クロタラリアの葉や茎,バーク堆肥,牛ふん堆肥を添加した土壌および無添加土壌の培養試験を行い,微生物バイオマス(以下:バイオマス)とバイオマス当たりの呼吸活性(以下:呼吸活性)の経時変化を調査した。有機物の種類は土壌微生物特性に強く影響した。バイオマスは有機物添加で増加するが,その程度はクロタラリア葉区で特に大きく,施用1日後に乾土当たり1700mg C kg^<-1>に達した。次いでクロタラリア茎区,牛ふん堆肥区であり,バーク堆肥区は有機物無添加区レベルであった。呼吸活性は,クロタラリア葉区および同茎区で初期に高まったが,15日後には有機物無添加区に近いレベルまで漸減した。バーク堆肥区は培養期間を通じて有機物無添加区レベルであった。これらのことより,本試験で用いた有機物は主としてバイオマスを増大させる有機物と,バイオマスと呼吸活性の両者を増大させる有機物,またそれらのいずれをもほとんど増大させない有機物とに区分できることが明らかになった。
The Kanagawa Agricultural Technology Center has been testing the effect of a compost consisting of okara and coffee residue (OC) on Japanese radish cultivation since 1996. It is known that damage by the root-lesion nematode to Japanese radish was less severe in OC-soil than in a soil amended with cow manure compost (CM). In this study, the effects of amendment with OC-compost on soil communities of nematodes and microbes were investigated and compared with those of amendment with CM and chemical fertilizer (CF) in 2006 and 2007. There were no significant differences in total carbon among the three soils, but the soil microbial biomass was significantly higher (ca. 2.5 times) in OC- and CM-soils than in CF-soil. Glucose decomposing activity was the highest in OC-soil, followed by CM-soil and then CF-soil. There was no significant difference in the density of the root-lesion nematode, but that of free-living nematodes was significantly higher in OC- and CM-soils than in CF-soil. The community structures of nematodes and fungi in the soils and of bacteria on the Japanese radish surface, as analyzed by PCR-DGGE, were different among the three soils in both years, while the soil bacterial community was not different. Unique bands were detected in OC- and CM-soils in most of the DGGE profiles, suggesting enrichment of specific microbes and nematodes by the organic matter application. Collectively, amendment with OC- and CM-compost increased the soil microbial activity and biomass and affected the soil microbial and nematode community structures. OC-compost increased the soil microbial activity more than CM-compost did.