Progress 07/01/07 to 06/30/12

Outputs
OUTPUTS: The overall goal was to improve crop production through integration of sustainable practices promoting soil regeneration, reduction of disease pressure, and enhancement of plant growth. Soil properties, soilborne disease levels, potato yields, and soil microbial communities were assessed on an organic farm and a conventional farm following various soil amendments. Specific management factors assessed included a conifer-based compost amendment, one of three different biocontrol organisms (Trichoderma virens, Bacillus subtilis, and Rhizoctonia solani isolate Rhs1A1), and a rapeseed green manure rotation crop preceding potato, and treatments were assessed in all factorial combinations. Compost amendment and rapeseed rotation had the greatest impacts on soil microbial communities, with both treatments increasing total populations of culturable bacteria at both sites over the course of the study, as well as causing shifts in soil microbial community characteristics as determined by sole carbon-source substrate utilization and fatty acid methyl ester (FAME) profiles. Compost amendment resulted in increased utilization of complex substrates and increased levels of Gram-positive bacteria and fungi, and compost effects were more pronounced at the conventional site. Rapeseed rotation often resulted in somewhat different effects at the two sites. Consistent overall effects were observed with the biocontrol amendments Rhs1A1 and T. virens, including increased microbial activity and bacterial populations. Combined effects of multiple treatments were greater than those of individual treatments and were generally additive. Each treatment had significant and specific effects on soil microbial communities, and combined treatment effects tended to be complementary, suggesting the potential for combining multiple compatible management practices and their associated changes in soil microbial communities. Rapeseed rotation had the greatest effects on disease suppression, reducing all observed soilborne diseases (stem canker, black scurf, common scab, and silver scurf) by 10 to 52% in at least one year at both sites. Compost amendment had variable effects on tuber diseases, but consistently increased yield (by 9 to 15%) in all years at the conventional site and in two of three years at the organic site. Biocontrol effects on disease varied, though Rhs1A1 decreased both incidence and severity of black scurf at the conventional site in two out of three years, and T. virens reduced multiple diseases at the organic site in at least one year. The above treatments alone, and in combination were effective at reducing disease and increasing yield under both conventional and organic production practices. A method involving removal of organic matter inhibitors from soil DNA samples and qPCR for the detection of R. solani AG-3 was developed to detect and quantify pathogen populations in cultivated potato soils, under commercial field conditions over the course of three years. The amount of R. solani ranged from 400 to 243,100 copies of the AG-3 ITS 1 and 2 rDNA gene per gram of soil, demonstrating a large variability in population density both spatially and temporally. PARTICIPANTS: Dr. Edward Bernard, supported by this project as a doctoral candidate, completed the experiments of this project in this past year and received his Ph. D. degree. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
As a result of this project, agricultural scientists and growers (in Maine and elsewhere) have access to improved knowledge on important parameters related to holistic, sustainable approaches to crop production, especially in regards to appreciation of the complexity of the agro-ecosystem as well as the expected range and degree of benefits resulting from particular soil amendments or combinations thereof. More organic growers are expected to use biocontrol and mutualistic microorganisms to improve plant disease management, enhance crop yields, and increase soil fertility, and this will lead to an improved abundance of healthier, locally grown, food for consumers, and higher incomes, through higher product value, for Maine growers. Finally, implementation of the strategies described in this project is expected to result in a reduced rate of environmental pollution through a decreased use of synthetic agrichemicals. The data of this project have been reported at several forums such as organic grower trade shows, regional technology meetings, and national scientific meetings. We have also given a presentation of our findings to national representatives of the Organic Seed Alliance. Finally, the owner (Mr. Jim Gerritsen) of Wood Prairie Farm on which we conducted part of our study, is an international leader in organic farming, so our findings are disseminated to other organic farmers in many parts of the country and the world.

