The rhizosphere is somewhat of an enigma and a challenge to soil and crop scientists as well as microbiologists. Although its definition—the zone of microbial stimulation under the influence of plant roots—is conceptually clear, a quantitative assessment of the spatial domain of the rhizosphere and its associated physico-chemical reactions, has yet to be achieved. Precise methods of determination of microbial numbers distributed within the root zone do not exist. The root environment is a complex, ever-changing ecosystem, enriched by the heterogeneous organic compounds exuded by roots, in both periodic and nonperiodic releases. Biotic interactions arising from these releases, as well as other plant and animal residues added to the soil, are difficult to ascertain. Yet, these interactions have profound effects within soil profiles and on crop production.
In this special publication, discussions focus on bacterial colonization of plant root systems, the interactions between microflora and soil fauna, the impact of the soil root interaction on plant nutrition, and an overview of the importance of microorganisms in the root zone. The authors, who are experts in their field, provide a lucid description of many processes apparent within the rhizosphere and a state of the art assessment of their importance in agronomy.
On behalf of the Societies, I express appreciation and thanks to the authors for preparation of the technical material; to the organizing and editorial committee members for conceptualizing and guiding the development of the publication; and to our Society Headquarters staff for technical editing and production.
Donald R. Nielsen, President
Soil Science Society of America
Plant productivity is regulated by microbial associations established with the plant system. The interactions of microorganisms and plant roots are especially important in providing nutritional requirements for the plant and for the associated microorganisms. This special interdisciplinary publication, Microbial-Plant Interactions, was developed from a symposium presented at the annual meeting of the Soil Science Society of America, American Society of Agronomy, and the Crop Science Society of America in Fort Collins, Colo. in 1979.
Specific areas addressed include: bacterial colonization, protozoa and nematodes in nutrient cycling, mycorrhizae, and an overview of rhizosphere microorganisms.
It is hoped these papers prepared by scientists in the fields of ecology, microbiology, and soil science will stimulate increased cooperation between these disciplines.
Appreciation is expressed to the authors and reviewers of these manuscripts for their patience and support. The American Society of Agronomy Headquarters Staff is to be recognized for their dedicated efforts in making this publication possible.
R. L. Todd
J. E. Giddens