ASSESSMENT OF THE NITROGEN REQUIREMENTS OF MAIZE (ZEA-MAYS L) IN SOUTHERN GUINEA SAVANNA AGROECOLOGY OF NIGERIA

During the growing seasons (May to October) of 1987 and 1988 respectively five and four different rates of N were tested on maize (Zea mays L.) at 12 different field sites across the Southern Guinea Savanna of Nigeria. Nitrogen was applied through granular urea (size +14 mesh), ordinary prilled urea (-35 mesh) and calcium ammonium nitrate. Marked differences existed among experimental sites in maize grain yield response to N with Yelwa and Ta-Hoss in Plateau State having the highest response at 60 and 90 kg N ha-1 respectively. During 1988, at five experimental sites the yield was maximized with 120 kg N ha-1, while at three other sites the yield maximization occurred at 90 kg N ha-1. During 1987, the corresponding number of sites was two and six with 120 and 90 kg N ha-1 rates, respectively. Plant height and cob number exhibited a linear relationship with yield. Differences in yield in response to application of different N sources were non-significant.