Using AquaCrop model to derive deficit irrigation schedules for improved irrigation water management for tomato production in Zimbabwe

Abstract

Increasing scarcity and unreliability of rainfall, and the absence of irrigation schedules are challenges to decision-making, particularly for viable tomato (Lycopersicon esculentum Mill) production in Zimbabwe. The objective of this study was to determine water requirements of tomato as a basis for developing generic calendar guidelines for a more efficient irrigation management in Harare, Zimbabwe. We explored the options of improving the traditional, dry and supplementary wet season irrigation practices. By considering the archived climate data of thirty years (1991-2021) for Harare; and model-simulated consumptive water use from 2014 to 2017 at Thornpark Research Station, together with the crop and soil characteristics; and the irrigation method; an irrigation calendar was developed using the AquaCrop model 5.0. The improved irrigation schedule for dry season tomato cultivation at 60% ETc, resulted in water use of 471.6 mm, with a yield of 3.40 t ha-1; compared to water use of 820 mm and a yield of 1.118 t ha-1; for the wet season. Through this model, we have been able to estimate the time interval between the previous irrigation and the next irrigation for any date in the growing season. Therefore, year-round irrigated tomato production may be feasible with an added yield advantage of 2.28 t ha-1 obtainable using water and rainy periods.