Optimum Seeding and Nitrogen Fertilizer Rates for Maximizing Yield and Sustaining Rain-Fed Lowland Rice (<i>Oryza Sativa </i>L.) in Fogera Plain North-western Ethiopia

Abstract

Rice (<i>Oryza sativa</i> L.) is increasingly becoming an important food crop in Ethiopia. However, the average rice productivity in Ethiopia is estimated at 2.8 t ha<sup>-1</sup> which is much lower than the world average, 4.6 t ha<sup>-1</sup>. Its productivity is challenged due to a lack of appropriate and location-specific agronomic practices like the application of optimum doses of nitrogen fertilizer and the use of optimum seeding rates. Thus, a field experiment was conducted in Fogera district in South Gondar Zone, Northwestern Ethiopia during the 2021 main cropping season to determine the optimum dose of N level and seeding rate. The treatments comprised factorial combinations of four levels of N (134, 184, 234 and 284 kg ha<sup>-1</sup>) and four different seeding rates (60, 80, 100, and 120 kg ha<sup>-1</sup>). The experiment was laid out in a randomized complete block design and replicated thrice. All data on phenology, vegetative growth yield and yield-related parameters were collected and measured following scientific standards of each parameter. Those data were subjected to analysis of variance using the general linear model (GLM) procedures of SAS 9.0 version system. Economic analysis was also carried out by following CIMMYT partial budget analysis procedures. The analysis result showed the main effects of both, different levels of nitrogen and different rate of seeding, and their interactions showed highly significant effect on the number of both total and effective tillers, grain filling, panicle length, phonological parameters, totals spikelet’s, thousands seed weight, grain yield, biological yield and straw yield. Application of 184 kg N ha<sup>-1</sup> level with a seeding rate 100 kg ha<sup>-1</sup> gave the maximum grain yield (6,641 kg ha<sup>-1</sup>), the highest number of effective tillers per m<sup>2</sup> (792) and filled grains per panicle (95.34). Furthermore, the highest net return of ETB 118,850 with acceptable marginal rate of return (2,313%) was also obtained from the application of 184 kg N ha-<sup>1</sup> level and a seeding rate 100 kg ha<sup>-1</sup>. From the current research experiment, it is possible to conclude that increasing seeding rate beyond 100 kg ha<sup>-1 </sup>and N above 184 kg N ha<sup>-1</sup> is not economical yield of rice <i>“Selam’’ </i>variety in the study area. Rather, use of 184 kg N ha<sup>-1</sup> and seeding rate of 100 kg ha<sup>-1</sup> is promising for Lowland Rice (<i>Selam</i>) variety production under the rain fed condition in Fogera Plains and similar agro-ecologies of rain-fed growing area of Ethiopia for better economic and agronomic advantage.