ABSTRACT
Plants absorb nutrients and moisture from soil through their root systems. As soil consists of minerals, organic matter, air, and water, it acts not only as a medium for plant growth but also as a home for numerous microbes. When plants grow in soil they also release a wide range of organic compounds. These substances and sloughed-off root tissues attract millions of microbes around the root zone of plants and create a region of vigorous microbial activity. There are millions of tiny bacteria, actinomycetes, yeast, protozoa, and fungi in each gram of soil. Among the microorganisms that reside in soil, bacteria are found to be the most abundant groups both in number and variety. Over 1 billion bacteria may be contained in 1 gram of fertile topsoil. They live on the roots of plants or in the volume of soil that is adjacent to and influenced by the plant roots (rhizosphere). These microbes interact with plants’ roots and the nutrients in the soil. Some of them have no effect on plants, but others have either beneficial or detrimental effects. Utilization of these interactions by soil microbiologists and biotechnologists has resulted in renewed interest in the use of microbial inoculants in agriculture, forestry, and environmental management. Use of microbial inoculants (biofertilizers, phytostimulators, and biopesticides) as a strategy to ensure competitive yields and protection of crops in agriculture represents an attractive and environmentally friendly alternative to further applications of synthetic fertilizers and chemical pesticides. This method of farming, often referred to as sustainable agriculture, seeks agricultural practices that are proenvironment for maintaining the long-lasting ecological equilibrium of the soil system and ultimately beneficial to human health (see Figure 6.1).
