Abstract:
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.
