Abstract

Rice agronomy plays a great role in increasing and sustaining rice production and productivity. Due mainly to its relatively recent history of cultivation in Ethiopia, the scientific information available with regards to the response of rice to N and P sources of fertilizers for its production is very limited. An experiment was conducted in 2014 and 2015 in Tigray, Ethiopia, with the objectives of determining the economically optimum rates of N & P sources of fertilizer on yield of rice. Five levels of N (0, 23, 46, 69 and 138 kg N/ha) and four levels of P (0, 23, 46 and 69 kg P2O5/ha) Factorial experiment was laid out in a randomized complete block design with three replications. The interaction effects of N and P were significant (P ≤ 0.05) for grain yield, biomass yield, plant height and days to heading but not for days to maturity, harvest index and thousand seed weight. From the view point of the physical (agronomic) yield, the combined results of the experiment revealed that the combination of 138 kg N/ha and 46 kg P2O5/ha recorded maximum grain yield of 5723 kg/ha and the control (i.e. no N and no P) gave the lowest grain yield (1601 kg/ha). Unlike that of the agronomic yield, the economic analysis of the combined result of the experiment with two years and two locations revealed that the profitable mean net return of 22208.63 Birr/ha was obtained for the plot that received 69 kg N/ha and 23 kg P2O5/ha which is 11185.12 Birr more than the net returns obtained from the control (with no urea plus no DAP) which is Birr 11023.51 birr. Therefore, from the economically profitable fertilizer rate use point of view, rice farmers in Tselemti district and similar areas should use the most economically feasible fertilizer rate with highest value of marginal rate of return i.e. 69 kg N/ha with 23 kg P2O5/ha.

Keywords: Agronomic Yield; Economic Yield; Fertilizers; Marginal Rate of Return; Rice; Tigray