Complete vineyard floor cover crop for sustainable bunch rot management in a humid climate

Abstract

Benefits of under-trellis cover crops (UTCC) have been reported. Our goal was to evaluate the UTCC, as tool to restrict vegetative growth of Vitis vinifera cv. Tannat grapevines in a humid environment. The UTCC treatment consisted of the full cover of the vineyard soil with red fescue (Festuca rubra). Treatments were arranged in a split-split-plot randomized block design with cover crop schemes as main plots (UTCC vs. under-vine herbicide (H)), water availability as subplots (irrigation to avoid water restriction at bloom (Irr) vs. no early irrigation) and nitrogen inputs as sub-subplots (0 vs 100 UN/ha). Shoot growth rate, mid-day stem water potential (Ψstem), berry size and berry composition were monitored over the season as well as final yield, cluster and pruning weights. UTCC significantly reduced vine vegetative growth, while no significant differences were detected between H and UTCC when irrigation took place early in season. Even nitrogen input showed positive effects on grapevine vegetative growth. Water availability at bloom was the key driver of bud fertility, berry number per bunch and vegetative growth. UTCC treatments increased grape soluble solids (TSS) the last two seasons and consistently increased anthocyanin concentration in grapes. Strong differences between H and UTCC treatments were detected concerning bunch rot incidence independently from vegetative growth. Seasonal variations in water status observed may have a relevant impact on disease susceptibility at harvest.