EFFECTS OF COPPER ON THE METABOLISM OF C-14-LABELED GLUCOSE IN SOIL IN RELATION TO AMENDMENT WITH ORGANIC MATERIALS

The effects of Cu on the mineralization of C-14-labeled glucose in soil and the incorporation of C-14 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 held-incubated soils to which C-14-labeled glucose was added were incubated for 28 d at 25 degrees C in the laboratory. While the Cu added to soil did not affect appreciably the mineralization of C-14-labeled glucose, the amendment with organic materials affected considerably the pattern of mineralization. On the other hand, the incorporation of C-14 into the soil microbial biomass was significantly inhibited by Cu addition. The inhibitory effect of Cu on the incorporation of C-14 was reduced by the amendment with organic materials, especially by the orchard grass amendment.