Economic analysis of deficit irrigation in sugarcane farming: Nchalo Estate, Chikwawa District, Malawi

Sustenance of the growing world population calls for increased agricultural production. However, this will have to be done while forecasts of water withdrawals on a global scale predict sharp increases in future demand to meet human needs. The inadequacy of irrigation water supplies has led to the need to consider deficit irrigation (DI) as a water saving strategy. DI is a deliberate under-application of water to growing crops. In this study we carried out an economic analysis of DI in sugarcane farming with an aim of developing an understanding of the economic impact of various irrigation water management strategies. The study was undertaken at a 36.6-ha field in Nchalo sugar estate in Malawi. The AquaCrop model was used to simulate yield response of sugarcane to different water application levels. The model was calibrated and validated based on field data. The output from the simulations were used to generate a yield-water production function which was used in the economic analysis. The study showed that DI is a viable strategy that can be used at the estate when water is limited. The optimum water-limiting irrigation depth (Ww) was 120 mm and the optimum land-limiting depth (Wl) was 1,400 mm. When available water is less than Ww, it is recommended to apply an irrigation depth of Ww on a portion of the field and leave the rest of the field in rainfed conditions, which resulted in a small increase (up to $5,490) in the total net returns for the field. When the available water depth is greater than Ww but less than Wl, it is recommended to apply the available water depth across the whole field; this resulted in a large increase (up to $ 208,000.) in total net returns for the field compared to applying Wl on a reduced field area.