EFFECT OF PLANTING DATES AND N APPLICATION RATES ON MAIZE YIELD IN RELATION TO CHANGING PLANT DISTRIBUTION

This study was carried out during the two growing seasons i.e. 2003 and 2006 to study the effect of three planting dates (May, June and July), three nitrogen fertilizer rates (45 90 120 kg N/ feddan) and two plant distribution patterns (25 cm between hills with one plant/ hill 50 cm between hills with two plants/ hill), on yield of maize crop. Results obtained exerted significant effects on grain yield/ fad., stover yield/fad. and biological yield as planting date delayed from May to July, whilst vice versa trend was shown for harvest index. Grain yield decreased by 9.58% and 23.10% by delaying planting date from May to June and from June to July respectively in the first season and 31.19% and 40.82% respectively in the second season. No significant differences were appeared on grain yield, stover yield, biological yield or harvest index in the first season or stover yield and biological yield in the second season by changing plant distribution. Significant increases were appeared on grain yield/ fad. and harvest index with increasing N fertilizer application while biological yield/fad. tended to decrease. However highest grain yield was obtained at early planting date for plants grown 25 cm between hills and one plant per hill ; by early planting date andfertilized with high nitrogen doses and also by those planted at 25 cm and one plant per hill fertilized by highly nitrogen rate.