WATER PRODUCTIVITY OF IRRIGATED TOMATOES IN EASTERN CANADA BASED ON AQUACROP SIMULATIONS.

Methodologies to predict crop water requirements in arid and semi-arid regions are well known. Humid regions such as eastern Canada pose a challenge because irrigation is normally only required for short periods during the growing season to supplement rainfall. This study assessed the capability of the AquaCrop model to simulate the effects of different irrigation regimes on field-grown tomatoes (Solanum lycopersicum L.) in the humid region of eastern Canada. The experimental study was conducted at the Horticultural Research station of McGill University, Quebec, Canada. There were three irrigation treatments in 2017 and in 2019, that were based on the % depletion of available water content (AWC). The AquaCrop model was calibrated and verified with the 2017 and 2019 field data, respectively. The verified model was used to predict irrigation water requirements and fruit yield for the driest year (1993) and the average rainfall year (2001) of a 35-year historic weather dataset from 1986 to 2000, for three different soil types (silty clay, sandy loam, and heavy clay) under four irrigation regimes. Model performance was greatly improved when the seasonal harvest index (HI) measured from experimental data was used instead of the default model HI values. AquaCrop was suitable for estimating dry yield and total biomass with RMSE = 0.57 ton ha-1 and 0.89 ton ha-1, respectively, in the calibration phase, and RMSE = 0.28 ton ha-1 and 0.01 ton ha-1 for dry yield and total biomass, respectively, in the verification phase. These results indicate a very high accuracy of AquaCrop to estimate total above ground biomass and fruit yield in humid regions with seasonally adjusted HI values. The predictions showed that maintaining AWC depletion below 25% resulted in no significant decrease in crop yield and biomass, making it an optimum water management guideline for irrigated tomato production in Quebec. The findings of this study are useful to crop growers and water resource managers in eastern Canada, who seek better irrigation strategies to optimize productivity. [ABSTRACT FROM AUTHOR]