The Fundamental Studies on the Development of High Performance Soil

由于土壤通常位于室外，直接暴露在环境的影响下，很难人工控制土壤微生物的反应。我们着眼于人类对土壤的许多重要功能来自化学反应，特别是生物化学反应，而这些反应是由土壤微生物进行的。本研究首先从土壤化学的角度研究微生物生态，然后选择控制微生物生态或生存的因素。在掌握了这些知识后，我们开发了实验技术，通过应用微生境材料，例如微孔陶瓷作为土壤微生物的栖息地，在一定程度上控制土壤中的生物化学反应。通过这些试验，我们明确了微生物受化学和水分条件的强烈影响，并通过在底土中只埋高碳氮比的有机质，设计了一种防止旱地土壤硝酸盐淋失的实际应用技术。另一方面，建立了一种在土壤中建立接种细菌的成功方法。所使用的细菌菌株是鞘氨醇单胞菌SS86，它具有独特的需氧同化伽马-六氯环己烷的能力。众所周知，在简单接种到土壤中时，细菌会迅速消失，而每年使用伽马-六氯环己烷的土壤中的同化伽玛-六氯环己烷的少毛鞘氨醇单胞菌存活并建立。然而，SS86菌株被发现当被引入到在细菌接种之前暴露于伽马-六氯环己烷的土壤中时，该菌株在土壤中表现出与本土伽马-六氯环己烷同化少乳链球菌相同的动态。利用选择性底物是一种在土壤中建立接种菌的有效方法。

Since soils being located normaly in outdoors they are directly exposed to the influence of environment, it is very difficult to control artificially the reaction of soil microorganisms. We have focused to facts that many important functions which human being has expected for soils come from chemical reaction, especially bio-chemical one and that these reactions are carried out by soil microorganisms In this study we have started experiments firstly to examine the microbial ecology from the aspect of soil chemistry and then to select factors controlling the ecology or survival of microorganisms. Having acquired these knowledges, we have developed experimental technologies to control to some extent the bio-chemical reaction in soil by the application of the microhabitat materials, for example, micro-porous ceramics as a habitat for a soil microorganism. Through these experiments, we have clarified that microorganisms were strongly influenced by chemical and moisture conditions, and then, a practical application as a preventive technique of nitrate leaching in upland soil was devised by only burying organic materilas with high carbon-nitrogen ratio in subsoil. On the other hand, a succeeful method to establish an inoculated bacterium in soil was developed. The bacterial strain used was Sphingomonas paucimobilis SS86, which has a unique ability to aerobically assimilate gamma-HCH.The bacterium has been known to disappear rapidly when simply inoculated into soils, whereas the gamma-HCH-assimilating S.paucimobilis indigenous to the soil where gamma-HCH has been annualyly applied survives and becomes established. However, strain SS86 was found to establish itself when introduced into a soil which had been exposed to gamma-HCH before bacterial inoculation, showing the same dynamics in the soil as shown by the indigenous gamma-HCH assimilating S.paucimobilis. Use of a selective substrate was suggested to be a new method effective for establishing inoculated bacteria in soi