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延安丘陵山区地处半干旱及干旱地带。年降雨量约500毫米左右,六、七、八、九四个月降雨量占全年降水量的70%左右,冬、春雨量极少,春旱频繁。据延安市26年的统计,发生春旱的概率为92%。春旱影响极大,夏粮得不到稳产高产,秋粮不能适时下种,有时严重缺苗翻种。因此,在干旱的丘陵山区推行旱农耕作力争高产稳产就成为客观的必然,搞好作物合理布局又是其中的重要一环。
Yan’an hilly mountain area is located in semi-arid and arid areas. The annual rainfall is about 500 millimeters. The rainfall in the sixth, seventh, eighth and ninety-four months accounts for about 70% of the annual precipitation. The rainfall in winter and spring is very little, and the spring drought is frequent. According to statistics of 26 years in Yan’an City, the probability of spring drought is 92%. Great impact of spring drought, summer grain can not be stable and high yield, fall grain can not be timely, sometimes serious lack of seedling. Therefore, it is an objective necessity to promote dry farming in the arid hilly and mountainous area and strive to achieve high and stable yield. To improve the rational distribution of crops is an important part of it.