Under-trellis cover crop and deficit irrigation to control vegetative vine growth in a humid climate

Abstract

The goal of our study was to improve Tannat grapes and wine composition, by achieving vine balance. We propose a change in the current Uruguayan grape-growing paradigm that accepts unpredictable periods of water deficit or excess in non-irrigated vineyards applying herbicides to eliminate weeds competition. We used an under-trellis cover crop (UTCC) to limit vine water availability, reduce vine growth rate and final canopy size. However, to avoid excessive vine water stress due to the UTCC competition, irrigation was used during water deficit periods. The experiment was conducted over two consecutive growing seasons from 2011 to 2013, in two experimental vineyards located in Southern Uruguay (34º S 56º W). Treatments were: UTCC (full cover of the vineyard soil with tall fescue) versus conventional alleyway tall fescue with 1.0 m wide weed-free strip under the trellis. Deficit drip irrigation was provided at mid-day stem water potential (SWP) thresholds of -0.9 MPa early and -1.1 MPa later in season. Shoot growth rate, SWP, berry size and berry composition (Brix, organic acids, total anthocyanin) were monitored over the season as well as final yield, cluster and pruning weights. Preliminary results showed that UTCC regulated vine vegetative growth and final canopy size, reduced berry size, cluster weight and bunch-rot incidence as well as increased Brix and anthocyanin concentration in grapes in both experimental sites. The use of UTCC, supplemented with deficit irrigation, shows promise for achieving vine balance in high- capacity conditions.