Evapotranspiration of grapevine trained to a gable trellis system under netting and black plastic mulching

The evapotranspiration (ET (c)) of a table grape vineyard (Vitis vinifera, cv. Red Globe) trained to a gable trellis under netting and black plastic mulching was determined under semiarid conditions in the central Ebro River Valley during 2007 and 2008. The netting was made of high-density polyethylene (pores of 12 mm(2)) and was placed just above the ground canopy about 2.2 m above soil surface. Black plastic mulching was used to minimize soil evaporation. The surface renewal method was used to obtain values of sensible heat flux (H) from high-frequency temperature readings. Later, latent heat flux (LE) values were obtained by solving the energy balance equation. For the May-October period, seasonal ET (c) was about 843 mm in 2007 and 787 mm in 2008. The experimental weekly crop coefficients (K (cexp)) fluctuated between 0.64 and 1.2. These values represent crop coefficients adjusted to take into account the reduction in ET (c) caused by the netting and the black plastic mulching. Average K (cexp) values during mid- and end-season stages were 0.79 and 0.98, respectively. End-season K (cexp) was higher due to combination of factors related to the precipitation and low ET (o) conditions that are typical in this region during fall. Estimated crop coefficients using the Allen et al. (1998) approach adjusting for the effects of the netting and black plastic mulching (K (cFAO)) showed a good agreement with the experimental K (cexp) values.