Abstract
We measured the amount of microbial biomass and some physicochemical properties of 9 volcanic ash soils and 7 non-volcanic ash soils in Japan and analyzed their relationships. The results obtained are as follows : 1) The amounts of biomass C and N did not significantly differ between the volcanic (58-1504 mgC kg^<-1>, 10-180 mgN kg^<-1>) and non-volcanic ash soils (11-1118 mgC kg^<-1>, 2-124 mgN kg^<-1>). 2) Both in volcanic and non-volcanic ash soils, the amounts of biomass C and N showed significant relationships (r≧0.826^*, n=7) with organic C content, total N content, total humus content, NaOH-extracted humic acid content, NaOH-extracted fulvic acid content and Al_2O_3 content. The relationships between the amounts of biomass C and N and the CEC and phosphate absorption coefficient were significant (r≧0.809^<**>, n=9) only in volcanic ash soils, and the relationship between the amount of biomass and clay content was significant (r≧0.839^*, n=7) in non-volcanic ash soils. The soil characteristics having significant relationships (r≧0.902^<**>, n=9) with the amount of biomass also showed significant relationships (r≧0.827^*, n=7) with fulvic acids, total humus, humic acids or organic C contents. 3) The relationships between the amounts of biomass C and N and several soil characteristics such as organic C, total N, total humus, fulvic acids, humic acid content, CEC, phosphate absorption coefficient and Al_O_3 content can be separated into two groups: volcanic ash soil group and non-volcanic ash soil group.
