The Evaluation Of The Potential Leaching Criterion Of 23 Soils From Different Regions Of China

As the continuous input of P fertilizer, phosphorus is gradually accumulated in the soils. The lost P from the soils through runoff and leaching becomes more and more the important source of P in water. In this study, 23 soils were collected from the croplands over the 13 China provinces or cities such as Linchuan Guangxi, Jianshui Yunnan, Liuzhi Guizhou, Zhangpu Fujian, Xiangshan Zhejian, Rugao Jiansu, Taian Shandong, Nanyan Henan, Yanan Shanxi, Haikou Hainan, Qianjian Hubei, Changsha Hunan and Haidian Beijing. Following adding 0, 30, 40, 60, 100, 160, 200, 240, 300, 400 mg P kg-1 soil (as KH2PO4 solution), and adjusting the soil moisture to 50% water-holding capacity (WHC), the soils were incubated at 25℃ for 4d .After the cycles of air-drying, rewetting and reincubating for three times, the soil P adsorption reached to equilibrium. The contents of Olsen-P, CaCl2-P and Fe-P were then respectively determined and the relationship between them was detected. The results showed that there was a significant linear relationship between Olsen-p and Fe-P. CaCl2-P increased sharply when either Olsen-P or Fe-P reached to a certain level, which was called as soil P leaching criterion. Considering this criterion values, the two soils from Xiangshan Zhejiang (soil No. 9 and No. 11) probably had P leaching, but low potential for the soils from Liuzhi Guizhou (soil No. 5) and Xiangshan Zhejiang (soil No. 10). Classical chemical and adsorption property of P in soil analysis suggest there's no apparent relationship between the leaching criterion and soil pH, exchangeable Ca & Mg, organic matter, CEC and adsorption property. While active Fe & Al positively affect the leaching criterion accordingly.