Final Report for LNC95-090

Project Type: Research and Education
Funds awarded in 1995: $80,000.00
Projected End Date: 12/31/1998
Matching Non-Federal Funds: $41,820.00
Region: North Central
State: Minnesota
Project Coordinator:
Nicholas Jordan
Dept of Agronomy and Plant Genetics, University of Minnesota
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Project Information

Summary:

[Please note: the Final Report for this project also covers the SARE Project ANC95-026, which has the same title.]

The overall objectives of our work were to: (1) determine the effectiveness of the bacterial biocontrol, Pseudomonas syringae pv. tagetis (PST) and competitive soybean varieties for control of Canada thistle in organic and no-till soybean production systems, and (2) to support development of new sustainable farming systems for the north-central region by initiating a broad-based cooperative research approach to develop integrated cultural and biological weed management.

Field studies were conducted in 1996 and 1997 to determine the effectiveness of the bacterial biocontrol, Pseudomonas syringae pv. tagetis (PST) and competitive soybean varieties for control of Canada thistle in both organic and no-till production systems. The competitive soybean variety “Kato” improved the efficacy of two cultivations for the control of Canada thistle and had numerically lower values with respect to height and seed production for Canada thistle when compared to the non-competitive variety “Evans” in organic soybean production. Kato reduced the total weed density and total weed dry shoot weight when compared to Evans in no-till soybean production but did not affect marked Canada thistles in no-till production. Soybean yield was independent of soybean variety.

PST reduced Canada thistle survival by 33%, 69%, 91%, and 93% in 1996 and by 11%, 32%, 68% and 70% in 1997 at 35, 51, 73 and 107 DAP respectively in organic soybean production. In no-till soybean production, PST reduced Canada thistle survival by 5% and 50% at 48 and 105 DAP in 1996 and by 16%, 28% and 60% at 48, 69 and 105 DAP in 1997 respectively. Canada thistle plants that survived treatment with PST were shorter and less likely to produce seed than untreated controls in both organic and no-till soybean production.

Differences in the efficacy of PST for control of Canada thistle in organic and no-till production could not be explained. PST had no impact on soybean yield. Two cultivations in organic soybean production did not improve soybean yield or weed control except in Kato where extra cultivation reduced both Canada thistle height and the average number of seed heads produced per plant.

The combination of Kato plus PST plus two cultivations always resulted in the lowest values for Canada thistle seed production and generally the greatest reductions in Canada thistle height suggesting that cumulative effects of multiple weed control measures in an integrated weed management program may successfully control this weed.

In no-till soybean production, the herbicide bentazon was more effective at reducing Canada thistle survival, height and seed production than PST but did not improve soybean yield suggesting that weed control measures in addition to post-emergent applications of imazethapyr and sethoxydim were not necessary to maintain soybean yield in this study.

Lack of yield differences between weed control treatments could not be explained. A Minnesota-based biocontrol company is cooperating with the University of Minnesota to develop the PST bacterium as a commercial weed control product.

In 1996-97 we worked to initiate a broad-based cooperative research approach to develop integrated cultural and biological weed management. An important outcome of our many discussions between farmers, researchers and extensionists is that we shifted the emphasis of our work from research to farmer learning.

We are currently establishing “learning communities” (LCs) composed of farmers, local extension educators, and research and extension weed scientists that will develop integrated cultural and biological weed management methods for soybean production. Each LC will work together to examine and adapt systems thinking tools, such as agroecosystem analysis, to devise an integrated weed management method. Each group will use the integrated weed management method experimentally, assess its practical value, help develop practical and convenient means for using the approach, and help refine it. A network of LCs could accelerate farmer learning about local challenges that arise in farming systems at farm, watershed and larger scales. Ultimately, LCs could have a significant and lasting impact on the way universities conduct agricultural research.

Introduction:

Weed management has focused on tillage and selective herbicides to reduce the impact of weeds on crop yields. While effective, chemical and mechanical control has led to excessive soil erosion, herbicide resistant weeds, and contamination of surface and groundwater. Integrated weed control methods including weed competitive crops and biological controls are now being investigated.

Field studies were conducted in 1996 and 1997 to determine the effectiveness of the bacterial biocontrol, Pseudomonas syringae pv. tagetis (PST) and competitive soybean cultivars, for control of Canada thistle. These experiments were conducted in organic and no-till production systems.

