法国位于北纬42——51度之间,面临大西洋,东南为地中海,冬季受海洋季风的影响,大部分地区冬季气候温和,夏季温暖,雨量充沛,季节分配均匀,生长季节较长。但在主要农业区巴黎盆地一带,5—8月份平均气温15.9——16.7℃,晚春和初夏易发生低温,每10年中还发生一两次秋季低温冷害。 1948年法国从美国引进玉米双交种W240、W255、W355和Iowd4417,这些杂交种比当地品种增产20—25%,但都因生育期较长,需肥水较多,在北部地区种植不能成熟,在西南部玉米产区易遭受早春低温危害,故推广面积不大。因此,使他们认识到培育早熟耐寒的玉米杂交种,是法国发展玉米生产的关键。 France is located between latitudes 42 - 51 degrees north, facing the Atlantic Ocean, southeast of the Mediterranean Sea, the winter monsoon by the sea, most parts of the mild winter climate, summer warm, abundant rainfall, seasonally distributed, growing season longer. However, in the main agricultural area of ​​the Paris basin, the average temperature in May-August is 15.9-16.7 ℃, low temperature is likely to occur in late spring and early summer, and once or twice in 10 years. In 1948, France introduced the double crosses of W240, W255, W355 and Iowd4417 from the United States. These hybrids increased the yield by 20-25% compared with the native varieties. However, both of them had to grow more fertilizers due to the longer growth period and could not be planted in the northern area. Maize producing areas in the southwest are vulnerable to low temperatures in early spring, so the promotion is not large. Therefore, to make them realize that cultivating early-maturing and cold-tolerant corn hybrids is the key to France’s development of corn production.