Effect of Nitrogen Fertilizer On Growth and Yield of Maize Varieties With Different Maturities in a Dry Agro-Ecology of Northern Ghana.

Declining maize yields due to a myriad of factors such as inherently poor soils, continuous cropping of cereal after cereal, high cost and unavailability of chemical fertilizers have all contributed to the above phenomenon.  To address this negative trend a field trial was conducted at the Manga Agricultural Research Station in the Upper East Region of Ghana, which represents a Sudan Savanna agro-ecology in the country. The trial was established as a randomized complete block design with 4 replications. The plot dimensions are 4.5 m x 5 m, and maize was sown on ridges made by bullocks. All cultural practices are as recommended for maize production in Ghana. For the extra-early maize, the, however, there were significant differences among the rates of N applied, with application of N at the rate of 120 kg ha^-1 recording the highest grain yield. For the early maturity group there were significant (P<0.05) variety by N rate interaction with TZE-W DT STR C4 recording the highest grain yield at 160 kg N ha^-1 and followed by TZE Comp DT C2 F2 at 120 kg N and 80 kg N ha^-1. For the medium maturity group there were significant variety by N rate interaction, however Obatanpa recorded significantly higher grain yield that the rest of the varieties. 120 kg N ha-1, also recorded the highest grain yield, which was significantly higher than those obtained at 0 and 40 kg N ha^-1. Nitrogen use efficiency decreased with increase in rate of N applied whilst rainfall use efficiency increased with increase in rate of N.  From economic analysis nitrogen rates of 40N and 80N both have marginal rates of return (MRR) > (MARR) (150%). This means that these treatments 40N and 80N could be recommended for uptake by farmers or for further research work.