Effect of Labile Inorganic Phosphate Status and Organic Carbon Additions on the Microbial Uptake of Phosphorus in Soils

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, H 2 O, 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.