| Phosphorus application in excess of crop needs has increased the concentration of P in surface soil and runoff and led to water eutrophication. Soil as a central media for the behavior of phosphorus, plays an important role in the distribution and translocation of phosphorus in the environment. Research in the translocation and transformation of phosphorus in soil-water system is of importance to environmental P management and controlling the eutrophication. A series of experiments and investigations in this paper were conducted to study the changes of P pool by a long-term applying fertilizer P, the translocation and transformation of phosphorus between interface of soil and water in relation to their environmental effects, using the upland fields from yellow soil area of Guizhou Province. The main research results were summarized as follows: The status of phosphorus under different land use patterns and its environmental effects analysis in yellow soils of hilly area was studied.1. The investigations turned out that with the successive planting of crops the mainly available nutrients accumulated yearly under normal fertilization in the upland fields form yellow soil area, especially the content of P increased obviously. The contents of Al-P, Fe-P and Ca-P in soil cultivated layer increased greatly. So the inorganic-P accounting for percents of total P increased obviously, but the organic-P accounting for percents of total P in the soil is obviously reduced under applying P fertilizer. The results showed that the contents of Olsen-P and total P in surface yellow soil layer of hilly area have significant difference under various land use patterns, the concentrations of labile P (CaCl2-extractable P) or algae-available P (NaOH-extractable P) also obviously difference in the soils, of which continuous tobacco land has higher level of P in the soils. The relationships between the contents of labile P and algae-available P in the soils and the content of Olsen-P or total P in the soil reachedsignificantly or extremely significant level, respectively. Therefore, Olsen-P, labile P and algae-available P in the soils accumulated gradually with long-term applying fertilizer P, which were favorable to the growth of crops, but enlarged the risk of P loss from soil to water bodies.2. The results showed that the contents of CaCh-extractable soil P, and soil test phosphorus(Olsen,Bray, Mehlich-3) and algae-available P contents (NaOH-extractable soil P) in the soils correlated significantly with the contents of Ortho-P, particulate P and bioavailable P in runoff, respectively, which were feasible to be used as primary indices to evaluate of agriculture P impacting on surface water quality. The results also showed that the relationships between the phosphorus sorption of soil index (PSI), and the degree of soil saturation with phosphorus (DPSS) and the contents of Ortho-P, particulate P and bioavailable P in runoff reached significant level, respectively. DPSS was the best index for evaluating of agriculture P impacting on surface water quality.CaCb-extractable P, Olsen-P, algae-available P, and PSI, DPSS were used as indices to estimate agriculture P impacting on surface water quality. As a result, three environmental risk groups were constructed as follows in the upland fields from yellow soil area.a Low Olsen-P (Olsen-P<10.0 mg.kg"1), DPSS<5.0% and low environmental riskto surface water quality,b. Medium Olsen-P (Olsen-P 20.0~40.0mg.kg'1), DPSS 5.0%~15% and medium environmental risk to surface water quality;c. High Olsen-P (Olsen-P>40.0 mg.kg'1), DPSS>15% and high environmental risk to surface water quality.3. By a pot experiment, the results showed that the contents of P, S and Ca increased with fertilizing ISO-POOkgPjOs/hm2 in the soil, especially the content of P increased obviously and that urease, dehydrogenase, phosphatase activities decreased with increasing the amount of fertilizer P, especially phosphatase activities reduced significantly, but polyphenol oxidase activity increased.
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