Effect of level and time of nitrogen fertilizer application on growth, yield and yield components of maize (Zea mays L.) at Arba Minch, Southern Ethiopia

Maize is most important cereal crop used for human diet, livestock fed, and for many industrial applications in many parts of the world. However, the national average productivity is quite below the world average which might be attributed to nutrient deficiency among many problems. A field experiment was conducted during 2016/2017 croppping season to determine the effect of level and time of nitrogen fertilizer application on growth, yield, yield components and economics of maize cultivation. The experiment consisted of six levels of nitrogen and four times of application laid out in Randomized Complete Block Design with three replications. The analysis of variance showed that phenological and growth parameters as well as yield and yield components were significantly (P<0.05) affected due to N levels. Time of N application showed significant effect on all parameters except plant height, dry matter and ear height. The interaction between level and time of nitrogen application was significant for days to silking, number of kernels per ear and grain yield. The highest grain yield (9037 kg ha-1) was recorded when applying 69 kg ha-1nitrogen  in three splits, while the lower grain yield (4316 kg ha-1) was recorded from the control treatment. Grain yield showed high, significant and positive linear correlations with growth, phenological and yield components except days to maturity. The maximum economic benefit (51,843 Birr ha-1) and high acceptable (2018%) yield were obtained when applying nitrogen at 69 kg ha-1 in three splits and recommended for maize cultivation at Arba Minch. Key words: Economics, dose and time of N application, maize, nutrient, yield components.