Nitrogen Use Efficiency and Grain Yield in a Diallelic Cross of Maize Populations

The high cost of inorganic fertilizer in West and Central Africa has necessitated an investigation into the nitrogen optimum fertilizer rate for profitable maize production. The performance of ten early open pollinated varieties (OPVs) and their F1 hybrids for grain yield and nitrogen use efficiency (NUE) was assessed, and productive cultivars under low N fertilizer regimes were also quantified. The trials (ten OPVs and their F1 hybrids) were set up in a split plot arrangement with three N fertilizer levels (0, 45 and 90 kg N ha-1) as main plot and the genotypes as sub-plot. Each plot was four-row, laid out in a randomized complete block design (RCBD) of four replications. Field experiments were conducted at the teaching Research (T and R) farm of the University of Ilorin, in the southern Guinea savanna of Nigeria. Planting was carried out during the growing season on 20th July, 2005 and 2nd July, 2006. Ten open pollinated maize cultivars were crossed in a half diallel to generate 45 F1 hybrids during 2004 and 2005 growing seasons. Observed agronomic characteristics were grain yield, establishment plant count, days to 50% tasselling and silking as well as plant and ear heights. All observed characteristics amongst all the genotypes during growing season in 2005 were better than those in 2006. Expressions of all characteristics in the selected hybrids including the grain yield were relatively higher than the OPVs. The total increase in grain yield was 1.72 t ha-1 and 1.95 t ha-1 for OPVs and hybrids respectively on application of 90 kg N ha-1 over no N-application. However, nitrogen use efficiency (NUE) was optimum at 45 kg N ha-1 in both groups. Grain yield and NUE correlated positively with growth characters measured except for days to 50% silking. Higher genetic gains were recorded for plant and ear heights. The hybrids Acr 90 Pool 16-Dt × Ak 95 Dmr-Esrw, Tze Comp4 C2 × Ak 95 Dmr-Esrw and Tze Comp 4 C2 × Tze Comp 3 C2 had higher grain yield with superiority for NUE (P< 0.05). It suggested that the hybrid combinations can further be tested under commercial growing conditions or can be introgressed with other released cultivars to develop low N-tolerant varieties in the in the Nigeria’s savanna ecologies.