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东北北部黑土区,土壤潜在肥力高,复季雨热同期,是我国重要的商品粮生产基地。但由于地处我国寒温带,农耕期(日平均温度高出0℃的持续期)仅200天左右,无霜期115～140天,≥10℃的积温2380～2900℃属一年一熟农作制,温度是影响该地区农作物产量主要限制因子之—。因此,在有限的作物生长季内,充分利用有效温度,提高耕地的复种指数,是农业增产增收,提高土地利用率的重要途径之一。
The black soil area in northeastern North China has high soil potential fertility and rainy season in the same season, which is an important commodity grain production base in China. However, due to the cold temperate zone in China, the farming period (the average daily temperature is higher than the duration of 0 ℃) is only about 200 days, the frost-free period is 115 to 140 days, and the accumulative temperature of ≥10 ℃ is 2380 ~ 2900 ℃ , Temperature is the main limiting factor affecting crop yields in the region. Therefore, within a limited crop growing season, making full use of effective temperature and raising the multiple cropping index of cultivated land is one of the important ways for increasing agricultural output and increasing land utilization rate.