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TECHNICAL REPORTS

Waste Management

Organic Phosphorus Fractions in Organically Amended Paddy Soils in Continuously and Intermittently Flooded Conditions

^a Key Laboratory of Yangtze Aquatic Environment, Ministry of Education, The College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, P.R. China
^b Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, P.R. China

^* Corresponding author (cmyang{at}mail.tongji.edu.cn)

Received for publication May 16, 2005. Soil organic phosphorus (SOP) can greatly contribute to plant-available P and P nutrition. The study was conducted to determine the effects of organic amendments on organic P fractions and microbiological activities in paddy soils. Samples were collected at the Changshu Agro-ecological Experiment Station in Tahu Lake Basin, China, from an experiment that has been performed from 1999 to 2004, on a paddy soil (Gleysols). Treatments consisted of swine manure (SM), wheat straw (WS), swine manure plus wheat straw (SM + WS), and a control (chemical fertilization alone). Organic amendments markedly increased soil total organic phosphorus (TOP) and total organic carbon (TOC), especially in continuously flooded conditions. Based on the fractionation of SOP, organic amendments significantly increased soil labile organic phosphorus (LOP), moderately labile organic phosphorus (MLOP), and moderately stable organic phosphorus (MSOP) compared with the control. For SM and SM + WS treatments, LOP in continuously flooded soils decreased by 30.1 and 36.4%, respectively, compared to intermittently flooded soils. In organically amended soils, continuous flooding showed significantly lower microbial biomass phosphorus (MBP) and alkaline phosphatase activities (APA) than intermittent flooding. In intermittently flooded conditions, incorporating organic amendments into soil resulted in greater P uptake and biomass yield of rice than the control. In the intermittently flooded soils, APA (P < 0.05) and MBP (P < 0.01) were significantly and positively related to TOP, LOP, MLOP, and MSOP, whereas in continuously flooded soils, there was a significant (P < 0.05) negative relationship between MBP, TOP, and MSOP. Based on soil organic P fractions and soil enzymatic and microbiological activities, continuous flooding applied to paddy soils should be avoided, especially when swine manure is incorporated into paddy soil.

Abbreviations: APA, alkaline phosphatase activity • HSOP, highly stable organic phosphorus • LOP, soil labile organic phosphorus • MBC, microbial biomass carbon • MBP, microbial biomass phosphorus • MLOP, moderately labile organic phosphorus • MSOP, moderately stable organic phosphorus • NPA, neutral phosphatase activity • SM, swine manure • SOP, soil organic phosphorus • TOC, total organic carbon • TOP, total organic phosphorus • WS, wheat straw