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The kinetics of glucose uptake by soil microbial communities in 16 different soild (7 under monocultures and 9 under crop rotations) differing in microbial biomass content, % Corg, pH and clay content were investigated at 22°C. The Vmax value of microbial bimasses under monoculture, was o.27 μg Cgluc · μg−1 Cmic · h−1 (range 0.18–0.44), twice as high as the mean value of Vmax of microbial biomasses under rotations (0.13 μg Cgluc, range 0.07–0.19). Mean values of Km were 714 μg Cgluc and 290 μg Cgluc · g−1 soil, respectively. These differences were highly significant (P=0.001, based on SE) and could not be relate to particle size distribution of the soils, pH or Corg. A Michaelis-Menten type uptake response was apparent over the total range of glucose concentrations used (45.4–1453.3 μg Cgluc · g−1 soil) for microbial biomasses under rotation while the majority of microbial biomasses under monocultures showed a similar response only at low glucose concentrations. A different uptake mechanism appeared to be involved at higher glucose concentrations (similar to diffusion) in monoculture soils. |
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