Nitrogen species specific phosphorus mineralization in temperate floodplain soils

As an essential component of enzymes, higher N availability from agricultural runoff to forest soils may boost the activity of phosphatase, increasing the bioavailability of phosphate. The objective of this study was to evaluate P mineralization rates in temperate floodplain soils as a function of inorganic N species (i.e., ammonium and nitrate) and amendment rate (1.5–3.5 g N kg−1). Accordingly, the soil was amended with nitrate and ammonium, and P dynamics were monitored during a 40-day incubation. The addition of ammonium significantly boosted acid and alkaline phosphatase activity by 1.39 and 1.44 µmol p-nitrophenol P (pNP) g−1 h−1, respectively. The degree of increase was positively correlated with the amendment rate. Likewise, the P mineralization rate increased by 0.27 mg P kg−1 in the 3.5 g N kg−1 ammonium treatment. 31P nuclear magnetic resonance spectroscopic analysis further supported the reduction in organic orthophosphate diesters on day 30. Meanwhile, the addition of nitrate promoted P mineralization to a lesser degree but did not increase phosphatase activity. While floodplain soils have great potential to sequester anthropogenic P, high availability of inorganic N, especially ammonium, could promote P mineralization, potentially increasing P fertility and/or reducing P the sequestration capacity of floodplain soils.

Do methanotrophs drive phosphorus mineralization in soil ecosystem?

Experiments were carried out to elucidate linkage between methane consumption and mineralization of P from different phosphorous sources. The treatments were no CH4 no P amendment absolute control, with CH4 no P amendment control, with CH4 + inorganic P as Ca3(PO4)2 and with CH4 + organic P (sodium phytate). P sources were added at 25 µg P g-1 soil. Soils were incubated to undergo three repeated CH4 feeding cycle referred as feeding cycle I, feeding cycle II, and feeding cycle III. CH4 consumption rate k (µg CH4 consumed g-1 soil d-1) was 0.297 ± 0.028 in no P amendment control, 0.457±0.016 in Ca3(PO4)2, and 0.627 ± 0.013 in sodium phytate. Rate k was stimulated by 2 to 6 times over CH4 feeding cycles and followed the trend of sodium phytate > Ca3(PO4)2 > no P amendment control. CH4 consumption stimulated P solubilization from Ca3(PO4)2 by a factor of 2.86. Acid phosphatase (µg paranitrophenol released g-1 soil h-1) was higher in sodium phytate than no P amendment control. Abundance of 16S rRNA and pmoA genes increased with CH4 consumption rates. The study suggested that CH4 consumption drive mineralization of unavailable inorganic and organic P sources in the soil ecosystem.