Economic Benefits of Supplemental Irrigation in Uganda

Abstract

Rainfall variability and the recurrent droughts in the semi-arid regions of Sub-Saharan Africa have far reaching consequences. They have major effects on the socio-economic and environmental sustainability of rural communities. This study investigates the technical, economic, and financial feasibility of small-scale rain water harvesting, and supplemental irrigation (RWHSI) system to mitigate the negative impact of long droughts on crop production. The proposed system consists of limited farm grading to direct the harvested rain water to a lined earth-pond where several alternatives for pumping are proposed for supplemental irrigation schemes. The proposed scheme is mainly activated during the short period when the soil moisture is most critical for the crop yield. To reach an optimum size of the pond, the soil moisture during the critical growth period is simulated using FAO’s water productivity model (AquaCrop). The pond size is optimized by applying AquaCrop for several years with the actual rainfall pattern and the possible supplemental irrigation applications. For each year with its possible drought periods, crop yield for each pond size is predicted, then used for the economic feasibility of the pond sizes. The optimum pond size is the one maximizing its benefit over its cost. The feasibility of the proposed RWHSI is investigated on maize production for the Soroti area in Uganda. For the rainfall pattern, soil conditions, and maize growth characteristics of Soroti, the proposed RWHSI is proved by simulations to be technically, and economically feasible. For a typical farm holding with a catchment area of one hectare, an 800 cubic-meters lined earth-pond can give up to 50% increase in the maize yield. After considering the construction and running costs of the supplemental irrigation system, the pay-back period is 6 years. The required investment cost for this RWHSI is low, and likely to be within the financial capacity of many farmers, while their selection of the pumping system will depend on their manpower and financial ability.