Assessment of the Relative Yielding Abilities and Stability of Maize (Zea mays L) Genotypes under Different Levels of Nitrogen Fertilization across Two Agro- Ecological Zones in Ghana

Abstract. Farmers" adoption of hybrid varieties would reduce the large discrepancy between current low yields and achievable yields reported by researchers in yield evaluation trials. This is because hybrids wield superior genetic potential over improved open pollinated varieties (OPVs) and local varieties due their heterozygosity which explains their exhibition of high heterosis in yield and general performance. The current low yield necessitated the need to undertake this study to assess the relative yielding potentials of 3 hybrid varieties, 5 OPVs, 1 local variety and 4 inbred lines under three levels of Nitrogen fertilization in forest and transitional ecological zones in the Ashanti region of Ghana. Analysis of variance (ANOVA) revealed significant interactions for genotype by location (G x L), genotype by nitrogen (G x N) and genotype by nitrogen and by location (G x N x L) for grain yield. Averaged across test environments (i.e. location by nitrogen levels), "Mamaba", a Quality Protein Maize (QPM) hybrid recorded the highest mean grain yield of 4.73 t ha -1 whilst the highest yielding OPV, Golden Jubilee, recorded 2.91 t ha -1 ;"Entry 5", the highest yielding inbred line however recorded grain yield of 0.72 t ha -1 . GGE biplot analysis for mean yield also showed that hybrids had better yielding abilities than OPVs under both low and high nitrogen fertilization and at different environments. In order to bridge the gap between the current low yields and achievable yields in Ghana, farmers would need hybrid seeds together with adequate levels of fertilizers