Assessment of grain yield and nitrogen use, efficiency in extra-early maize (Zea mays L.) varieties and their top cross hybrids under low N-fertilizer regimes in a typical Southern Guinea savanna ecology of Nigeria

Abstract

Assessment of maize (Zea mays L.) nitrogen (N) fertilizer requirements under low input farming system is necessary in order to develop maize production packages that will be compatible with resource poor farmers’ need. Nine extra-early maize varieties and their top cross hybrids derived by intercrossing unto a local variety (AFO) as the pollen parent were evaluated at the Teaching and Research (T&R) Farm of the University of Ilorin in a typical Southern Guinea Savanna (SGS) ecology of Nigeria, using five N-fertilizer levels (0, 20, 40, 60 & 80 kg Nha^-1 respectively). The objectives were to assess the performance of the genotypes for grain yield and nitrogen use efficiency (NUE) and also identify productive maize genotypes under low N-fertilizer regime consistent with farmers’ practice in the SGS zone. Grain yield and NUE differed significantly (P< 0.05 or 0.01) each season (S) with a difference of 0.27t/ha^-1 in grain yield between 1998 full growing season and 1999 late season but with a corresponding delay of 2 days in mid-silk in the varieties per se. Conversely, the expression of the two traits in the hybrids was similar in the two growing seasons of 1999. Grain yield increased with increase in N-dosage in both varieties and hybrids but was higher in the varieties per se relative to the hybrids while NUE showed no consistent trend at increasing N-levels except at 60 kg Nha^-1. However, the capacity to utilize N as measured by NUE was optimum at 40kg Nha^-1 in both varieties and hybrids. Differences in grain yield between 0 and 80 kg Nha^-1 were 1.07 and 1.34 t/ha^-1 respectively in both varieties and hybrids. Genotypic (G) effects differed (P< 0.01) for grain yield. NUE and other traits in the varieties per se while the hybrids also differed for these characters except NUE and ear height. The first order interaction of S x N was significant for both grain yield and NUE in both varieties and hybrids while G x S effect was  non-significant for both characters. Grain yield correlated  positively and significantly with growth morphological and flowering traits in the varieties per se, while NUE correlated positively and significantly only with seedling height, plant and ear heights as well as harvestable ears and grain yield. Var CSP-SR x TZE Y and its hybrid (CSP-SR x TZE y) x AFO combined high grain yield with superior for NUE. This indicates that the variety can be further tested under farmer’s conditions and can also be a source of inbred line extraction for developing N-stress tolerant varieties.

JARD Vol. 5 (2) 2006: pp. 112-128