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近十几年,作物(尤其是玉米)品种更新频繁。晚熟高产品种的使用,对粮食产量大幅度飞跃起到了决定性作用。但是,种子繁制使用周期长,在提前一年或两年确定明、后年主栽品种的时候,必然存在一定风险,而我们基层农业技术人员又很难提出精确的理论风险系数,以准确选择品种并分析其风险性。我们在整理双城市气象资料时,注意到与农业生产密切相关的几个气象指标(主要是年活动积温,无霜期,终、初霜日等)呈正态或接近正态分布。双城市1957～1991年气象资料统计表
In the past ten years, the varieties of crops (especially maize) have been frequently updated. The use of late-maturing and high-yielding varieties has played a decisive role in the substantial leap in grain output. However, the long-term seed multiplication and use of a year ahead of schedule or two years to determine the next major varieties of cultivars, there are bound to be some risks, and our grassroots agricultural technicians and difficult to put forward the exact theoretical risk coefficient to accurately Select breed and analyze its risk. When we compiled the meteorological data of Shuangcheng City, we noticed that several meteorological indicators closely related to agricultural production (mainly the annual accumulated temperature, the frost-free period, the end of the first frost date, etc.) were normal or nearly normal distribution. Meteorological data from 1957 to 1991 in Shuangcheng city