Effects of crop forcing and water availability on yield and biomass partitioning in Tempranillo vines

Much recent grapevine research has focused on management techniques that allow grape harvesting under cooler conditions. Crop forcing, a summer pruning technique that ‘forces’ the vine to start a new cycle, can delay the harvest date by several weeks. However, information on how crop forcing affects root biomass production is currently limited. A two-year trial was conducted using potted vines to examine how crop forcing, and water availability might influence biomass partitioning. Six irrigation treatments were applied to forced (F) vines: deficit irrigation before forcing (F-PreF); deficit irrigation from veraison to harvest (F-V); a combination of these two treatments (F-PreF-V); deficit irrigation from veraison to harvest with no irrigation after harvest (F-V-PH); deficit irrigation throughout the growing season (F-DI); and irrigation at 100% of crop evapotranspiration (F-FI). The results were compared with unforced (UF) treatments: fully irrigated (UF-FI) and deficit irrigation throughout the growing season (UF-DI). The F-FI treatment reduced water use by 34% compared to the UF-FI treatment. Although the F treatments resulted in a significant yield reduction (85%), they increased the allocation of biomass to vegetative organs, and the crop forcing technique did not negatively affect root biomass production. Both UF-DI and F-DI treatments reduced root production compared to their respective FI treatments (UF-FI and F-FI). Furthermore, new root biomass was positively correlated with vine water use and total vine photosynthetic capacity when only F treatments were analysed.