1995年通过对四平市耕层土壤速效磷化验结果的汇总分析，并与1982年的化验结果进行比较，发现13年来耕层土壤速效磷有较大幅度提高，有三分之一以上耕地成为富磷土壤。 Through the summary analysis of the results of soil available phosphorus test in topsoil of Siping City in 1995 and comparison with the test results in 1982, it was found that available phosphorus increased significantly in topsoil in the past 13 years and more than a third of the cultivated land became rich Phosphorus soil.