Publications

• Edward Bernard, Robert P. Larkin, Stellos Tavantzis, M. Susan Erich, Andrei Alyokhin, and Serena D. Gross. 2012. Evaluation of Several Different Management Practices on Soil-borne Diseases and Tuber Yield in Organic and Conventional Potato Production Systems. Applied Soil Ecology (In Review).
• Edward Bernard, Stellos Tavantzis, Kristopher Cooper, Andrei Alyohkin. 2012. Monitoring Rhizoctonia solani AG-3 Levels in Response to Disease-Suppressive Management Practices. Plant Disease (In Review).
• Bernard, E., Larkin, R. P., Tavantzis, S. M., Erich, M. S., Alyokhin, A., Sewell, G., Lannan, A., and S. D. Gross. 2012. Compost, rapeseed rotation, and biocontrol agents significantly impact soil microbial communities in organic and conventional potato production systems. Applied Soil Ecology 52:29-41.
• Edward Bernard, Robert P. Larkin, A. Alyokhin, M.S. Erich and Stellos Tavantzis. 2012. From Soil to Symptoms: Investigating the Link Between Pathogen Population and Disease. Northeast Potato Technology Forum, 2012 Proceedings (p. 9).

Progress 07/01/10 to 06/30/11

Outputs
OUTPUTS: The field portion of this project was conducted from 2007-2009 to assess the impact of various soil amendments on potato disease suppression and soil microbial community characteristics. This portion of the project was designed to investigate the association between specific pathogen levels for Rhizoctonia solani in soil from the different treatments and black scurf (caused by R. solani). In order to achieve this goal, DNA was extracted from soil samples which had been collected in the summer and fall of each year of the field study. Quantitative polymerase chain reaction (qPCR) was then used to detect the amount of R. solani DNA in composite soil samples representing each treatment. Results of qPCR showed that R. solani was detected in almost all soil DNA samples from each season of each year. Levels of R. solani DNA were comparable among soils receiving different soil amendments. While there were many significant differences in the levels of R. solani DNA detected among treatments, these effects were often not observed in more than one year or more than one season. Correlation analysis revealed that there was no overall correlation between the levels of R. solani DNA detected in the summer and fall samplings (of the same treatment). However, there was an overall correlation between the levels of R. solani DNA in soils collected from the summer sampling and severity and incidence of black scurf on tubers, demonstrating that levels of R. solani DNA in the soil in the midst of the growing season are roughly indicative of the disease observed in the fall (at harvest). Of the treatments used in the study, compost amendment resulted in slight increases in the severity (less than 0.5% increase in average overall surface area coverage) of black scurf disease in two of the three years. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: A final no-cost extension was awarded to allow us completion of the experiments related to the association between the amount of soil-borne pathogen population, as determined by qPCR, and disease incidence and severity.

Impacts
This is an ongoing three-year field study with a vast database, which is currently analyzed, with more data, related to soil-borne pathogen population assessment (by qPCR) as it relates to disease incidence and severity, still being generated. Resources (provided through this grant) have enabled us to conduct one of the most thorough field/laboratory studies reported to date. A refereed article is currently in press in a major soil ecology journal. When all aspects of this complex project are carefully considered, final conclusions and recommendations to the agricultural and ecological communities will be made.

Publications

• Edward Bernard, Robert P. Larkin, Stellos Tavantzis, M. Susan Erich, Andrei Alyokhin, Gary Sewell, Andrew Lannan, and Serena D. Gross. 2011. Compost, Rapeseed Rotation, and Biocontrol Agents Significantly Impact Soil Microbial Communities in Organic and Conventional Potato Production Systems. Applied Soil Ecology. In press.

