Measurement of microbial biomass in rewetted air-dired soil by fumigation-incubation and fumigation-extraction techniques
1993
Zagal, E.
The quantity of microbial biomass was measured in a range of soils by the fumigation-incubation (FI) and fumigation extraction (FE) techniques. The air-dried soils were rewetted and incubated before the measurements were made. The FE method for biomass C was calibrated from the relationship between the flush of extractable organic C (Ec) and microbial-C, as estimated by the FI technique in the case of N, the size of the flush of total extractable N (EN) was compared to the flush of mineralization N (FN) by FI. Two different soils were chosen for further calibration by labelling (14C) microorganisms in situ (kEC factor). Biomass C (FE) accounted for 1% of soil C in the finer soils and only 0.4% of soil C in the coarser soils. Biomass content was related to soil texture, presumably because texture influences the ability of soils to preserve microbial biomass. The FI method appeared to underestimate biomass C (relative values) in the coarser soils. The FE technique gave higher biomass C estimates in these soils. The relationship between the flush (EC) and soil biomass C (FI) forced through zero was: biomass C = (2.42 +/- 0.164) Ec (r = 0.90). Somewhat different results were obtained when the FE method was calibrated by in situ labelling. A weaker relationship was obtained for the flush (EN) and the flush (FN) by FI (r = 0.80).
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