Complete vineyard floor cover crop to reduce grapevine susceptibility to bunch rot

摘要

Excessive vine growth not only negatively impacts fruit composition but also fosters bunch rot incidence. The goal of our study was to improveVitis vinifera(Tannat) grape and wine composition and decrease bunch rot incidence by achieving adequate vine vegetative growth in a humid climate. Our approach was to use under-trellis cover crops (UTCC) to limit vine water availability and reduce excessive vine growth. We tested UTCC consisting of full cover of the vineyard soil with red fescue (Festuca rubra) versus conventional alleyway red fescue with 1.0?m wide weed-free strips under the trellis (H). As excessive competition with grapevines remains the main reason for UTCC rejection, this strategy was tested in combination with two irrigation schedules—irrigation to avoid water restriction at bloom (Ir) vs. no early irrigation—and two nitrogen inputs (0 vs. 100?kg N ha?1) over three growing seasons in southern Uruguay. Treatments were arranged in a split-split-plot randomized block design with cover crop schemes as main plots, water availability as subplots and nitrogen inputs as sub-subplots. 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 the season. Even nitrogen input showed positive effects on grapevine vegetative growth in some cases, water availability at bloom was the key driver of vegetative growth. UTCC treatments increased grape soluble solids (TSS) in the last two out of three seasons and consistently increased anthocyanin concentration in grapes. Independent of vegetative growth, strong differences in bunch rot incidence were detected between H and UTCC treatments. Seasonal variations in water status and/or free amino nitrogen content of grapes may have a relevant impact on disease susceptibility at harvest.