Optimize planting density and nitrogen fertilizer rate on green cob and grain yield of maize ( L.) under irrigation in North Shewa, Ethiopia.

Nowadays producing maize for green cob is a profitable business in addition to producing maize for grain yield. High plant density has been widely used to enhance grain yield in maize. A field experiment was conducted at four locations for two consecutive years (2021-2022) to determine the optimum plant density and nitrogen level and to assess the advantage of selling the green cob rather than the grain yield. The experiment was laid out in a Randomized Complete Block Design in a factorial arrangement with three replications. Three plant populations (44,444, 66,666, and 88,888 plants ha) with five nitrogen levels (0, 46, 92, 138, and 184 kg ha were combined by factorial combinations and tested in the experimental plots to select the optimum level for high grain and green cob yield. The maximum grain yield (8656 kg ha) was obtained under the highest plant population (88,888 plants ha), and from tested nitrogen rates 46, 92, and 138 kg nitrogen ha gave statically similar higher yield. Based on partial budget analysis, the application of 92 kg ha-1 nitrogen under 88,888 plant population was more economically feasible than other treatment combinations. This result showed 23.42 % yield advantages compared to the positive control. In addition, applying 138 kg N under 88,888 plant densities was the most profitable compared to other combinations to produce green cob. Thus, the blanket recommended plant population, 44,444 plants ha with application of 46 kg N ha is insufficient for maize green cob and grain yield production. Rather use of 88,888 plants ha with the application of 92 kg N ha for grain yield production and the use of 88,888 plants per ha with the application of 138 kg N ha is profitable for the production of maize green cob.