Assessing plant-microbial competition for P-33 using uptake into phospholipids

A novel method of estimating soil microbial P uptake, using P-33 incorporation into the phospholipids in soil microbial biomass, was used in a study of P-competition between plants and microorganisms. The microbial biomass, and thus the competition for the added P-33, was altered by using different glucose treatments in a microcosm set-up. There was obvious competition for P-33, as shown by the negative relationship between P-33 uptake by the plant and P-33 incorporation into microbial phospholipids. The data thus indicate that soil microorganisms partly control P-33 uptake by the plant. The suggested method of measuring P-33 in phospholipids appears to have the potential to provide a rapid alternative to techniques such as chloroform fumigation-extraction for the determination of microbial P uptake, although at present the method will only give relative estimates of P uptake.