20 0 0年 3～ 5月份共降水 15 .43mm ,这是建国以来最严重的春旱年 ,小麦减产 2 4.9% ,矮早麦穗粒数较前 4年平均数减少6 .7粒。而 1978年小麦同样是中后期干旱却比当时前后 7年的小麦平均单产增产 15 .3 % ,本文探讨了这两年一增一减的原因 From April to May in 2000, the total precipitation was 15.43mm, which was the worst drought year since the founding of PRC. The wheat yield decreased by 4.9% and that of the shortened early wheat grain decreased by 6.7% compared with the previous 4 years. In 1978, however, wheat was also in the middle and late droughts but increased by 15.3% more than the average wheat yield in the seven years before and after this period. This article explores the reasons for the increase or decrease in the past two years