Assessment of Nitrogen Management on Sunflower Yield and Its Economic Response in Smallholder Farms in a Semi-Arid Region

Although sunflower production in Tanzania is increasing, smallholder farmers still face a number of constraints that result in poor yields. Lack or inadequate nutrient supply is one of the main factors limiting crop productivity in Tanzania. However, mineral fertilizer is not always easily available and not economically affordable by smallholder farmers. Therefore, the use of animal manure could be a feasible and financially viable alternative, especially in the Dodoma region, where there is abundant livestock production. The aim is to analyze the effects of different animal manure rates on sunflower yield and the economic response of smallholder farms from Dodoma region. The dataset used in this study was obtained from a 2-year in loco survey. Sunflower yields under different animal manure rates were obtained using a process-based biophysical model, and results linked to an economic assessment. Results considering the 2015 and 2045 period showed a positive effect of animal manure application in sunflower yield (866.8 kg ha(-1)) under manure rate limiting 5000 kg ha(-1). The high rates of animal manure showed a decrease on yield providing evidence that water stress becomes the main limit factor for sunflower growth. Taking the economic assessment into account, an animal manure rate of 3000-5000 kg ha(-1) is the most appropriate fertilization management under the environmental and social conditions of Dodoma region, providing a profitable financial return to the farmers (283-416 USD ha(-1)). Therefore, sunflower is an attractive cash crop for Tanzanian farmers when the soil fertilization is properly managed.