawn leaf water potential and delta C13 in must sugars.

Our results indicate that, depending on the specific conditions (including vintages and terroirs), the competition between plant cover and vines for access to water and nutrients (particularly nitrogen content in berries) can be significant. This competition may lead to negative impacts on both the quantity and quality of the harvest. Therefore, the use and intensity of grass cover must be carefully adapted to the soil conditions of each plot to prevent excessive competition.