Effects of within-block canopy cover variability on water use efficiency of grapevines in the Sunraysia irrigation region, Australia

• Published in: Agricultural water management Vol. 211; pp. 10 - 15
• Main Authors: McClymont, L., Goodwin, I., Whitfield, D.M., O’Connell, M.G.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2019
• Subjects: Crop water supply; Evapotranspiration; Vineyard; Water loss; Yield penalty; Crop water supply; Water loss; Vineyard; Yield penalty; Evapotranspiration
• ISSN: 0378-3774; 1873-2283
• DOI: 10.1016/j.agwat.2018.09.028

•Analysis of 74 vineyards showed substantial variation in canopy cover and estimated evapotranspiration.•Modelled vineyard water loss was typically 25% when irrigated to match maximum vine evapotranspiration.•Modelled water loss was reduced to less than 10% when irrigated to match block mean canopy cover with only a 5% loss in potential yield.•Gains in water use efficiency can be made by improving canopy cover uniformity or dividing blocks into smaller irrigation management units. Irrigation methods commonly aim to match water supply to water requirement so that production outcomes are optimised. Grapevine water requirement estimates can be improved by adjusting crop coefficients for canopy cover (CC). Analysis of aerial images of 74 vineyard blocks revealed substantial ranges in CC between and within blocks. Within block variation compromises the ability to match water supply to water requirement at the sub-block scale. Water losses (WL) and yield penalties (YP) were modelled under two irrigation scenarios based on relationships between CC, water use and yield. These irrigation strategies aimed to match mean water use or maximum water use of grapevines within each block. While WL and YP are driven by CC variability, WL and YP were affected by CC and the irrigation strategy. Predicted WL under irrigation to match maximum ETc were typically 25% of water supply, whereas irrigating to match mean ETc reduced WL to less than 10% of water supply. Irrigating to match mean ETc penalised the grower, on average, 5% of potential yield. The model used in this study provides a basis for assessing impacts of CC variability in vineyards and evaluating options for improving water use efficiency at the block and sub-block scale.