Introduction

This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book deals with soil biology, an area often ignored by scientists studying soil physical, chemical, and mineralogical factors in plant growth. It considers plant physiological aspects of root dynamics. Once a root occupies a volume of the soil, it affects and is affected by the microorganisms and mesofauna of that region. Thus, the root has an immediate effect on ecology of the soil. Roots excrete large amounts of photosynthate, and these organic compounds serve as substrate for microbial populations. Earthworms can have a major impact on plant rooting in the rhizosphere by their feeding, castings, and burrowing activities. No-tillage agricultural soils may be so permeated with burrows that surface water infiltrates rapidly and no surface runoff occurs.