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Manure biochar influence upon soil properties, phosphorus distribution and phosphatase activities: A microcosm incubation study

Jin, Yi, Liang, Xinqiang, He, Miaomiao, Liu, Yu, Tian, Guangming, Shi, Jiyan
Chemosphere 2016 v.142 pp. 128-135
acid phosphatase, air drying, biochar, cation exchange capacity, clay loam soils, enzyme activity, esters, inorganic phosphorus, nuclear magnetic resonance spectroscopy, orthophosphates, phosphorus, pig manure, pyrolysis, silt loam soils, soil pH, stable isotopes
Using manure-derived-biochar as an alternative phosphorus (P) source has bright future prospects to improve soil P status. A 98-day microcosm incubation experiment was set up for two soils which were amended with manure biochar at proportions of 0, 0.5% and 1.5%. Swine manure samples were air-dried and manure biochar was prepared by pyrolysis at 400°C for 4h. As determined by P-31 nuclear magnetic resonance (³¹P NMR) spectroscopy, manure biochar mainly increased the contents and fractions of orthophosphate and pyrophosphate in two soils, while decreased those of monoesters (P<0.05). At the end of incubation, 1.5% of manure biochar raised soil pH by 0.5 and 0.6 units, cation exchange capacity by 16.9% and 32.2%, and soil total P by 82.1% and 81.1% for silt loam and clay loam soils, respectively, as compared with those soils without biochar. Simultaneously, 1.5% of manure biochar decreased acid phosphomonoesterase activities by 18.6% and 34.0% for clay loam and silt loam, respectively; while it increased alkaline phosphomonoesterase activities by 28.5% and 95.1% for clay loam and silt loam, respectively. The enhancement of soil P availability after manure biochar addition was firstly due to the orthophosphate and pyrophosphate as the major P species in manure biochar which directly increased contents of soil inorganic P, and also attributed to the decomposition of some organic P like monoesters by enhanced alkaline phosphomonoesterase activities from manure biochar addition.