Progress 07/01/09 to 06/30/10

Outputs
OUTPUTS: All of the experiments outlined in the grant proposal for the third year of the project were completed at the organic site Wood Prairie Farm (Bridgewater, Maine) and the various labs on the University of Maine campus. The data was presented at an organic grower trade show in Augusta, Maine, the more technical Northeast Potato Technology Forum, and at national meetings such as National Society of Agronomy, and Entomological Society of America. PARTICIPANTS: Stellos Tavantzis, Project Director, a plant pathology professor at UMaine, was administrator and overall coordinator of the d project. He conducted all communications regarding field operations, was involved in all field operations, and coordinated interactions with the Grower Advisory Committee, and data presentations within the group. Robert Larkin, co-PD, a senior scientist at New England Plant, Soil and Water Research Laboratory, and faculty associate in the Department of Plant, Soil and Environmental Sciences at UMaine, supervised most field operations including experimental design, planting, disease assessment, plant and soil sample collection and analysis. Andrei Alyokhin, co-PD, an applied entomology associate professor at UMaine, was in charge of sampling and analyzing insect populations and assessing insect damage on crops. Susan Erich, co-PI, a soil chemistry professor at UMaine, was in charge of all aspects of soil analyses related to fertility and physical properties. John Jemison, co-PI, an Extension Professor for the UMaine Cooperative Extension, is in charge of outreach efforts as they relate to dissemination of our data to conventional and organic growers using his Cooperative Extension network and experience. He attended data presentation meetings but was not involved in data dissemination since we only had one year of data. Eric Sideman, collaborator, Director of Technical Services/Crop Specialist of the Maine Organic Farmers and Gardeners Association (MOFGA) was the coordinator of the Grower Advisory Committee, and facilitated our presentations to organic growers at the 67th Augusta Trades Show. Edward Bernard, a Ph. D. candidate supported by the project, assisted in all field operations, conducted all soil microbiological analyses (fatty acids, BIOLOG, etc.), data analyses, and data presentation. Serena Gross, and Andrew Lannan M. S. graduate students, supported by the project, assisted in all field operations, was involved in insect sampling, assessing insect damage, soil analysis, data analysis, and other ad hoc tasks. Several undergraduate students were hired to help with field operations and laboratory work (soil and microbial analyses, and soil DNA extractions). TARGET AUDIENCES: As indicated above, presentations have been made at trade, professional and scientific meetings. PROJECT MODIFICATIONS: Soil DNA extractions and QPCR experiments were postponed due to lack of additional personnel but are currently being conducted by existing personnel.

Impacts
This is an ongoing three-year field study with a vast database, which is currently analyzed, with more data, related to soil-borne pathogen population assessment (by QPCR) as it relates to disease severity and yields, still being generated. Resources (provided through this grant) have enabled us to conduct one of the most thorough field/laboratory studies reported to date. When all aspects of this complex project are carefully considered, final conclusions and recommendations to the agricultural and ecological communities will be made.

Publications

• Serena D. Gross, Andrei Alyokhin, Robert Larkin, M. Susan Erich, Edward Bernard and Stellos M. Tavantzis. 2010. Response of Insect Herbivores to Disease-Suppressive Soil Amendments in Potato. Agriculture, Ecosystems, and Environment (submitted).
• M. Susan Erich, Stellos Tavantzis, Robert Larkin, Andrei Alyokhin, Andrew Lannan, Serena D. Gross, and Edward Bernard. 2010. Effects of Organic Disease Suppression Strategies on Soil Properties in Organic and Conventionally Managed Potatoes. Agriculture, Ecosystems, and Environment (submitted).

