Remote sensing model to evaluate the spatial variability of vineyard water requirements

The main agricultural areas of Chile will face a significant reduction of rainfall (between 20-40%) due to the global climate change. Also, Chile is periodically affected by the climatic phenomenon of “La Niña” (ENSO), which has produced important droughts and economical losses in most of agricultural areas. Under these conditions, sophisticated irrigation water management will be required to optimize water productivity (kg m^-3) and to maintain sufficient levels of yield and wine quality. In this regard, the objective of this paper is to evaluate the METRIC (mapping evapotranspiration at high resolution with internalized calibration) model to generate maps with spatial distribution of crop coefficients (Kc) and actual evapotranspiration (ET) of a vineyard (1106 ha) using satellite images. Results of this study indicated that METRIC model could be a useful tool to evaluate the spatial variability of ET and Kc with errors less than 11%. Major disagreements were observed during October and November when soil surface between rows was wet and presented cover crop (weeds). For the vineyard, values of Kc and ET for the overhead trellis (OT) system ranged between 0.75-0.90 and 5.8-7.0 mm day^-1 while those for the vertical shoot positioned (VSP) system were between 0.30-0.45 and 2.0-3.3 mm day^-1, respectively. Finally, seasonal ET ranged between 320 and 800 mm season^-1 where the highest and lowest values were associated with the OT and VSP systems, respectively.