著者

Aoyama Masakazu Nagumo Toshiyuki

出版者

一般社団法人日本土壌肥料学会

雑誌

Soil science and plant nutrition (ISSN:00380768)

巻号頁・発行日

vol.42, no.4, pp.821-831, 1996-12

被引用文献数

2

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The size of the microbial biomass and dehydrogenase activity were measured in air-dried and rewetted apple orchard surface soils with accumulation of Cu, Pb, and As due to the application of Bordeaux mixtures and lead arsenate. The largest amounts of total Cu, Pb, and As found in the soils used were 1, 108, 1, 271, and 209 mg kg^<-1> soil, respectively. The amounts of 0.1 M HCl-extractable heavy metals were strongly correlated with the total amounts, while those of 0.1 M CaCl_2-extractable heavy metals, except for As, increased significantly with decreasing soil pH. The amounts of microbial biomass C and N, expressed on a soil organic C and total N basis, respectively, were each negatively correlated with the amounts of total and 0.1 M HCl-extractable Cu. On the other hand, the dehydrogenase activity was not affected by the amounts of total and 0.1 M HCl-extractable heavy metals, and was negatively correlated with the amount of 0.1 M CaCl_2-extractable Cu and positively with the soil pH. Higher significant correlations were observed when the dehydrogenase activity was calculated per unit of soil organic C. Thus the microbial biomass was adversely affected by the slightly soluble fractions of Cu accumulated in apple orchard soils, whereas the dehydrogenase activity was affected by the water-soluble and exchangeable Cu of which amount depended on the soil pH. It is suggested that the microbial biomass and dehydrogenase activity expressed on a soil organic matter basis could become useful indicators for assessing the effects of heavy metals on the size and activity of the microbial biomass in soils differing in organic matter contents