Progress 07/01/08 to 06/30/09

Outputs
OUTPUTS: The experiments described (in the grant proposal) for the second year of the grant were completed at the organic Wood Prairie Farm (Bridgewater, Maine). The data was analyzed and reported at forums such as an organic grower trade show (in Augusta, Maine), a more technical professional meeting (Bangor, Maine), and national meetings (please see below). We have not been involved in field days or training events to date, although we plan to do so, when we reach our final conclusions upon completion of the project. PARTICIPANTS: Stellos Tavantzis, Project Director, a plant pathology professor at UMaine, was administrator and overall coordinator of the d project. He conducted all communications regarding field operations, was involved in all field operations, and coordinated interactions with the Grower Advisory Committee, and data presentations within the group. Robert Larkin, co-PD, a senior scientist at New England Plant, Soil and Water Research Laboratory, and faculty associate in the Department of Plant, Soil and Environmental Sciences at UMaine, supervised most field operations including experimental design, planting, disease assessment, plant and soil sample collection and analysis. Andrei Alyokhin, co-PD, an applied entomology associate professor at UMaine, was in charge of sampling and analyzing insect populations and assessing insect damage on crops. Susan Erich, co-PI, a soil chemistry professor at UMaine, was in charge of all aspects of soil analyses related to fertility and physical properties. John Jemison, co-PI, an Extension Professor for the UMaine Cooperative Extension, is in charge of outreach efforts as they relate to dissemination of our data to conventional and organic growers using his Cooperative Extension network and experience. He attended data presentation meetings but was not involved in data dissemination since we only had one year of data. Eric Sideman, collaborator, Director of Technical Services/Crop Specialist of the Maine Organic Farmers and Gardeners Association (MOFGA) was the coordinator of the Grower Advisory Committee, and facilitated our presentations to organic growers at the 67th Augusta Trades Show. Edward Bernard, a Ph. D. candidate supported by the project, assisted in all field operations, conducted all soil microbiological analyses (fatty acids, BIOLOG, etc.), data analyses, and data presentation. Serena Gross, and Andrew Lannan M. S. graduate students, supported by the project, assisted in all field operations, was involved in insect sampling, assessing insect damage, soil analysis, data analysis, and other ad hoc tasks. Kylie Palmer, Kristopher Cook, both undergraduate students, were hired to help with field operations and laboratory work (soil and microbial analyses). Peter Gerritsen, son of Wood Prairie Farm owner Jim Gerritsen, was employed part-time during the summer to help with field operations and sample collections. TARGET AUDIENCES: First- and second-year data was presented at trade, professional and scientific meetings (see presentations above). PROJECT MODIFICATIONS: As described in the grant proposal, the rapeseed cover crop was included in this second year of the project.

Impacts
We have had two significantly different (weather-wise) growing seasons in the first two years of the study. A third season (currently ongoing) would be necessary for us to start making relatively reliable observations and conclusions.

Publications

• Tavantzis, S., Larkin, R.P., Erich, S., Bernard, E., Gross, S., and Alyokhin, A. 2009. A Systems Approach for Enhancing Soil Quality and Plant Health under Organic and Conventional Conditions (Abstract). Northeast Potato Technology Forum. Bangor, Maine.
• Larkin, R.P., Tavantzis, S., Erich, S., Bernard, E., Gross, S., and Alyokhin, A. 2009. A Systems Approach for Enhancing Soil Quality and Plant Health under Organic and Conventional Conditions: Effects on Soilborne Diseases and Tuber Yield (Abstract). Northeast Potato Technology Forum. Bangor, Maine.
• Gross, S., A. Alyokhin, R. Larkin, S. Erich and S. Tavantzis. 2009. Reduced pest insect densities following compost application in organic and conventional systems (Abstract). Northeast Potato Technology Forum. Bangor, Maine.
• Bernard, E., Larkin, R.P., Erich, S., 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 (Abstract). Northeast Potato Technology Forum. Bangor, Maine.

Progress 07/01/07 to 06/30/08

Outputs
OUTPUTS: All of the experiments described in the respective grant proposal for the first year of the grant were completed, the data analyzed and reported at forums such as organic grower trade shows, more technical technology meetings, and national meetings (please see below). More than ten reports were presented in these meetings. We have also given a presentation of our findings to national representatives of the Organic Seed Alliance. Since the data were based on single-year observations, we were not involved in field days or training evens. However, the owner of Wood Prairie Farm on which we are conducting our study, is an international leader in organic farming, our findings are disseminated in an unofficial manner to other organic farmers. PARTICIPANTS: Stellos Tavantzis, Project Director, a plant pathology professor at UMaine, was administrator and overall coordinator of the d project. He conducted all communications regarding field operations, was involved in all field operations, and coordinated interactions with the Grower Advisory Committee, and data presentations within the group. Robert Larkin, co-PD, a senior scientist at New England Plant, Soil and Water Research Laboratory, and faculty associate in the Department of Plant, Soil and Environmental Sciences at UMaine, supervised most field operations including experimental design, planting, disease assessment, plant and soil sample collection and analysis. Andrei Alyokhin, co-PD, an applied entomology associate professor at UMaine, was in charge of sampling and analyzing insect populations and assessing insect damage on crops. Susan Erich, co-PI, a soil chemistry professor at UMaine, was in charge of all aspects of soil analyses related to fertility and physical properties. John Jemison, co-PI, an Extension Professor for the UMaine Cooperative Extension, is in charge of outreach efforts as they relate to dissemination of our data to conventional and organic growers using his Cooperative Extension network and experience. He attended data presentation meetings but was not involved in data dissemination since we only had one year of data. Eric Sideman, collaborator, Director of Technical Services/Crop Specialist of the Maine Organic Farmers and Gardeners Association (MOFGA) was the coordinator of the Grower Advisory Committee, and facilitated our presentations to organic growers at the 67th Augusta Trades Show. Edward Bernard, a Ph. D. candidate supported by the project, assisted in all field operations, conducted all soil microbiological analyses (fatty acids, BIOLOG, etc.), data analyses, and data presentation. Serena Gross, a M. S. graduate student, supported by the project, assisted in all field operations, was involved in insect sampling, assessing insect damage, analyses of the resulting data and other ad hoc tasks such as soil analysis. Jennifer Brown and Benjamin Richard, both undergraduate students, were hired to help with field operations and laboratory work (soil and microbial analyses). Peter Gerritsen, son of Wood Prairie Farm owner Jim Gerritsen, was employed part-time during the summer to help with field operations and sample collections. TARGET AUDIENCES: First-year data was presented as preliminary results at trade, professional and scientific meetings (see resentations above). PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
This was the first year of the study, and all findings are considered preliminary, and unsuitable for suggesting changes in knowledge or action.

