50年代,分布在我国南方14个省区,占全国土地面积21%的红壤尚未改良,大部分红壤不肥沃,农作物产量很低。当时长期从事我国土壤学研究的李庆逵教授,通过对红壤性质长期的研究,首次利用磷矿粉作为磷肥直接施到豆科绿肥上,获得良好效果,为农业生产上广泛采用“以磷增氮”的增产措施奠定了理论基础。他还进一步提出了对种植在强酸性土壤上多年生的经济林木橡胶树直接施用磷矿粉的方法,并布置长期的田间试验。结果表明,前4年 In the 1950s, the red soils distributed in 14 provinces and autonomous regions in the south of our country, accounting for 21% of China’s total land area, remained unimproved. Most red soils were not fertile and crop yields were low. At that time, Professor Li Qingxun, who had been engaged in soil science research for a long time in our country, got long-term research on the nature of red soil by using phosphate rock as the phosphate fertilizer for the first time and applied it directly to the leguminous green manure, obtaining good results and widely used for agricultural production. "Measures to increase production has laid a theoretical foundation. He further proposed a direct method of applying phosphate rock directly to perennial economic tree rubber trees planted in strongly acidic soils and arranged long-term field trials. The results show that the first 4 years