Water requirements and crop coefficient for low-chill peach trees in subtropical climates

Two field experiments were carried out in Central Florida to determine the water requirements and crop coefficient (K_c) of young and adult low-chill peach trees grown in humid subtropical conditions. Peach trees of ‘TropicBeauty’ grafted on ‘Flordaguard’ were used. The first experiment was conducted from April 2016 to October 2018. Three weighing lysimeters were used to measure water losses every 30 min to obtain the daily actual evapotranspiration (ET_A) of young peach trees. K_c was calculated using the measured water losses and grass reference evapotranspiration (ET_o). K_c was plotted against the day of the year (DOY), a quadratic equation was fitted to the data, and the estimated K_c ranged from 0.22 to 0.67. The second experiment was conducted from September 2016 to August 2018. Soil volumetric water content was recorded every 10 min on the first 90 cm of the soil profile to calculate a soil water balance that could determine the crop evapotranspiration (ET_c). The average daily K_c was calculated by the ratio of ET_c to ET_o and plotted against DOY. A quadratic equation was fitted to the data, and the estimated K_c ranged from 0.32 to 0.69.