EFFECT OF LABILE INORGANIC PHOSPHATE STATUS AND ORGANIC CARBON ADDITIONS ON THE MICROBIAL UPTAKE OF PHOSPHORUS IN SOILS

Abstract

The effect of labile inorganic phosphate (P_i) status of the soil on the decomposition of added cellulose and on the immobilization, mineralization, and redistribution of native and added P in soils was studied in a greenhouse incubation experiment. Cellulose was added at 765 μg C∙g⁻¹ soil with and without P (9 μg∙g⁻¹ soil) every 30 days under adequate N, H₂O, and constant tempreature to two soils of different available P status. Lack of P eventually slowed down decomposition of added C, but this effect was partially compensated for by increased mineralization of organic P (P_o) forms. Added P was redistributed to both P, (58–69%) and P_o (42–31%) forms; higher amounts of P_o were found in the soil with the highest P_i status. The correlation between microbial P uptake and solution P values was significant, and microbial C:P ratios ranged from 12:1 under high available P conditions to 45:1 where P was in low supply.