Ghana Journal of Agricultural Science

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Studies on performance of some open-pollinated maize cultivars in the Guinea savanna zone of Ghana. 1. Effects of plant density, nitrogen level and their interactions on yield

PYK Sallah, S Twumasi-Afriyie, PP Frimpong-Manso


Plant density and nitrogen (N) fertilizer responses of one local and three improved open-pollinated cultivars of maize (Zea mays L.) developed in different eras of maize breeding were studied on sandy-loam Alfisols in the Guinea savanna zone of Ghana in 1992 and 1993. A split-plot design was used in which plant densities (30 000, 50 000, 70 000 plants/ha) were the main-plots and 12 combinations of N fertilizer levels (0, 80, 160 kg N/ha) and cultivars (Local, Composite 4, Dobidi, Okomasa) were the sub-plots in four replicates. A cross location analysis for grain yield showed environment, plant density, nitrogen and cultivar effects were highly significant (P<0.01). The environment W ultivar, environment W nitrogen, density W nitrogen, and nitrogen W cultivar interactions were also significant (P<0.05). The density W cultivar interaction and all second- and third-order interactions involving the three factors were not significant. The mean yields were 3.08 and 4.51 t/ha for the local and the improved cultivars, respectively. For all cultivars, yields increased by 10 per cent after each 20 000 plants/ha increase in plant density. Similar N response patterns were observed for all the improved cultivars. Estimated biological optimum N rates were 154 kg N/ha for the local cultivar and 183 kg N/ha for the improved cultivars. Grain yields at the optimum N levels were 3.50 t/ha for the local and 5.53 t/ha for the improved cultivars. The greatest yield response to N was observed at 80 kg N/ha for all cultivars. The data showed that (1) improved cultivars out-yielded the local cultivar at low as well as at higher levels of soil fertility, (2) breeding did not result in varieties that required higher N rates to produce high yields, and (3) the data support the current N fertilizer recommendations for the Guinea savanna zone of Ghana.

Ghana Jnl agric. Sci. Vol.30(2) 1997:
AJOL African Journals Online