EFFECT OF PLANTING DATE ON GROWING DEGREE DAYS, GROWTH AND PRODUCTIVITY OF SOME MAIZE HYBRIDS

Two field experiments were carried out at the Experimental Farm of Agricultural Research Center, Egypt, to investigate the effect of different sowing dates (May 15, June 1 and June 15) on the vegetative growth, flowering traits, growing degree days, yield and grain quality of some white maize hybrids (S.C 10, S.C 128, S.C 131, S.C 2031, T.W.C 321, T.W.C 324 and T.W.C 329) during 2017 and 2018 seasons. The results obtained could be summarized as follows: 1-     The results indicated that early planting surpassed the other planting dates in most growth characters (number of leaves/ plant, leaf area/ plant, stem, leaves and shoot dry weight/plant), photosynthetic pigment (total chlorophyll), physiological parameters (crop growth rate, relative growth rate and net assimilation rate), flowering characters (days to tasseling, silking and maturity), yield (plant height, ear height, ear length, ear diameter, number of rows / main ear, number of grains / row, grains weight/ ear, grain yield/fed, stover and biological yields/fed and harvest index) and grain quality (oil and protein %) in both seasons. 2- There are significant differences among the tested hybrids in most characters studied. S.C 2031 hybrid was generally superior to the other hybrids in all growth characters, chlorophyll content, yield (number of ears/plant, 100-grain weight, grain weight/ear and grain yield/fed) and protein percent in grains. However, S.C 131 and S.C 128 hybrids produced generally the highest values of days to maturity, ear diameter, stover and biological yields/fed and oil percent in grains. 3- The interactions between sowing dates and maize hybrids were found to be significant for most characters under study. It could be concluded that planting S.C 2031 hybrid which the best hybrid under early planting (May 15) condition, while S.C 131 hybrid showed the best performance under mid planting (June 1) condition compared to other hybrids. However, T.W.C 321 exhibited the maximum grain yield /fed under the late planting (June 15) in comparison with other hybrids under the environmental conditions of this experiment.