Thermal remote sensing measurements as a tool to monitor evaporation/transpiration in vineyards

An accurate estimation of crop evapotranspiration (ETc), and its partition into both components, soil evaporation (E) and canopy transpiration (T), is known to be critical for a more effective irrigation scheduling of row-crops in arid and semi-arid environments. Vineyards are the best example in Mediterranean countries. In a recent experiment based on lysimeter measurements, we tested the potential of the two-source energy balance modeling using thermal radiometry to derive isolated T. The aim of this work is to improve our understanding of the E/T partition by establishing a separate energy balance for soil and canopy components. Two similar experiments were conducted using different vine cultivars, at separate locations and different environments in Spain: Palma de Mallorca (June-October, 2012) and Barrax, Albacete (June-October, 2013). A set of thermal-infrared radiometers were assembled pointing directly to the plants and the soil between rows. Measurements of the four components of the net radiation over the canopy and soil heat fluxes, as well as meteorological variables and biophysical parameters were all collected and stored every 15-min. Hourly and daily averages were then computed and analyzed. An average daily ETc value of 3.1 mm day^-1 was observed in both sites. Interrow soil evaporation reached as much as 40 and 30% of the total ETc in Mallorca and Barrax, respectively. These results provide a first insight into the partition E/T and show the potential of the vine thermal characterization with this aim.