Seasonal variations in soil S flush and possible contributions from plant roots in the measurement of soil microbial sulfur, phosphorus, potassium and nitrogen

Abstract

The seasonal changes of the flush of soil sulphur (S) after CHCl3 fumigation were studied in a two-year field trial on a high-producing pastoral soil. The pattern was different from that observed for microbial P, and this may be explained by seasonal changes in the contribution of roots to the soil S flush. Roots extracted from sieved (<4 mm) soil were used to estimate the contribution of plant roots in the determination of soil microbial P, K, N and S. Increases in P, K and N extracted from roots after CHCl3 fumigation made only a small contribution to the increases for the soil (4%, 2% and 7% for P, K and N respectively). The contribution of roots to the increase in S extracted from soil after fumigation was about 22%.