Response of Upland Rice to Nitrogen and Phosphorus Fertilization on Vertisols of Tigray, Ethiopia

Nitrogen and phosphorus are often cited as the most limiting nutrients in agricultural soils of Ethiopia. Their availability in the soil solution also determines the growth and productivity of the soils and crops. Thus, experiments were conducted to investigate the response of upland rice and determine the optimum rates of N and P fertilizers. Experiments were conducted at four sites of Tselemti district (Tsaeda-Kerni, Mizikir, Maitsebri and Sekota-Mariam), Northwestern Tigray, Ethiopia. A factorial combination of two factors, four levels of nitrogen (0, 23, 46, 69, kg N ha-1 designated as N0, N1, N2 and N3, respectively) and four levels of phosphorus (0, 10, 20, 30 kg P ha-1 designated as P0, P1, P2 and P3, respectively) were conducted on complete randomized block design (CRBD). Data on yield and yield components of upland rice were collected and subjected to ANOVA through SAS software V9. Results showed that plant height, number of spikelet and total seed per panicle of upland rice were significantly increased when nitrogen and phosphorus fertilizers interacted at higher doses There were significant differences of main effects on panicle length, grain yield and straw yields of rice. Significantly higher grain and straw yields were obtained in plots receiving 69 kg N ha-1 compared to preceding treatments, and application of either 20 or 30 kg P fertilizer ha-1 can also boost the yields of upland rice in the district. However, the optimum grain yield of rice to the application of N and P fertilizers was not found in the response curve which indicates an extra application rates should be tried. Further, the highest agronomic efficiencies were also observed in the lower rates of both main effects.