The Kitchawan soil was either not amended (K soil, which naturally contains predominantly kaolinite) or amended to 6% with montmorillonite (K6M soil) or to 3, 6, or 9% with kaolinite (K3K, K6K, or K9K soils). The SA soil naturally contains predominantly kaolinite, and the MOP soil contains predominantly montmorillonite. These soils and soil–clay mixtures have been used extensively in this laboratory in studies on the effects of various physicochemical factors on the activity, ecology, and population dynamics of microbes and viruses in soil, and therefore, there is a large data base available on them. Some of the physicochemical characteristics of these soils and soil–clay mixtures are shown in Table 1.