This volume is the first publication of its kind to provide a fully comprehensive and detailed approach to the survey of microbial associations in soil: their structure and function in relation to soil fertility and environment protection. The problems covered by this title are presented on various levels of the ecological system; from subcellular phenomena occurring in the microbial cell (genetic and enzyme regulation), to processes taking place in the flow of mass and energy in the agroecosystem. The aim of this monograph is to contribute to the understanding of the laws of formation and function of microbial associations in natural and agricultural soils, and to build a scientific basis for the control of soil biological processes. Using a contemporary approach to some fields of soil microbiology, the book highlights the possibility of utilizing certain microorganisms and microbial processes to increase soil fertility and protect the environment. These critically evaluated and selected results were obtained at the Institute of Microbiology and the Institute of Experimental Phytotechnics of the Czechoslovak Academy of Sciences, in cooperation with the Institute of Microbiology of the Academy of Sciences of the USSR.