干旱已成为世界农业和社会发展的制约因素。干旱和半干旱总面积约占陆地面积的34.9%,占耕地面积的43%,我国人口受干旱影响面积不断增加,20世纪50年代年平均受旱面积1133万hm2,80年代增加到2233万hm2,90年代达到2667万hm2,每年约有667万hm2耕地无 Drought has become a constraint on world agricultural and social development. The total area of ​​arid and semi-arid areas accounts for 34.9% of the land area, accounting for 43% of the arable land area. The population of our country is affected by the drought continually increasing. In the 1950s, the average drought-affected area was 11.33 million hm2. In the 1980s, it increased to 22.33 million hm2 Reaching 26.67 million hm2 in the 1990s and about 6.67 million hm2 of arable land each year