Soil Research Soil Research Society
Soil, land care and environmental research

A dual radiotracer study of transformations of organic, inorganic and plant residue phosphorus in soil in the presence and absence of plants

DK Friesen and GJ Blair

Australian Journal of Soil Research 26(2) 355 - 366
Published: 1988


The rates of transfer of P from plant residues added to an acid soil into various soil P pools and the rates of transfer of inorganic P from soil solution into other soil P pools were studied by simultaneous use of 32P-labelled plant matter and 33P-labelled soil in the presence and absence of growing plants. Equilibration of 33P-labelled phosphate solution added to soil reached a steady state with soil ALP and Fe-P pools within 1 day after addition. The Fe-P pool was much more stable than the A1-P pool since it was not depleted by cropping. This non-labile pool 'fixed' over 30% of the 33P added and similar amounts of the 32P released from plant residues. About 50% of the 32P from plant residues was found in inorganic P pools 11 days after addition. This rapid release was attributed to the presence of soluble inorganic P in the residues. A further 10% was released slowly over the remainder of the experiment. Cropping only marginally slowed rates of transfer of inorganic and released residue P into non-labile pools. Cropping had no effect on the rates of release of P from crop residues.

© CSIRO 1988

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