Under-trellis cover crop and planting density to achieve vine balance in a humid climate

The goal of our study was to improve Tannat Vitis vinifera L. grape and wine composition, by achieving vine balance in a humid climate. We tested under-trellis cover crops (UTCC) compared to a standard floor management of alleyway cover crops and under-vine herbicide. This strategy was tested in combination with variable planting density over three growing seasons in Southern Uruguay. Two factors were evaluated in a split plot design with five replicates. Treatments were, (1) UTCC (full cover of the vineyard soil with tall fescue (Festuca arundinacea Shreb)) versus conventional alleyway tall fescue with 1.0 m wide weed-free strips under the trellis, and (2) two spacings between vines in the row (0.8 vs 1.5 m). To avoid excessive vine water stress, supplemental irrigation was used during water deficit periods. Shoot growth rate, mid-day stem water potential, berry size and berry composition were monitored over the season as well as final yield, cluster and pruning weights. Results showed that UTCC reduced vegetative growth as expressed by pruning weight/m while closer PD resulted in greater vegetative growth parameters. UTCC reduced vine vegetative growth to recommended values of pruning weight per m of row under both plating densities. It also reduced berry size, cluster weight and bunch rot incidence as well as increased total soluble solids and anthocyanin concentration in grapes compared to the standard herbicide treatment. The use of UTCC with supplemental irrigation, showed promise for achieving vine balance in high vine capacity conditions.