DETERMINATION OF NITROGEN AND PHOSPHORUS FERTILIZER RATES FOR RAIN-FED LOW LAND RICE ( oryza sativa L.) IN FOGERA PLAIN, SOUTH GONDAR, ETHIOPIA

Abstract

Rice is one of the cereal crops produced in Ethiopia. However, its productivity is very low (3.3 t ha -1 ) as compared to its yields potential in the world. The reasons for its low productivity is attributed to poor agronomic practices like inadequate nitrogen and phosphorus fertilizer rates, mono cropping system, weed, diseases, insect pests and other factors. Therefore, field experiment was carried out during the 2017 main cropping season from July to November in Fogera plain with the objectives of determining the optimum nitrogen and phosphorus fertilizer rates for rain fed low land rice production. A factorial combination of five levels of nitrogen (0, 92, 184, 276 and 368 kg nitrogen ha -1 ) and four phosphorus rates (0, 23, 46 and 69 kg P 2 O 5 ha -1 ) were tested in randomized complete block design (RCBD) with three replications. The results of the experiment showed that almost all the agronomic parameters like days to 50% heading and physiological maturity, plant height, effective tiller, panicle length, number of grain per spike, biomass yield, grain yield and harvest index were significantly (p<0.01) affected by the main effects of nitrogen and phosphorus fertilizer rates except thousand seed weight. The interaction effect of nitrogen and phosphorus fertilizer also indicated significant variations (p<0.01) on number of total and effective tillers, panicle length, harvest index and grain yield. The correlation analysis of yield and other traits indicated that grain yield positively correlated (P<0.01) with panicle length (r=0.91**), number of total tiller (r=0.91**), number of effective tiller (r=0.96**) and harvest index (r=0.97**). The graph of regression equation indicates that there is linear relationship between nitrogen and phosphorus fertilizer rates with grain yield. The e conomic analysis indicated that a combination of 368 kg N ha -1 and 69 kg P 2 O 5 ha -1 was the best profitable rate for rice production in Fogera plain and other similar agro ecologies. However, since the present observation is a one location and a single year experiment, further study has to be done under different seasons and locations to arrive at a dependable recommendation.