玉米生育期热量指标及其不同品种的栽培北界

利用玉米分期播种资料，分析不同发育期发育速度与温度的关系得出：在作物营养生长期，用有效积温作为热量指标比较稳定；播种到出苗期，不同品种的生物学下限温度基本在８℃左右；出苗到抽雄所需的有效积温可用品种的叶片数来计算，有效积温与叶片数关系可以写成ｙ＝３０．２ｘ＋３１．８；进入繁殖生长期，用＞１０℃积温作为抽雄到成熟的热量指标，并用抽雄期进行订正。用播种到成熟各发育阶段的热量指标来确定能否成熟和因成熟度所造成的减产程度。把品种在８０％年份能够成熟的地区作为品种栽培的北界。

STUDY ON HEAT INDEX AT GROWING STAGES OF CORN AND NORTH PLANTING BORDER OF DIFFERENT BREEDS

Based on corn seeding data from different seeding periods, this paper analyzes the relatiionship of temperature and growing speed of corn at different growing stages.A conclusion is reached that it is relatively stable to use effectively accumulated temperature as heat index at nourishing growing stage.From seeding to emerging,lower limit of temperature is 8 which is hardly varies among the breeds. From emerging to heading accumulated temperature needed is calculated according to the number of leaves. And the relation of effectively accumulated temperature and the number of leaves is expressed as follows: y=30.2x 31.8. After entering reproductive period accumulated temperature of greater than 10 is considered as heat index from heading to ripening.And this heat index is corrected during heading. According to heat index of different developing stages from seeding to ripening, whether it will ripen can be determine, so can the extent of output reduction resulting from extent of ripening.And the north planting border of a breed is defined according to whether it ripens in 80 percent of the years.