Estimating Actual Transpiration of Apple Trees Based on Infrared Thermometry

Abstract

AbstractA method was developed based on the radiative properties and energy budget of a single apple leaf to calculate the actual transpiration (T) of apple trees. The model uses canopy temperature (Tc), air temperature (Ta) measured in the orchard, and other meteorological data from a local weather station as inputs. The model was applied to two scenarios, as follows: (1) well-watered, young Fuji apple trees in the 2007 and 2008 growing seasons; and (2) older apple trees, bearing little fruit in the 2013 growing season. Simulated transpiration rates at both scenarios were compared with Penman-Monteith (PM) model predictions corrected by regionally adjusted crop coefficients, i.e., values of ETc. In 2007 and 2008, a linear regression analysis of the relationship between daily mean transpiration (Tavg) and ETc revealed that they better agreed on warm and dry days (correlation coefficient R2=0.57, slope=1.16, and intercept=0.4) than during cold and humid periods (R2=0.48, slope=0.69, and intercept=2.3). Com...