Effects of copper on the metabolism of14C-labeled glucose in soil in relation to amendment with organic materials

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Abstract
The effects of Cu on the mineralization of 14C-labeled glucose in soil and the incorporation of 14C into the soil microbial biomass were investigated in a laboratory experiment in relation to the amendment with organic materials. Samples from a Brown Lowland soil (Udifluvent), which was amended with farmyard manure or orchard grass at the rate of 20 g kg-1 soil and/or enriched with 2,000 mg kg-1 soil of Cu, were incubated for 14 weeks under field conditions. The amounts of microbial biomass C and biomass ninhydrin-N in the field-incubated soils were significantly reduced by the addition of Cu regardless of the amendment with organic materials. The field-incubated soils to which 14C-labeled glucose was added were incubated for 28 d at 25°C in the laboratory. While the Cu added to soil did not affect appreciably the mineralization of 14C-labeled glucose, the amendment with organic materials affected considerably the pattern of mineralization. On the other hand, the incorporation of 14C into the soil microbial biomass was significantly inhibited by Cu addition. The inhibitory effect of Cu on the incorporation of 14C was reduced by the amendment with organic materials, especially by the orchard grass amendment.