Submitted to: Functional Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 10, 2011
Publication Date: May 2, 2011
Citation: Tarara, J.M., Perez-Pena, J.E., Schreiner, R.P., Keller, M., Smithyman, R.P. 2011. Net carbon exchange in grapevine canopies responds rapidly to timing and extent of regulated deficit irrigation. Functional Plant Biology. 38:386-400. Interpretive Summary: Grapevines grown in arid regions are commonly given less irrigation water than they need for maximal productivity, a technique known as regulated deficit irrigation or RDI. RDI is known to improve quality attributes in berries (because berry size is reduced and berries are exposed to more direct sunlight), but also reduces photosynthesis. The purpose of this research was to document if additional water deficit beyond the industry standard practice (even less water applied) either before or after the onset of berry ripening would further improve berry quality, or reduce photosynthesis too much thus harming the long term health and productivity of the vineyard. Photosynthesis of entire vines enclosed in custom-made chambers was measured at different plant growth stages over two growing seasons. Photosynthesis of vines subjected to additional water deficit was reduced by up to 45% compared to the industry standard RDI, but only during the time that the additional water deficit was being applied. Yield and quality parameters of the fruit were not altered by the additional deficits. Based on these findings, it can be concluded that less water can be applied than the standard RDI practice without altering fruit quality or causing long term damage to the vines.
Technical Abstract: Whole-canopy net CO2 exchange (NCEC) was measured at key stages during fruit development in grapevines (Vitis vinifera L.) managed under an industry standard practice of regulated deficit irrigation (RDI). A commercial vineyard was subjected to three regimens of RDI: 1) standard practice (RDIS), where 60 to 70% of estimated evapotranspiration for well-watered grapevines (ETc) was replaced weekly between fruit set and harvest; 2) early additional deficit (RDIE) where 30 to 35% of ETc was replaced weekly between fruit set and veraison (the onset of fruit ripening); and 3) late additional deficit (RDIL) where 30 to 35% of ETc was replaced weekly between veraison and harvest. When subjected to the additional deficit (NCEC) was as much as 45% (RDIE) and 33% (RDIL) less per day than in RDIS vines. The diurnal course of NCEC responded rapidly to RDI regimen and to individual irrigation applications. Relative differences in NCEC among RDI regimens were conserved at the leaf level (NCEL) but there was a weak association (r2=0.38) between concurrent NCEL and NCEC measurements. There were no differences among RDI regimens in berry mass at harvest despite the additional deficits having been imposed at discrete intervals thought to influence berry growth. The RDI regimen had no effect on yield per vine or fruit maturity indices, an artifact of low crop load. Summed between fruit set and harvest, about 40% less irrigation was applied to RDIE vines and about 20% less was applied to RDIL vines than to those managed under the local industry standard approach.