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United States Department of Agriculture

Agricultural Research Service


item Smith, Jeffrey
item Collins, Harold - Hal

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 4/1/2006
Publication Date: 4/1/2007
Citation: Smith, J.L., Collins, H.P. Managing soil microorganisms and their processes. Book Chapter pp 471-502. 2007.

Interpretive Summary: Soil microorganisms are important in ecosystem development and sustainability since they are responsible for processing any material introduced to the system. In natural ecosystems introduced material would simply be litter from growing vegetation, however, in managed ecosystems such as agricultural soils inputs could be organic material and synthetics such as fertilizer. In addition, in contaminated systems inputs could be toxic wastes such as petroleum products. In any soil system it would be of interest to be able to manage soil microorganisms to man's benefit be it helping plants grow or cleaning up toxic waste. There are numerous examples of man's manipulation of organisms, such as in wine and cheese production and the development of antibiotics. In this article we explore ways in which soil microorganism are manipulated and ways in which we may be able to manipulate them in the future to increase crop yields, increase fertilizer use efficiency and decrease toxic chemical load to the environment.

Technical Abstract: In natural systems organisms can be structured compartmentally to be, close to other organism for symbiosis, away from other organisms for protection and in proximity to nutrients and water. An example of organism symbiosis is fungi breaking down the macromolecule cellulose into smaller more 'digestible' compounds that can be utilized by other bacteria and fungi that can't utilize cellulose directly. In addition, an organism may need a specific growth factor or vitamin that may be produced by specific bacteria, thus growing in a mixed culture (soil) the first organism receives 'nutritional symbiosis'. There is however a downside to living among a myriad of different organisms, that is some are predators and some will resort to predation to survive. Predation is probably the biggest factor in organism composition changes over time. When carbon inputs from litter reach the soil, bacteria increase in numbers, then bacterial feeding protozoa increase and a new short equilibrium will be reached in community composition. These cyclic fluxion in population structure drive the complex food web system of the soil and dictate nutrient availability to plants. From this perspective perhaps it is the soil microflora that are doing the 'managing' in many ecosystems. We will discuss these types of interactions in the context of managing microorganisms.

Last Modified: 08/19/2017
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