1965 Volume 33 Issue 4 Pages 403-408
The relations among planting time, plant population and irrigation in corn culture were investigated in order to appraise the practicability of irrigation in an early and a late season culture, in 1962. The results may be summarized as follows: (1) Weight of stover per are was decreased strikingly in late planting and increased with dense population and by irrigation. The effect of irrigation which appeared on the length of internode was larger in high population from early growing period. (2) The interval between tasseling and silking time and the percentage of barren plants were decreased by irrigation and were increased by late planting, and increased strikingly with increasing plant population in late planting. The irrigation lessened remarkably their increase by late planting and high population. (3) The number of kernels per m2 was increased by irrigation and was decreased by late planting. In early planting, the number of kernels per m2 increased as increasing plant population in both irrigated and non-irrigated plots. But in late planting, the number of kernels per m2 decreased with increasing population in the case of non-irrigation and increased with population rise in the case of irrigation. The irrigation lessened the decrease by late planting. The reason of different effects of dense population between irrigation and non-irrigation was considered as follows. Irrigation decreases the percent of barren plants and sustains the increasing of number of ears per are by high population and in addition lessens strikingly the decrease of number of kernels per ear by high population throuth the increase of length of ear and the decrease of variation of ear size. (4) Weight of 1, 000 kernels was increased by irrigation and was decreased by late planting and decreased with increasing plant population. The quality of grain was deteriorated by late planting, and was scarcely practical value except the case of low population level in irrigated plots. (5) The yields of grain showed similar tendency to kernel numbers per m2. The yields of grain were increased remarkably by irrigation and were decreased notably by late planting. In early planting, the yields of grain increased with population rise in both irrigated and non-irrigated plots, however, in late planting, decreased with increasing plant population in the case of non-irrigation, but increased with population rise to the population of 833 plants per are in the case of irrigation. On the yields of grain, the interactions of irrigation × plating time (0.1 % level) and irrigation × plant population in late planting (1 % level) were significant. (6) By the above results, it was made clear that 1) high grain yields of corn in early season culture are obtained by irrigation and higher plant population, and 2) late season culture of corn (planting early in July) is unvaluable in the case of non-irrigation but considerable high yields and relative good quality of grain are obtained in the cese of irrigation at low population level.
