The researchers studied how different levels of nitrogen fertilizer affect water and nitrogen use in rainfed maize farming. They used a computer model to simulate how nitrate leaching, nitrogen uptake by crops, and soil nitrogen levels change with varying fertilizer amounts. The optimal fertilizer rate for rainfed maize was found to be 150 kg per hectare, as it resulted in the highest efficiency of nitrogen use. Increasing nitrogen beyond this rate did not improve crop yield and led to more nitrogen leaching into deeper soil layers. The model accurately predicted soil water and nitrogen dynamics, showing that excessive nitrogen can harm both crop productivity and the environment.