Agroscope, Institute for Plant Production Sciences IPS, 1260 Nyon, Switzerland

Microbial biomass in two arable soils

Over a two year period, changes in the microbiological properties of two arable soils were charted and compared with the site conditions. In the topsoil of a calcic cambisol, the content of microbial biomass was, on average, 42 % higher than in a gleyic cambisol. A higher pH and a looser strture favoured the development of microorganisms in the calcic cambisol. In the gleyic cambisol both an increase of the ground water level and high soil temperatures led to the loss of microbial biomass. Aridity and, thus, increased aeration of the soil encouraged the development of microbial biomass in the subsoil of both soil types. The measurements of metabolic activities all showed positive correlation with the microbial biomass in the soil, 75 % of which were significant.

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