Tomato irrigation scheduling improved by using percent canopy cover and crop developmental stage

Abstract

The aim of this study was to evaluate whether it is possible to conserve water and improve yield using canopy cover in order to adjust the amount of water needed for drip-irrigated tomatoes. The experiments were carried out using field-grown tomatoes (Lycopercion esculentum cv. Dual Large, F1) in Central Anatolia, Turkey from 2003 to 2005. The experimental design used split-plots in randomised blocks with 3 replications. The main plots in this study were: I1, constant Class A pan evaporation (Ep) (i.e. K = 1.0) throughout the irrigation season; I2, varying Ep proportion according to crop development stage (i.e. planting time to flowering stage 0.50; flowering stage to first harvesting 1.0; and first harvest to last harvest 0.75. In subplots, wetted area percentages or canopy cover were used. In K1, the wetted area percentage measured 90% of the experimental site. In K2, the wetted area percentage varied depending on the canopy cover. In K3, the percentage of wetted area was set to a value of 65% throughout the irrigation season. The maximum yield of 134.8 t/ha was obtained with the I2K2 treatment, with a seasonal irrigation requirement of 515 mm. A tomato yield of 122.8 t/ha was obtained under conditions of 552 mm seasonal irrigation water applied using the I1K2 treatment. Although 37 mm less water was used in the I2K2 treatment, the yield obtained from that treatment was higher by 12.0 t/ha than the I1K2 treatment. In addition, the yield with all other treatments was lower than the I2K2 treatment. Similarly, the maximum irrigation water-use efficiency (IWUE) of 26.2 kg/m3 was obtained with the I2K2 treatment. Thus, use of different coefficients of Ep varying with crop growth stages and percentage of canopy cover to estimate irrigation water requirement (i.e. irrigation scheduling) maximised the yield of tomatoes and improved the IWUE.