Effect of Different Levels of Nitrogen Fertilizer on Yield and Agronomic Characteristics of Different Corn (Zea mays L.) Hybrids

This study was designed and implemented to investigate the yield and agronomic characteristics in three differently maturing corn (Zea mays L.) hybrids (SC704, SC500, and SC260) using four nitrogen (N) levels (0, 80, 160, and 240 kg N ha-1, from Urea, N= 45%). The experiments were conducted in Zabol (South-West of Iran) and Isfahan (Central Iran) in 2014 and 2015, respectively, using a split-plot arrangement in a randomized complete block design with three replications. Results revealed that the interaction effects of nitrogen × hybrid × location on the number of grain per ear, 1000-grain weight, nitrogen fertilizer use efficiency and grain yield were significant at 1% level. The interaction effects of nitrogen × hybrid on ear length, stem diameter, plant height, grain protein and dry mass yield were significant. Increasing the nitrogen application rate from 80 to 240 kg N ha-1 was found to increase ear length, stem diameter, plant height, 1000-grain weight, SPAD, grain protein and dry mass yield while it increased the nitrogen use efficiency. Increasing the nitrogen application rate from 80 to 160 kg N ha-1 was found to increase number of grains per ear and grain yield. The threshold level of nitrogen fertilizer requirement based on a 50% maize yield loss were determined to be 178 and 200 kg ha-1, respectively, in SC704 grown in Isfahan and Zabol, respectively. While the latter values were 164 and 192 kg ha-1 for SC500, and 150 and 186 kg ha-1 for SC260. It can be concluded that the SC500 had the highest grain yield at 160 kg N ha-1 in Zabol, and SC704 at 160 kg N ha-1 in Isfahan.