MICROBIAL PHOSPHORUS, AVAILABLE PHOSPHORUS, ORGANIC CARBON AND pH CHANGES IN CALCAREOUS, NEUTRAL AND ACIDIC SOILS INDUCED BY LOW MOLECULAR WEIGHT ORGANIC ACID ADDITION

摘要

Microbial phosphorus (P) as an active component of P pool plays an important role in regulating the availability of P to plants. Direct or indirect changes in soil pH, available P and organic Carbon (C) induced by low molecular weight organic acids (LMWOA) affect soil microorganisms, but have not been well considered in the contents of microbial P. This study aims to investigate the changes in microbial P, available P, pH and organic C induced by LMWOA in a calcareous, neutral and acidic soil. The relationship between microbial P and soil properties (soil pH, available P and organic C) was also explored. The soils were added with citric acid, malic acid, oxalic acid or their mixture (ratio, 1:1:1) at 0, 10, 20 or 40 mmol kg-1 soil. Soil microbial P, available P and organic C levels were increased and pH values were decreased to variable extents in the soils 15 days after the addition of LMWOA. No evident interactive effects among the organic acids were observed on the soil changes above mentioned. The change in microbial P induced by LMWOA was mainly ascribed to the direct effects from the changes in organic C, soil pH, available P, among which, the change in soil organic C had the most important positive impact.