Effect of Nitrogen and Phosphorus Fertilizer Rates on Yield Components and Yield of Hybrid Maize (Zea mays L.) at Haramaya, Eastern Ethiopia

Nitrogen and phosphorus deficiency are the most important production constraint of maize next to moisture deficiency. Therefore, a field experiment was conducted at Haramaya University main campus research station (Rare), eastern Ethiopia, using a maize hybrid xv variety (BH 661) as a test crop in the 2015 cropping season. The objectives of the study were to investigate the effects of nitrogen and phosphorus fertilizer application on growth, yield components and yield of the maize crop, and to determine the economically feasible rates of N and P. The treatments consisted of four rates of nitrogen (0, 43.5, 87,130.5 kg N ha-1) and four rates of phosphorus (0, 23, 46, 69 kg P2O5 ha-1). The results revealed significant main effect of N and P rates on days to tasseling, silking, leaf area index, plant height, ear length, thousand kernels weight, biomass yield and grain yield. The highest leaf area index (4.4 and 4.3) as well as plant height (246.7 cm and 245.1 cm) was obtained at 130.5 kg N and 46 kg P2O5 ha-1, respectively. The interaction effect of N and P was significant on days to physiological maturity and number of ears per plant. The highest days to physiological maturity (185.7 days) was obtained at the rate of 130.5 kg N + 0 kg P2O5 ha-1 while highest number of ears per plant (1.84) was recorded at 130.5 kg N + 69 kg P2O5 ha-1. The highest grain yields of 10.77 and 10.90 t ha-1 as well as above ground biomass yields 23.91 and 23.95 t ha-1 were recorded in response to applying 130.5 kg N and 46 kg P2O5 ha-1, respectively. The main effect of N and P had significant effect on agronomic efficiency where the highest AE of 60.73 kg grain kg-1N and 56.03 kg grain kg-1P2O5 were obtained at 43.5 kg N ha-1and 46 kg P2O5 ha-1, respectively. The partial budget analysis revealed that the highest net benefit (52666 ETB ha-1) with acceptable marginal rate of return (286%) was obtained by applying N and P rates of 87 kg N + 46 kg P2O5 ha-1. From the results of this study, among N and P rates, N3P3 (87 kg N ha-1+ 46 kg P2O5 ha-1) can be tentatively recommended as economically optimum rates. However, further studies have to be conducted at various locations and years using more varieties of maize to reach at the conclusive recommendation.