Influence of vineyard floor management practices on grapevine vegetative growth, yield, and fruit composition

The viticultural effects of sward competition with vines for water and nutrients, indirectly resulting from reduced herbicide use under a sustainable production system, are well established in cooler, more humid areas but are less well understood in warm and dry areas. Three groundcover treatments-standard industry practice of herbicidetreated undervine strips, bare soil maintained with herbicides, and complete floor cover (no herbicides)-were applied in two Chardonnay vineyards, one in a hot dry climate, the other in a mild climate. Increasing floor cover decreased early-season soil moisture and petiole nutrient status and strongly reduced vine vegetative growth. After three experimental years, grape yield also became limited. Large treatment differences in vegetative growth, canopy structure, and yield contributed to differences in berry weight and composition. Vine response to floor covers was less pronounced under mild climatic conditions compared to hot and dry conditions. Total or partial floor cover is a powerful tool for controlling vegetative growth of grapevines. However, under hot and dry conditions, competition for water and nutrients, particularly if it occurs at sensitive stages (such as bloom and berry set) can lead to a substantial decrease in yield and vine capacity.