The competitive soybean variety “Kato” improved the efficacy of two cultivations for the control of Canada thistle and had numerically lower values with respect to height and seed production for Canada thistle when compared to the non-competitive variety “Evans” in organic soybean production. Kato reduced the total weed density and total weed dry shoot weight at 105 days after planting (DAP) by 43% and 55% respectively when compared to Evans in no-till soybean production but did not affect marked Canada thistles in no-till production. Soybean yield was independent of soybean variety.

PST reduced Canada thistle survival by 33%, 69%, 91%, and 93% in 1996 and by 11%, 32%, 68% and 70% in 1997 at 35, 51, 73 and 107 DAP respectively in organic soybean production. In no-till soybean production, PST reduced Canada thistle survival by 5% and 50% at 48 and 105 DAP in 1996 and by 16%, 28% and 60% at 48, 69 and 105 DAP in 1997 respectively. Canada thistle plants that survived treatment with PST were shorter and less likely to produce seed than untreated controls in both organic and no-till soybean production.

Differences in the efficacy of PST for the control of Canada thistle in organic and no-till production could not be explained. PST had no impact on soybean yield. Two cultivations in organic soybean production did not improve soybean yield or weed control except in Kato where extra cultivation reduced both Canada thistle height and the average number of seed heads produced per plant.

The combination of Kato plus PST plus two cultivations always resulted in the lowest values for Canada thistle seed production and generally the greatest reductions in Canada thistle height suggesting that cumulative effects of multiple weed control measures in an integrated weed management program may successfully control this weed.

In no-till soybean production, the herbicide bentazon was more effective at reducing Canada thistle survival, height and seed production than PST but did not improve soybean yield suggesting that weed control measures in addition to post-emergent applications of imazethapyr and sethoxydim were not necessary to maintain soybean yield in this study.

Lack of yield differences between weed control treatments could not be explained. The herbicide bentazon reduced total weed density and weed dry shoot weight by 68% and 84% respectively and Canada thistle survival was reduced 30%, 34%, 96% and 97% in 1996 and 24%, 52%, 88% and 95% in 1997 at 34, 48, 69, and 105 DAP respectively. These findings suggest that competitive soybean varieties and biological weed control are valuable components of an integrated weed management system.

We are establishing “learning communities” (LCs) composed of farmers, local extension educators, and research and extension weed scientists that will develop integrated cultural and biological weed management methods for soybean production. Each LC will work together to examine and adapt systems thinking tools, such as agroecosystem analysis, to devise an integrated weed management method.

Each group will use the integrated weed management method experimentally, assess its practical value, help develop practical and convenient means for using the approach, and help refine it. A network of LCs could accelerate farmer learning about local challenges that arise in farming systems at farm, watershed and larger scales. Ultimately, LCs could have a significant and lasting impact on the way universities conduct agricultural research.

Project Objectives:

1. Compare weed control of Canada thistle in an organic production system using competitive soybean varieties and bacterial biocontrol to current cultivation- and labor-intensive methods.

2. Compare weed control of Canada thistle in a no-till production system using competitive varieties, bacterial biocontrol, and reduced herbicide rates to current herbicide-intensive methods.

3. Collaborate with member organizations of the Sustainers’ Coalition of the Minnesota Institute for Sustainable Agriculture in presentations, discussions and evaluations of research findings at summer field days and winter workshops.

4. Initiate a broad-based cooperative research approach to develop integrated cultural and biological weed management, in order to reduce sediment and herbicide pollution associated with weed control, and support development of new sustainable farming systems for the north-central region.

Cooperators

Click linked name(s) to expand
  • Eric Hoeft
  • Dr. Gregg Johnson
  • Susan White
  • Dr. Donald Wyse

Research

Materials and methods:

Objective 1. Compare weed control of Canada thistle in an organic production system using competitive soybean varieties and bacterial biocontrol to current cultivation- and labor-intensive methods.

This experiment was conducted on a certified-organic farm in Madison, MN on a Buse-Barnes loam soil with pH 7.0 and 3% organic matter. Two soybean varieties and two cultivation treatments were used in combination with three weed control treatments. The soybean varieties used were “Kato” (a competitive variety) and “Evans” (a noncompetitive variety). The cultivation treatments were:

1. Two rotary hoeings and a single pass with a cultivator, 2-3 weeks after soybean emergence, to provide control of early-germinating weeds.