Publications

• Bernard, E., Larkin, R.P., Tavantzis, S., Erich, S., Alyokhin, A., Gross, S. 2008. Compost and Biological Amendments in Potato Systems: Effects on Soil Microbial Communities. Northeast Potato Technology Forum, Fredericton, New Brunswick, Canada (Abstract).
• Tavantzis, S., Larkin, R.P., Alyokhin, A., Erich, S., Bernard, E., Gross, S. 2008. Compost and Biological Amendments in Potato Systems: Effects on Soilborne Diseases and Yield. Northeast Potato Technology Forum, Fredericton, New Brunswick, Canada (Abstract).
• Erich, S., Tavantzis, S., Larkin, R.P., Alyokhin, A., Gross, S. 2008. Compost effects on soil properties and fertility. 67th Annual Maine Agricultural Trades Show, Augusta, ME.
• Larkin, R.P., Alyokhin, A., Erich, S., Bernard, E., Gross, S.Tavantzis, S. 2008. Compost and biological amendment effects on soilborne diseases and yield in potato. . 67th Annual Maine Agricultural Trades Show, Augusta, ME.
• Erich, M. Susan, S. Tavantzis, R. Larkin, S. Gross and A. Alyokhin. 2008. Effect of Compost Amendment on Soil Properties in Low and High Organic Matter Soils. Joint Annual Meeting of GSA, SSSA, ASA, CSSA, GCAGS, HGS in Houston, TX. Joint Annual Meeting Program, p. 349.
• Larkin, R.P., Tavantzis, S., Bernard, E., Alyokhin, A., Erich, S., Gross, S. 2008. Compost and Biological Amendment Effects on Soilborne Disease and Soil Microbial Communities. Annual Meeting of the American Phytopathological Society. Phytopathology 98:586 (Abstract).
• Larkin, R. P., A. Alyokhin, M. S. Erich, E. Bernard, S. Gross, and S. Tavantzis. 2008. A Systems Approach for Enhancing Soil Functionality and Plant Health to Suppress Plant Diseases and Pests. IOP Project Directors Meeting and SARE Conference, Kansas City.
• Erich, S., Tavantzis, S., Larkin, R.P., Alyokhin, A., Gross, S. 2008. Compost and Biological Amendments in Potato Systems: Effects on Soil Properties and Fertility. Northeast Potato Technology Forum, Fredericton, New Brunswick, Canada (Abstract).
• Gross, S., A. Alyokhin, R. Larkin, S. Erich and S. Tavantzis. 2008. Reduced pest insect densities following compost application in organic and conventional systems. Northeast Potato Technology Forum, Fredericton, New Brunswick, Canada (Abstract).
• Alyokhin, A., Gross, S., R. Larkin, S. Erich and S. Tavantzis. 2008. Compost effects on insect pests of potato. 67th Annual Maine Agricultural Trades Show, Augusta, ME.