Evaluating the effect of different management practices on vineyard evapotranspiration by using remote sensing-based energy balance models

Several strategies have been developed for improving water use efficiency in agriculture. The effectiveness of such strategies is commonly assessed using classical methods based on ground measurements. However, most of these are high-cost, time-consuming and invasive methods that may not reflect the high crop variability, especially in woody crops due to its punctual nature. Alternatively, remote sensing has proved to be an accurate technology for determining crop water requirements, which allows covering large spatial extents capturing the spatial variability within the crop in a non-invasive, time and cost-effective way. The main objective of the study was to evaluate the performance of four different management practices applied to a vineyard located in Valencia (Spain) through their influence on crop evapotranspiration (ETc). These factors include: i) irrigation strategy, with rainfed, full and deficit irrigation; ii) type of fertilizer, organic versus inorganic; iii) trellis inclination, comparing west, vertical, and east inclinations; and iv) presence or absence of mulching. ETc was determined using the METRIC energy balance model with high-resolution imagery acquired from a drone with a multispectral and a thermal sensor onboard. The obtained results showed that evapotranspiration of west-tilted and east-tilted vineyards was 3.8% more and 4.7% less than vertical vineyards, respectively. Regarding irrigation strategies, both deficit irrigation and rainfed treatment provide less ETc than full irrigation treatment, with reductions of 4.6 and 6.7%, respectively. Also, the incorporation of mulching decreased the ETc, by 25.9-27.1% mainly due to a reduction in the soil evaporation component. Contrarily, no significant differences in ETc were observed when using organic or inorganic fertilizer. In conclusion, the METRIC energy balance model proved to be suitable for identifying the effect that different management practices have on ETc, being the use of mulching the strategy that could result in larger water saving.