Under-vine vegetation in vineyards: a case study considering soil hydrolytic enzyme activity, yield and grape quality in Austria

In vineyards, the under-vine area is managed to control vegetation growth and to reduce the competing effect of growing plants on vines and fruit development. Applied under-vine management methods are the application of herbicides, soil tillage or the growth of spontaneous vegetation or cover crops. These methods affect pedo-climatic conditions differentially as well as the soil biota and have, therefore, consequences on soil functions and ecosystem services. In the presented case study, the effects of five under-vine management methods on the activity of soil hydrolytic enzymes, the soil water content, vine photosynthetic activity, shoot pruning weight, grape yield and quality are investigated in a vineyard in Lower Austria over three consecutive seasons. Thereby, we hypothesise that a permanent under-vine vegetation cover, either mowed or without mowing, supports the soil microbial communities and soil functions in a way to enhance water and nutrients availability for vines which partly compensates for the competition of the growing vegetation. Our results confirm effects on the soil water balance, more specifically, a reduced soil water content in 11 -20 cm soil depths induced by a permanent vegetation cover as compared to herbicide application or soil tillage. Further consequences of permanent vegetation below vines were lower shoot pruning weights and lower berry weights, while total soluble solids and titratable acidity were not affected. The vine's photosynthetic activity, as well as the soil water content, were partly affected by treatments dependent on the precipitation ahead of the measurement. In parallel, the soil microbial activity was significantly enhanced by a permanent vegetation cover below the vines as compared to herbicide application, a trend which increased with the years of the project. In conclusion, permanent under-vine vegetation strongly promoted soil microbial activity without strong effects on shoot pruning weight, grape yield and quality. In the next step, a functional proof is necessary to characterise the interaction between soil microbial activity, soil water balance and vine nutrition and water status by using sensors for continuous measurements.