ARS | Publication request: A systems approach for enhancing soil quality and plant health under organic and conventional conditions: Effects on Soil Microbial Communities

Submitted to: Northeast Potato Technology Forum
Publication Type: Proceedings
Publication Acceptance Date: March 2, 2009
Publication Date: March 6, 2009
Citation: Bernard, E., Larkin, R.P., Erich, M., Alyokhin, A., Gross, S., Tavantzis, S. 2009. A systems approach for enhancing soil quality and plant health under organic and conventional conditions: Effects on Soil Microbial Communities. Northeast Potato Technology Forum Proceedings. p. 13.

Technical Abstract: In the second year of an integrated agricultural systems project, research plots established at both organic and conventional farm sites were sampled to assess soil microbial population dynamics in response to biocontrol and compost amendment, as well as with a rapeseed rotation. Compost amendment produced significant changes in microbial population parameters at both sites at summer and fall sampling dates. Significant increases (25 to 80%) in bacterial and fungal colony forming units (CFUs) and overall microbial activity were found in composted plots compared to non-composted plots. This effect was more pronounced at the conventional site. Similarly, amendment with a hypovirulent Rhizoctonia solani isolate was associated with significantly higher bacterial CFUs and, when in combination with compost, higher fungal CFUs and microbial activity. Trichoderma virens-amended plots were also associated with increased bacterial and fungal CFUs, while plots amended with Bacillus subtilis demonstrated significantly lower overall microbial activity and fungal numbers than other treatments. The previous rapeseed rotation or barley rotation had significant but variable effects on most microbial parameters. In addition, fatty acid methyl ester profiles strongly delineated compost and biocontrol effects within the rotation crop. Fungal fatty acids were often enriched in plots that followed rapeseed rotation. Specific bacterial fatty acids, in contrast, were more strongly associated with plots that followed barley rotation. These results indicated that all three factors (compost amendment, biocontrols, and rapeseed rotation) had specific and distinctive effects on soil microbial communities, and that these changes may be related to differences in disease development.