Studies on the Growth and Productivity of Maize for Whole-plant Silage in the North-Marginal Area, Nemuro District in Hokkaido : I. The effect of planting date on growth and yield

摘要

The ohject of this study is to investigate the effect of planting date on growth and yield of maize for whole-plant silage in the north-marginal area in Japan. Heigenwase, which is an early hybrid, was planted on four dates from mid-May to mid-June over a 4-year period (1976-'79), and some agronomic traits and yields were measured. The results obtained were as fllows: 1. Planting date markedly affected the speed of emergence and silking. As plantlng was delayed, emergence date and silking date were delayed in each year and the days from planting to emergence and from emergence to silking were reduced. Silking was affected by temperature, since efferctive heat-unit accumulation over 6°C from emergence to silking required 735±11°C constantly, regardless of planting dates. 2. As planting was delayed, top mean growth rates during the vegetative growth period were increased and those during the reproductive growth period were decreased in each year. During the reproductive growth period, stover mean growth rates were not affected by planting dates, but ear mean growth rates were obviously the greatest on the earliest planting date in each year. Top mean growth rates during the both vegetative and reproductive growth periods indicated highly positivc correlations (r=0.649, r=0.937) with effective heat-unit accumulation over 10°C. 3. The latest plantings always resulted in the highest stover DM yields, but no distinct stover DM yields advantage occurred with later planting. The earliest plantings led to the highest ear DM yields, total DM yields, TDN yields and percentage DM of whole-plant, and gave a distinct grain maturity advantage. 4. Ear DM yields and total DM yields indicated highly positive correlations (r=0.951, r=0.787) with effective heat-unit accumulation over 10°C during the ear-filling period. Percentage DM of whole-plant indicated a highly positive correlation (r=0.896) with accumulated temperature over 0°C during the ear-filling period. 5. Tpp dry-matter increment during the ear-filling period indicated highly positive correlations with ear DM yield, total DM yield, TDN yield, percentage DM of whole-plant and ear/total ratio. 6. From above results, it was concluded that under severe conditions like Nemuro district, early planting such as mid-May was essential for giving longer and warmer ear-filling period which could lead higher yield and quality for silage maize.