In soil, net immobilization of Carbon and Phosphorus occurs when the C:P ratio is:

A. < 200 : 1
B. > 300 : 1
C. 200–400 : 1
D. 200–300 : 1
E. < 20 : 1

Key Notes

Net immobilization of phosphorus occurs when organic residues have a high C:P ratio, typically between 200–400:1, causing soil microorganisms to utilize available soil phosphorus for their growth. This reduces phosphorus availability to plants until decomposition progresses and mineralization begins.