Two field experiments were conducted at Bartha Experimental Station in EI·
Kaluobia Governorate during the two successive seasons 1999 and 2000 to study the
effect of some macro climatic and micro environmental factors and to evaluate some
parameters of three maize crosses, namely single cross 10 ( S. C. 10.), single cross
yellow 152 ( S. C. Y. 152.) and three way cross 321 (T. W. C. 321). Nitrogen was
added as urea (46% N) at three levels (60,90, 120 kg N! fed).The treatments were
arranged in randomized complete blocks design with four replications. Analysis of
variance. simple correlation coefficient, prediction equations of full model and
stepwise multiple regression, path coefficient analysis, phenotypic. genotypic and
environmental correlation coefficients were done. Data showed that yield of single cross 10 was higher than single cross yellow 152 and three ways cross 310. Nitrogen fertilization has significant affected for all characters under study. The results revealed that maize plants fertilized with 120 kg N! fed gave the highest values. Whereas single cross 10 (S.C. 10) +120 kg N! fed produced highest grain yield! plot in two seasons.
Highly significant and positive correlation coefficient were found between grain yield! plot with all characters. The full model regression including all factors ranged from 95% to 97% for all variables in two seasons 1999,2000 respectively while stepwise regression ranged from 85% to 93% for two seasons 1999.2000. It was found that the most important macro climatic factors and variables affecting grain yield of maize were day length in tassel initiation stage, growing degree day in silking initiation stage. relative humidity in six leaves exist on the plant. pollination and physiological maturity. In addition to variables ear length and number of kernels! ear. Nitrogen fertilization crosses and years as micro environmental factors had significant effects on grain yield of maize. Path coefficient analysis revealed that number of kernels! ear and number of
rows! ear were the most prominent direct effect on grain yieldl plant in the first season
with the highest relative importance value of 12.07% and 11.85%. respectively as
estimates of their relative contribution to the total variation of grain yield! plant. Both
number of kernels! ear. weight of 100 kernels have the most prominent direct effect on
grain yield! plant in the second season with the highest relative importance values of
40.96% and 4.53%. respectively as estimates of their relative contribution to the total
variation of grain yield! plant. In both seasons the total relative contribution of the
studied characters overall variation in grain yield was 88.04% and 71.64% respectively. Heritability values were estimate as a broad sense, it were relative high for the most of traits indicating that most variability among genotypes was due to causes. All variables had high heritability estimates and ranged from 53.60% to 91.91 % in both two seasons, except ear length and number of kernels! ear. In general, heritability estimates were high and comparable for most of the studied characters. Genotypic correlation coefficient between grain yieldl plot were positive and highly significant to ear diameter. number of kernels/ear and weight of 100 kernels in the first season whereas phenotypic and genotypic correlation coefficients were positive and highly significant to the number of kernels! ear and grain yieldl plant in the second season. All characters had positive and highly significant correlation coefficients with grain yieldl plant while number of rows! ear was negative and highly significant in the first season. In the second season it was found to be positive and highly significant to number of kemelsl ear while ear length was negative and highly significant.