Determining grapevine water use under different sustainable agronomic practices using METRIC-UAV surface energy balance model

Because of climate change and the scarce availability of natural resources there is a need to develop sustainable intensification strategies intended for optimizing water use in vineyards. In this study, water regime, fertilization and soil management practices were assessed in terms of vineyard water use, by evaluating the inter-row and crop line evapotranspiration (ET) components using the Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC) model in combination with unmanned aerial vehicle multispectral and thermal images taken on five dates throughout the growing season. The application of the METRIC-UAV using high-resolution imagery was proven as a useful tool for evaluating the effects of sustainable intensification strategies on water use of crops where vegetation does not completely cover the soil, identifying the most efficient site-specific strategies for water conservation purposes. Moreover, METRIC-UAV allowed evaluating separately their effects on the inter-row and the crop line. Among the assessed sustainable intensification strategies, the application of mulching provided the highest water savings (- 28%) when compared to traditional soil tillage management, reducing inter-row soil evaporation by 63%, while increasing crop-line ET by 14%. In spite of this, the mulching application did not affect yield, but significantly enhanced water use efficiency (WUE) in terms of grape yield compared to tillage. The adoption of deficit irrigation (DI) strategies did not result in vine water stress that was severe enough to significantly affect crop line ET when compared with fully irrigated (FI) vines. Both DI and FI strategies increased vine water use by 18% and 27%, respectively, as compared to the rainfed regime, with no differences found in the inter-row water consumption. DI and FI, in turn, significantly increased yield as compared to rainfed crops, leading to significant improvements in WUE. In the short term, the application of supplemental inorganic fertilizers did not modify either the vineyard water use or vine performance.