My research focuses on physical processes in the unsaturated (vadose) zone, in the basic theory of flow and application of the theory to environmental problems. I am also interested in biological processes in soil associated with physical properties. I have numbers of publications in the topic of biological clogging, or bioclogging, of soil pores by microbes, and these publications are frequently cited. I also published several papers related to environmental problems in soil. The topics include alkalinization of soil, contamination of soil by fallout radiocesium and strontium, physical and chemical properties of soil affected by forest fire, and remediation of soil with biobarrier technique.