Compost, rapeseed rotation, and biocontrol agents significantly impact soil microbial communities in organic and conventional potato production systems

Authors: BERNARD, EDWARD - University Of Maine; Larkin, Robert - Bob; TAVANTZIS, STELLOS - University Of Maine; ERICH, M. SUSAN - University Of Maine; ALYOKHIN, ANDREI - University Of Maine; LANNAN, ANDREW - University Of Maine; GROSS, SERENA - University Of Maine

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2011
Publication Date: 11/10/2011
Citation: Bernard, E., Larkin, R.P., Tavantzis, S., Erich, M., Alyokhin, A., Lannan, A., Gross, S. 2011. Compost, rapeseed rotation, and biocontrol agents significantly impact soil microbial communities in organic and conventional potato production systems. Applied Soil Ecology. 52:29-41.

Interpretive Summary: Cultural practices such as organic amendments, rotations, and use of biological control organisms are regularly investigated for their effects on controlling plant diseases but their effects on soil microbial populations, which may be very important for understanding and managing long-term effects, are often unexplored. In this study, three different sustainable disease management practices, use of compost amendment, biocontrol organisms, and a potentially disease-suppressive rapeseed rotation, were established in potato field trials at two sites under different management regimes and histories (conventional vs. organic production practices), and evaluated over three potato cropping seasons for their effects on soil microbial communities. All treatments had significant effects on soil microbial community characteristics, but compost amendment and rapeseed rotation had substantially greater effects than biocontrol organisms, and resulted in higher microbial populations and significant shifts in soil microbial community composition. Combined effects of multiple treatments were generally complementary, suggesting the potential of combining multiple compatible management practices and their associated changes in soil microbial communities for improved disease and soil management. This research is of interest to scientists, extension personnel, and growers, providing useful information on the development of sustainable disease management systems.

Technical Abstract: In this study, three different sustainable disease management practices were evaluated in potato field trials at two sites under different management regimes (organic vs. conventional production) over three potato cropping seasons for their effects on soil microbial communities. Management factors assessed included the presence or absence of a conifer-based compost amendment, addition of one of three different biocontrol organisms (Trichoderma virens, Bacillus subtilis, and Rhizoctonia solani isolate Rhs1A1), and a rapeseed green manure rotation crop preceding potato. Compost amendment and rapeseed rotation had the greatest impacts on soil microbial communities, with both treatments increasing populations of culturable bacteria at both sites, as well as causing detectable shifts in soil microbial community characteristics as determined by sole carbon-source substrate utilization and fatty acid methyl ester (FAME) profiles. Compost amendment generally led to increased utilization of complex substrates and increased levels of Gram-positive bacteria and fungi, and effects were more pronounced at the conventional site. Rapeseed rotation often resulted in somewhat different effects at the two sites. Effects of the biocontrol amendments Rhs1A1 and T. virens were smaller, but included increased microbial activity and bacterial populations. Combined effects of multiple treatments were greater than those of individual treatments and were generally additive. These results indicate that each treatment factor had significant and specific effects on soil microbial communities, and that combined effects tended to be complementary, suggesting the potential of combining multiple compatible management practices and their associated changes in soil microbial communities.