Effect of different nitrogen levels,plant population and soil nutrient status on yield and yield components of maize (Zea mays L.) in different ecological zones of Nigeria

Field studies on the effect of nitrogen levels, plant population and soil nutrient status on maize yield and yield components at eight different sites representing six different ecological maize growing zones of Nigeria conducted during 1976, 1977 and 1978 indicated that N significantly influenced yield at six of the eight sites, NIFOR, Umudike and Uyo (rain forest zone), Mokwa and Samaru (Savanna zone) and Riyom (derived savanna zone). Optimum N required for maize varies between 50 and 100 kgN in the different zones. There was no response to spacing except at Umudike, Uyo and Riyom, and no significant interaction between N and spacing at any location. Nitrogen application significantly influenced earweight at Ikenne, NIFOR, Umudike, Uyo and Mokwa. Nitrogen application had a significant effect on the number of cobs at NIFOR, Uyo and Mokwa, while spacing significantly influenced number of cobs at all locations except Uyo. Husk weight was significantly increased by nitrogen application at four locations, NIFOR, Uyo, Mokwa and Samaru, but spacing had no effect on this yield component in any of the other locations except Umudike. There was an N by spacing interaction on husk weight at Umudike and Mokwa. Nitrogen application significantly influenced lodging at tasseling at Uyo, Mokwa and Riyom, whilst there was a significant effect of spacing at Uyo and Samaru. At harvest, lodging was not influenced by N application but spacing significantly affected lodging at Ibadan and NIFOR. Both N application and spacing had no significant effect on shelling percentage at any location. The high correlation between relative yield and available Zn(r = 0.77), Cu (r = 0.63) and Fe (r = ? 0.66) of the soil at all the locations has shown that:

1. other nutrients besides N, P and K affected maize yield, therefore the inclusion of other nutrients besides N, P and K in the fertilizer recommendation for maize should be encouraged;
2. different levels of NPK fertilizer plus other nutrients are required in each ecological zone and this can be determined by soil testing.