Influence of Row Spacing and Seed Rate on Growth, Yield, and Productivity of Irrigated Rice in Somali Region

A field experiment was conducted in Gode, Kelafo, Jarati, and Dolo Ado experimental fields of the Somali region of eastern Ethiopia to evaluate the effects of seeding rate and inter-row spacing, as well as their interaction, on the performance of irrigated rice (Oryza sativa L.). This study is noteworthy as it addresses the lack of region-specific agronomic recommendations for irrigated rice in the Somali Region, where rice production is a recent practice under irrigation. Identifying the optimal inter-row spacing and seed rate is essential to enhance yield, improve resource use efficiency, and support food security in this under-researched agro-ecological zone. The study employed a factorial arrangement in a randomized complete block design (RCBD) with three replications, using the rice variety ‘Nerica-1’. Treatments included four inter-row spacings (10, 20, 25, and 30 cm) and four seeding rates (60, 80, 100, and 120 kg/ha). Results revealed that both seeding rate and row spacing significantly (P < 0.05 or P < 0.01) influenced most yield and agronomic parameters. Optimal effective tiller numbers were recorded at 60 kg/ha and 30 cm spacing, while the tallest plants (up to 82.32 cm) occurred at 120 kg ha⁻¹) and 30 cm spacing. The longest panicle length (22.73 cm) was observed at 10 cm spacing, although the highest number of filled grains per panicle (45.28) and maximum thousand seed weight (30.73 g) were achieved with wider spacing (30 cm) and moderate seed rates. The highest straw yield (6172 kg ha⁻¹) was obtained at the highest seeding rate (120 kg ha⁻¹), while the maximum grain yield (3624 kg ha⁻¹) was recorded at 100 kg ha⁻¹) with 30 cm spacing. These findings suggest that a seeding rate of 100 kg ha⁻¹) combined with 30 cm inter-row spacing optimizes rice productivity under irrigated conditions in the Somali Region. Future research could explore the interaction of inter-row spacing and seed rate with other agronomic factors such as fertilizer application and water management to further optimize irrigated rice production in the region.