Water Requirement of Arabica Coffee under Different Shade Conditions during the Dry Season

Abstract

This study investigated the water use of Arabica coffee (Coffea arabica L.) under different shading environments during the dry season. The experiment was conducted from February 22 to 28, 2024, at Maejo University. Four 3-year-old Arabica coffee trees were each planted in a 30-liter pot and assigned to one of two treatments: under a 50% shade net or in an open field (full sunlight), with two plants per treatment. All trees were at the floral bud stage, which is known to respond strongly to irrigation. Sap flow sensors were installed to measure actual plant water use (ETc), and weather data were collected from an automatic weather station to calculate reference evapotranspiration (ETo) and the daily crop coefficient (Kc). The objectives were: 1) to evaluate the water use of arabica coffee under different shading conditions using the sap flow technique; 2) to determine crop coefficients (Kc) for accurate irrigation scheduling during the dry season; and 3) to assess the relationships between vapor pressure deficit (VPD) with both ETo and ETc. Results showed that open-field plants had higher average ETc (2.15 L plant^-1 day^-1) and Kc (1.39) compared to shaded plants (ETc = 1.06 L plant^-1 day^-1, Kc = 0.61). The coefficient of determination (R²) between VPD and ETo was 0.934, while the R² between VPD and ETc was 0.526, reflecting the plant’s physiological regulation of transpiration under varying microclimate conditions. These findings provide a basis for more precise irrigation planning in coffee cultivation, especially during flowering induction in dry periods.