Effect of Blended NPS Fertilizer Rates and Row Spacing on Growth, Yield Components and Fresh Cob Yield of Maize (Zea mays L.) Under Irrigation in Nedjo District, western Ethiopia

Maize is one of the most important food crops grown in Oromia region of Ethiopia and is produced in different agro-ecologies in the region. However, its productivity is constrained by a number of problems. Among the several constraints in maize production, application of different blended NPS rates and planting space are the most important ones. A field experiment was conducted at Gamta Hamuma Kebele in Nedjo District, West Wollega Zone, western Ethiopia to assess the effects of application of different rates of blended NPS fertilizer and inter- row spacing on growth, yield components and green cob yield of maize and to estimate the cost benefit analysis of blended NPS fertilizer application on green cob yield of maize under irrigation in 2018/2019 off season. The experiment was arranged in a factorial combination of four levels of blended NPS fertilizer rate (0, 50, 100, and 150 kg NPS ha-1 ) and four inter- row spacing (55, 65, 75 and 85cm) in randomized complete block design with three replications. The result revealed highly significant main effect of blended NPS fertilizer rates and inter-row spacing on most of the measured phenological growth, yield components and yield of maize. Significantly, the highest days to 50% anthesis (82.92 days), days to 50% silking (89.33 days), leaf area (8047 cm2 ), leaf area index (4.69), days to hard dough stage (150.3), ear diameter (10.47), green cob yield (31.00 tons ha-1 ) and plant stand count at harvest (90.25 %) were recorded from the main effects of blended NPS fertilizer of 150kg NPS ha-1 . Similarly, significantly the highest days to 50% anthesis (80.25 days), days to 50% silking (86.08 days), leaf area (7198 cm2 ), ear diameter (10.21) and plant stand count (88.17%) were recorded from the 85 cm inter-row spacing and that of green cob yield (26.09 tons ha-1 ) was recorded from 75 cm inter-row spacing. From the interaction effects of NPS fertilizer and inter- row-spacing, the highest number of ears per plant (1.700), number of ears per hectare (66534) and the highest ear length (22.43 cm) were recorded from the application of 150 kg NPS ha-1 at 75 cm inter-row spacing whereas the highest plant height (285.3 cm) and the highest above ground biomass (143.33) were recorded from the application of 150 kg NPS ha-1 at 55 cm inter-row spacing. The highest economic benefit (314580 Birr ha-1 ) and higher acceptable MRR (138555%) was obtained from the combination of 150 kg NPS ha-1 and 75 cm inter-row spacing. Thus it can be concluded that application of 150 kg NPS ha-1 with inter-row spacing of 75cm was found to be superior both agronomically and economically for green cob yield of maize shone hybrid variety under irrigation in the study area.