Optimizing Maize Yield, Nitrogen Efficacy and Grain Protein Content under Different N Forms and Rates

This study aims to evaluate the efficacy of nitrogen (N) forms: ammonium, nitrate, and urea on maize performance, N uptake and use efficiency, and the grain protein content. The experiment was laid out as a split-plot with the whole plot factor being the three fertilizer treatments and the subplot being four N levels (0, 25, 50, and 100 kg N ha −1 ) with three replicates. Plant tissues were analyzed for total N uptake. Grain and stover yields and grain protein were determined at maturity. The highest (62 cm) plant height (at the vegetative stage) was recorded in nitrate treatment. Grain yield was highest (2.9 t ha −1 ) in plots that received nitrate. Fertilization with nitrate enhanced grain protein more (11.6%) than when urea or ammonium was used. N uptake was highest (42 kg N ha −1 ) under ammonium treatment, intermediate (22 kg N ha −1 ) in those treated with nitrate, and lowest (21 kg N ha −1 ) in urea-receiving plots. Application of 25 kg N ha −1 resulted in the least N uptake efficiency with optimal values registered at 50 kg N ha −1 . Agronomic N use efficiency differed among the rates with values ranging from 44 to 183 t ha −1 per N kg ha −1 applied in the order of 25