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【Objective】 The low mobility of phosphorus in soil is a main factor limiting its bioavailability. In this paper. The efficacy of straw incorporation and biochar amendment in improving Olsen-P and changing P fraction is soil was studied. 【Method】 The study was based on incubation experiment. Soil taken from a rice field was used in experiments under two soil water contents to mimic paddy field and dried land, respectively. For each soil water treatment, there were four soil amendments: a high (BC2) and a low (BC1) biochar amendment, a high (SC2) and a low (SC1) straw incorporation. The control is without soil amendment (CK). The Hedley phosphorus speciation method was used to classify P fraction in each treatment, and the Olsen-P content and other soil physicochemical properties were measured using standard methods. 【Result】 Depending on its application rate, biochar amendment increased Olsen-P content in the dried soil and the paddy soil by 1.78 to 1.46 mg/kg and 12.04~22.42 mg/kg, respectively. Straw incorporation increased Olsen-P content in the dried soil and the paddy soil by 4.46~1.72 mg/kg and 6.37 to 4.27 mg/kg, respectively, also depending on its application amount. The phosphorus components varied with treatment but in all treatments, it was found that HCl-P>NaOH-P>NaHCO3-P>H2O-P. Biochar amendment increased soil pH, total nitrogen (TN), soluble organic carbon (DOC) and organic carbon (SOC) content, while straw incorporation increased soil total phosphorus (TP), DOC and SOC content. In soil amended with biochar, Olsen-P content was positively correlated with H2O-P, NaHCO3-P, SOC and NH4+-N, at significant level, while in soil amended with straw, Olsen-P content was positively correlated with NaOH-P, HCl-P, TN and NH4+-N, also at significant level. 【Conclusion】 Biochar amendment and straw incorporation promoted accumulation of Olsen-P in the soils, primarily affected by change in soil pH, TN, and SOC, as well as the changes in phosphorus components. These enhanced the bioavailability of phosphorus. |
