Phosphorus in the microbial biomass of New Zealand soils under established pasture

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Abstract
A fumigation-extraction method was used to determine the phosphorus (P) content of the microbial biomass in a range of New Zealand high-producing pastoral soils. Despite high levels of extractable P in some soils, the increase as a result of fumigation was easily measured. Microbial P in the top 75 mm of the soils ranged from 10.5 to 57.4 kg P/ha (mean 31.8 kg P/ha) and could amount to several times that in the standing crop of the above-ground pasture. Microbial P was correlated with both bicarbonate-extractable organic and inorganic P. The correlations with extractable organic P were better than with extractable inorganic P, supporting the suggestion that NaHCO3 solutions extract a labile fraction of organic P from soils.