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The evaluation of phosphorus leaching risk of 23 Chinese soils I. Leaching criterion

2004; Elsevier BV; Linguagem: Inglês

1000-0933

Zhong Xiao,

Soil Carbon and Nitrogen Dynamics

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 Lingchuan Guangxi, Jianshui Yunnan, Liuzhi Guizhou, Zhangpu Fujian, Xiangshan Zhejiang, Rugao Jiangsu, Taian Shandong, Nanyang He'nan, Ya'nan Shaanxi, Haikou Hainan, Qianjiang Hubei, Changsha Hunan and Haidian Beijing. The soil samples were air-dried and sieved through 2mm mesh. Following adding 0,30,40,60,100,160,200,240,300,400 mg P/kg soil (as KH_2PO_4 solution), and adjusting the soil moisture to 50% water-holding capacity (WHC), the soils were incubated at 25℃ for 4d. The soils were air-dried, rewetted to 50% WHC and then incubated at 25℃ for 4d. The soil P adsorption reached to equilibrium after the cycles of air-drying and rewetting for three times. The contents of Olsen-P, CaCl_2-P and Fe-P were then respectively determined by pH8.5 0.5mol/L NaHCO_3, 0.01mol/L CaCl_2 and Fe strip filter paper. The results showed that there was a significant linear relationship between Olsen-p and Fe-P. CaCl_2-P increased sharply when either Olsen-P or Fe-P reached to a certain level, which was called as soil P leaching criterion. The values of the criterion were variable, depending on soil types. According to the relationship between Olsen-P and CaCl_2-P, the criterion values of Olsen-P ranged from 29.96~156.78 mg/kg soil, corresponding to 0.14~3.87 mg/kg of the CaCl_2-P. However, based on the relation of Fe-P to CaCl_2-P, the values of Fe-P and CaCl_2-P were 0.69~2.17 mg/kg soil and 0.30~7.38 mg/kg soil respectively. The criterion values from the two methods were similar in most of the tested soils, but greatly different in some soils. Considering the P leaching criterion values, the two soils from Xiangshan Zhejiang (soil No. 9) and Rugao Jiangsu(No. 11) probably had P leaching. The soils from Lingchuan Guangxi (soil No. 2), from Jianshui Yunnan (soil No. 3), from Nanyang Henan (Soil No. 15) and from Yanan Shanxi (soil No. 17 and No. 18) had high potential of P leaching, but low potential for the soils from Liuzhi Guizhou (soil No. 5 and No. 6), from Xiangshan Zhejiang (soil No. 10) and from Qianjiang Hubei (soil No. 20 and No. 21).