Influence of soil moisture regime on the respiration response of soilssubjected to osmotic stress
The influence of the soil moisture regime on the tolerance of the soil micro-organisms to increased osmotic stress was examined by laboratory tests with a range of New Zealandsoils. Soils from various climatic regions (moist, intermediate and dry) were amended withglucose-NaCl solutions, incubated for 0-5 h, and the respiration rate over the following2 h was used as a measure of the response of the microbial biomass to the changedosmotic potential. Osmotic potentials were varied between -4 and -80 bar by altering theconcentration of NaCl. Air-drying the soils at 25“C decreased the respiration response of the microbial biomass by 3-60% but had little effect on the tolerance of the surviving populations to decreasedosmotic potentials. In general, the soils showed the same patterns: an osmotic potential of-23 bar decreased the respiration response by 28-45% (18-44% after air-drying) and a -80bar potential decreased it by 64-86% (52-84% after air-drying). For the majority of soils, a consistent relationship was obtained between the respiration rate of the moist soils and the osmotic potential applied. A reasonable prediction of therespiration response after air-drying could be obtained from the respiration response ofmoist soils at -25 bar osmotic potential. © 1989, CSIRO. All rights reserved.
Sparling, GP; West, AW; Reynolds, J
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