Assessment of Irrigation Water Requirement for Major Vegetable Crops Using Penman-Monteith and Alternative Models in Northern Togo

Abstract

Climate change has seriously impacted water availability and agriculture production in arid and semi-arid climates. Estimation of actual crop evapotranspiration (ETa) is critical for agricultural water resource management and proper irrigation scheduling. This study aimed to (1) estimate the reference evapotranspiration (ETo) and four vegetables actual ETa during crop off season using Penman–Monteith method and alternative climatic data models and, (2) to determine the irrigation water requirement for these main vegetable crops in northern Togo. Four (4) ground based weather stations were considered across the northern region of Togo for 1987 - 2016 period. Non parametric Mann-Kendall test was used for the significance of the trend analysis of off season reference and actual evapotranspiration. The results showed a decreasing trend in off season ETo at Dapaong, Mango and Kara weather stations while Niamtougou showed an increasing trend in the long term ETo. From all stations, only Niamtougou had a significant increasing trend in ETa for all vegetable crops under this study. Among the study locations, Mango had the highest irrigation water requirement for all four vegetable crops, followed by Kara. The lowest irrigation requirement was obtained at Dapaong. These results will help in irrigation planning for tomato, cabbage, carrot and onion in the semi-arid climate of Togo and similar environment.