The book focusses on one of the most complex and difficult problems in subsurface flow: the transport of water and dissolved substances through unsaturated soils. The predominantly vertical flow in the unsaturated zone is governing the processes of groundwater recharge as well as the input of any kind of waterborn substances that may be transported from the surface through the unsaturated zone into the groundwater body. The book focusses on analyzing the transport of water and solutes in unsaturated-saturated porous media with special emphasis on macropore effects due to plant roots - a significant effect in agricultural areas. Another specific strength of the present book is to be seen in the fact that a unique set of relatively large soil column tests has been conducted in a field setup, in which the effect of decayed plant roots channels on solute transport processes was investigated. These intensive field tests and the new results derived from the experiments provide a significant step forward in our understanding and quantification of the role of macropores connected with plant root channels.