Amount of nitrogen and phosphorus fertilizer required to optimize growth and yield of rice

Soil nutrient management is an important factor in plant growth for increased crop production and productivity in Sub-Saharan Africa whose food demand is over the threshold. Rice production in Uganda is still very low with current yield less than 2.5 ton ha-1. The impressive production increase is mainly on to farmer area expansion. A fertilizer trial was established to determine a New Rice for Africa (NERICA) 4 variety response to the nitrogen and phosphorus application. At Tsukuba International Center, Japan, 2014 an experiment with objective to obtain the minimum fertilizer recommendation amount of nitrogen and phosphorus application dose was established during rice growing season May to September. The nitrogen (N) fertilizer rates were 0, 40 and 80 kg ha-1 while phosphorus (P) 0 and 70 kg ha-1 fertilizer quantities applied. Several data were obtained and indicated tiller number, panicle number m-2, plant dry matter were significantly (P<0.05) different from control. Yield and yield components were not significantly (P>0.05) different on application of different nitrogen doses. However, in P conditions, both nitrogen doses (40 and 80 kg ha-1) did not vary in ripened grains and number of spikelets/ m2. A significant amount of N was utilized when 40 kg N ha-1 was applied compared to 80 kg N ha-1 in similar P condition through growth stages. Applying N and P fertilizers at 80 and 70 kg ha-1 respectively, as well as applying N fertilizer 80 kg ha-1 alone increased growth parameters and yield compared to other rates of N and P fertilizers applied. Key words: Fertilizer rate, upland rice, New Rice for Africa (NERICA), N use efficiency