Phosphorus cycling in wheat-pasture rotations, 2. The role of the microbial biomass in phosphorus cycling.
1988
McLaughlin M.J. | Alston A.M. | Martin J.K.
The incorporation of P derived from fertilizer and plant residues into the soil microbial biomass was studied under field conditions by using isotopic labelling. The 33P-labelled medic residues (Medicago truncatula cv. Paraggio) and 32P-labelled fertilizer were added to a solonized brown soil (Calcixerolic xerochrept) before sowing of a wheat crop (Triticum aestivum cv. Warigal). Amounts of 31P, 32P and 33P in the microbial biomass were determined at 0, 7, 18, 32, 36, 61, 81 and 95 days after sowing. Amounts of 31P in the microbial biomass were closely related to gravimetric soil water content. Due to banding of the fertilizer at sowing, little of the 32P was recovered in the microbial biomass. Of the 33P applied in the medic residues, 22-28 percent was recovered in the microbial biomass. Most of the P taken up by the microbial biomass was derived from native soil P.
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