The Effect of Different Planting Date on Growth of Zea : II. On growth and grain yield under normal spacing.

Abstract

Early and late maturing varieties of corn plants were planted during the period from April 30 to July 6. The following conclusions were drawn out from this experiment. The grain yield of early maturing variety planted somewhat late is comparatively more than that planted at the other times of the season. On the other hand, grain yield of late maturing variety planted earlier is more than that of late planted ones. In the case of early maturing variety, dry matter weight per plant is less in the earlier planted one than those in somewhat late planted ones throughout the growth period. In the case of late maturing variety, during the early stage of growth period, accumulation of dry matter in early planted one is more than those in the later planted ones. During the time from early stage of growth period to silking, increase in dry matter weight of early planted one shows the tendency almost similar to that in the later planted ones. After silking, increase in dry matter weight of early planted one is accelerated more than that in the later planted ones. Increase in nitrogen and carbohydrate content seemes to be similar to that in dry matter weight throughout the growth period. Early maturing variety is insensitive to day length. Therefor, once the plant has accomplished its basic vegetative growth, tassel primordium differentiates even under long day regime. Assimilated carbohydrates are accumulated in grains under ideal condition throughout the ripening period in early as well as in middle planted ones, however, vegetative growth of the former is less strong than that of the latter, because the former plant has grown under lower temperature than the others during the course of vegetative growth. In consequence, amount of carbohydrate accumulated in grains is less in early planting. Plant growth and yield of early maturing variety planted late are less than those planted at the other time of season due to the same reason as the case of late maturing varieties planted late. On the other hand, late maturing variety is sensitive to day length. Tassel primordium does not differentiate untill day length become shorter, so amount of vegetative growth is more than that of early maturing variety. In late planting, however shorter day length restricts vegetative growth and lower temperature during ripening period degresses photosynthesis and accumulation of cabohydrate in grains, and these bring decrease in yield finally. Grain yield is better when seeds are planted earlier.