RESPONSE OF WHEAT (Triticum aestivum L.) TO DIFFERENT RATES OF NITROGEN AND PHOSPHORUS AT FICHE-SELALE, CENTERAL HIGHLANDS OF ETHIOPIA

In Ethiopia, wheat is being cultivated on about 1.51 million hectares, with about 3.3 million tons of grain yield. However, productivity of this crop is low compared to its genetic potential. Field study was conducted in 2015 cropping season at Fiche. The objectives of the study were determining the optimum rates of N and P fertilizers, their concentration in plant parts and their use efficiency by wheat. The treatments were four level of N (0, 32, 64 and 96 kg/ha) and four level of P (0, 23, 46 and 69kg P2O5/ha). Randomized complete block design with three replications in factorial arrangement was used. The source of N and P were urea and TSP, respectively. Improved wheat variety, Digelu, was used as a test crop. The soil of the study area has moderate OM, high total N, low available P and moderately acidic pH. The interaction of N and P showed non-significant differences in crop phenology, spike length, thousand kernel weight, above ground biomass and grain yield, concentration of N in straw, concentration of P in straw, N uptake by straw, N uptake by grain, total N uptake, P uptake by straw and N use efficiency. However, there were highly significant differences for N and P in plant height, number of effective tillers/m2, number of grains/spike, residual total soil N content, residual total soil available P, concentration of N and P in wheat grain, P uptake by grain and total P uptake. The main effect of N was significant for days to 50% heading, biomass and grain yield, residual total N and available P in the soil, Concentration of N in the straw, N uptake (by straw, grain and total) and P uptake (by straw, grain and total), while days to maturity, number of effective tillers per square meter, spike length, number of grain per spike, thousand kernel weight, apparent recovery efficiency, physiological efficiency and agronomic efficiency of N showed non-significant differences for N. Similarly, P had significant effect on number of grain per spike, residual total N and available P in the soil and concentration of N in grain. The highest (3284 kg/ha) and lowest (2383 kg/ha) grain yields were obtained from application of 96 kg N/ha and 0 kg N/ha, respectively. The highest MRR % was attained under 96 kg N/ha (6998.80%) which was higher than other levels of N. Hence, 96 kg N/ha is profitable based on the result of study