Nitrogen and seeding rate optimization for bread wheat (Triticum aestivum L.) under irrigation in Metema and Belesa, Northwestern Ethiopia

Bread wheat is a major food and industrial crop in Ethiopia, and its productivity under irrigation influenced by appropriate nitrogen and seed rate. However, information on the optimum rate of nitrogen and seed rates for bread wheat under irrigation is limited in the study areas. Therefore, this study was conducted to identify the optimum nitrogen and seed rates for bread wheat under irrigation conditions at Metema (Metema research station) during 2021 and 2022 and at Belesa (on-farm) in 2022. The experiment consisted of four N rates (0, 92,184, and 276 kg ha− 1) and four seed rates (75, 150, 225, and 300 kg ha− 1) arranged in a factorial Randomized Complete Block Design (RCBD) with 3 replications. Growth parameters, yield components, and yield were measured and analyzed using SAS. The results showed that growth and yield components parameters were increased with increasing nitrogen rate up to 276 kg ha− 1 in both locations. The interaction between seed and nitrogen rates was significant for spike length, grain yield, straw yield, and biomass yield, whereas non-significant for other parameters at Metema. The combined interaction results of 276 kg N ha–1 with 225 kg ha–1 seed rate gave the highest grain yield (5178 kg ha− 1), while the lowest grain yield (1250 kg ha− 1) was obtained at the control plot and 150 kg ha–1 seed rates in Metema. At the Belesa district, the highest grain yield (3066 kg ha–1) of bread wheat was obtained at main effect of 276 kg N·ha− 1 and 300 kg ha− 1 seed rate. However, the lowest grain yield (678 kg ha–1) and (1395 kg ha–1) of bread, wheat was recorded from the control and the main effect of 75 kg ha− 1 seed rate. On the other hand, the partial budget analysis also showed that the highest net benefit was achieved at 184 N kg ha− 1 with 225 kg ha− 1 seed rate followed by 184 N kg ha− 1 with 150 kg ha− 1 seed rate in Metema. The highest net benefit in Belesa also found at 184 N kg ha− 1 with 300 kg ha− 1 seed rate followed by 184 N kg ha− 1 with 225 kg ha− 1 seed rate. Therefore, a 184 kg ha–1 nitrogen rate with 225 kg ha–1 seed rate as the primary option and, 184 kg N ha− 1 with 150 kg ha− 1 seed rate as a secondary option recommended for cultivating wheat in the under irrigation at Metema and similar agroecologies. For Belesa and similar areas, 184 kg N ha− 1 with 300 kg ha− 1 seed rate as the primary option, and 184 kg N ha− 1 with 225 kg ha− 1 seed rate as a secondary option is recommended in bread wheat production under irrigation condition. Future research shold evaluated the economic profitability, nitrogen use efficiency, and environmental impact of nitrogen application across different soil types.