Performance of UREAstabil in the Nitisols and Vertisols of North-Western Ethiopia

Nitrogen is a critical yield-limiting plant nutrient for crop production in Ethiopia. The demand for synthetic fertilizer is significantly increasing. Urea is the main source of synthetic nitrogen fertilizer that mainly applied in the surface resulting in significant nitrogen loss. UREAstabil fertilizer is urea with N-(n-butyl) thiophosphoric triamide (nNBPT) that reduce the rate of urea hydrolysis by urease to reduce nitrogen loss and increase crop productivity. The research was conducted in Yilmana Densa district, Ethiopia for two years to evaluate the performance of UREAstabil compared to urea. The research evaluated the effect of UREAstabil fertilizer technology on bread wheat and tef at Nitisol and Vertisol. The finding of this research denies our prior hypothesis that UREAstabil could give better yields of tef and wheat with lower rates of nitrogen at single application rate compared to urea. Reducing the amounts of nitrogen by one third using UREAstabil resulted in an intolerable significant yield penalty for all the study sites and both years on wheat. Both the grain and straw yields were increased by splitting the UREAstabil, indicating that the enzyme that hydrolysis urea was merely inhibited. Considering a non-significant yield difference between the conventional urea and UREAstabil for all crops, soils, rates, and forms of applications UREAstabil is not promising. Further research with different rates of nNBPT as well as different nitrification inhibitors needs to be evaluated for their efficiency to improve crop yield and reduce nitrogen loss for different crops, different soils, and agro-ecologies.