Effect of carbon additions on soil labile inorganic, organic and microbially held phosphate

Chauhan, B. S., author
Stewart, J. W. B., author
Paul, E. A., author
Agricultural Institute of Canada, publisher
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Investigations of the rate of P movement between soil inorganic, organic and biomass P compartments were carried out to clarify aspects of P cycling in soil systems. Organic carbon, as dried grass (33% C, 0.11% P) and cellulose (43% C), was added at a rate equivalent to 4000 kg organic material (OM)∙ha−1 every 30 days for 9 mo to the Ap horizon of a Chernozemic Black soil kept at field capacity moisture content and 24 ± 2 °C. In a third treatment, cellulose was added at the same rate with P (20 kg∙ha−1) at KH2PO4. Approximately 39% and 22% of the P added in grass and with cellulose, respectively, was found in organic P forms after 9 mo incubation. The remainder was found in NH4Cl-, NH4F- and NaOH-NaCl-extractable P forms which constituted part of the labile inorganic P pool and could be extracted by an anion exchange resin. Increases of biomass P during the first 4 or 5 days of each incubation period after residue addition were found to average 12 μg P∙g−1 in the first 3 mo incubation period. After this period, there was a smaller response in microbial P attributable to additions of grass or cellulose.
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soil system
field measurements
carbon sources
microbial activity
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