Estimating Transpiration and Soil Evaporation of Vineyards from the Fraction of Ground Cover and Crop Height - Application to 'Albari?o' Vineyards of Galicia

摘要

This study aims at quantifying crop transpiration and soil evaporation of traditional 'Albari?o' vineyards with active ground cover and modelling the time evolution of the available soil water content. The experimental study developed during three crop seasons, 2007-2009, in a traditional "semi-trellised" vineyard of V. vinifera 'Albari?o' in Galicia, northwest Spain. The field experiment had four treatments: two sites rainfed, drip irrigation and subsurface drip irrigation. Field observations included crop phenology, soil water content, irrigation and fertigation, weather data and the fraction of ground cover. The SimDualKc model was applied to the observed data. It adopts the dual crop coefficient approach, i.e., K_(cb) relative to crop transpiration and Ke to describe soil evaporation, thus allowing a separate estimation of transpiration and evaporation. The Kcb values were adjusted to crop density using a density coefficient (K_d), which depends upon the effective fraction of ground covered or shaded by vegetation (fc_(eff)) and the mean average height of vine plants (h), which is a methodology not yet applied to vineyards' experiments. The K_e values were estimated from a daily water balance of the soil evaporation layer. The SIMDualKc model was calibrated and validated with the experimental data by comparing model simulations with TDR observed soil water contents data. Model fitting was assessed with a regression forced to the origin. The regression coefficients for the various years and experiments range 0.96 to 1.06 and the coefficients of determination are larger than 0.92. These results show that both the adopted density coefficient methodology and the model are appropriate to estimate transpiration and evaporation in a trellised vineyard with active ground cover. Crop transpiration is nearly 70% of crop évapotranspiration. Following this application, improved water management issues for irrigation of vineyards will be searched using the model.