2. Two rotary hoeings followed by two cultivations. The first and second cultivations occurred at 2-3 and 4-5 weeks after soybean emergence, respectively. This intensive cultivation treatment represents a typical cultivation system used by organic soybean growers in Minnesota.

The three weed control treatments were:

1. Three spray applications of the biological control, Pseudomonas syringae pv. tagetis (PST), at 23, 28, and 35 days after planting.

2. Weed free: weeds were removed by hand every week for the first 6 weeks after soybean planting and every 2 weeks thereafter.

3. Weedy check: weeds received no PST application and remained in the plots throughout the growing season.

Thistle and soybean plants were tagged at the beginning of the growing season and their heights were measured at 23, 35, 51, 73 and 107 days after planting. Thistle seed head production was determined at the same time intervals as the heights. When the soybeans were physiologically mature, the following measurements were made: thistle and soybean biomass, soybean density, and overall weed density and mass. Soybean grain yields were determined at the end of the growing season.

Objective 2. Compare weed control of Canada thistle in a no-till production system using competitive varieties, bacterial biocontrol, and reduced herbicide rates to current herbicide-intensive methods.

This experiment was conducted at the University of Minnesota Experiment Station at Rosemount, MN, on a Waukegan silt loam, pH 6.6 and 4.5 % organic matter. There were no cultivation treatments since this was a no-till production system. The entire experimental area was treated with the herbicide glyphosate prior to planting the soybeans. Two weeks after planting, the herbicides imazethapyr and sethoxydim were applied to the entire experimental area. There were four weed control treatments in this study. Treatments 1, 2, and 3 were the same treatments used in the organic production system described above. Treatment 4 was an application of the herbicide bentazon applied 2 and 5 weeks after planting. Measurements taken during the growing season were the same measurements listed for objective 1.

Objective 3. Collaborate with member organizations of the Sustainers’Coalition of the Minnesota Institute for Sustainable Agriculture in presentations, discussions and evaluations of research findings at summer field days and winter workshops.

We are collaborating with one of the member organizations of the Sustainers’ Coalition of the Minnesota Institute for Sustainable Agriculture, the Sustainable Farming Association of Minnesota (SFA), to initiate the broad-based cooperative research approach described for objective 4. Many farmers from the SFA, along with the SFA statewide Research Committee, have been very active in this work. The Coordinator for the Sustainersƒ­ Coalition of the Minnesota Institute for Sustainable Agriculture (MISA) has also been involved in this work.

Objective 4. Initiate a broad-based cooperative research approach to develop integrated cultural and biological weed management, in order to reduce sediment and herbicide pollution associated with weed control, and support development of new sustainable farming systems for the north-central region.

To address this objective, we began to develop the general notion of a “research cooperative” in May of 1996. Our original concept of a research cooperative was farmer-researcher partnerships tied to conducting on-farm research. In the winter of 1996-97, researchers and extensionists were invited to dialogue with farmers from the SFA about collaborative development of usable knowledge to solve site-specific problems in sustainable farming. The outcome of these meetings was general agreement that site specific knowledge needed to preserve soil and water and diversify farming cannot be produced by farmers or scientists alone. Rather, farmers and scientists must work together to find sustainable ways of farming that fit in local situations.

The challenge is to find ways to pool farmer knowledge and scientist knowledge to create sustainable solutions. Our overall goal is to have broader public participation in construction of usable knowledge about agriculture and food systems. Our work is very much aligned with the mission of the SARE Program, i.e., “To create and manage a system designed to encourage the involvement of farm and non-farm citizens in the process of discovery and learning that leads to achieving a more sustainable, environmentally benign agriculture.” Our work to develop a broad-based cooperative research approach is described in the Results section of this report.

Research results and discussion:

Objective 1. Compare weed control of Canada thistle in an organic production system using competitive soybean varieties and bacterial biocontrol to current cultivation- and labor-intensive methods.

Field experiments were conducted in 1996 and 1997 to evaluate the efficacy of the bacterial biocontrol, PST, the competitive soybean variety “Kato” and two cultivations in an integrated weed management (IWM) system for the control of Canada thistle in organic soybean production. PST reduced Canada thistle survival by 33%, 69%, 91%, and 93% in 1996 and by 11%, 32%, 68%, and 70% in 1997 at 35, 51, 73 and 107 days after planting (DAP) respectively. Average height of surviving Canada thistle shoots was an average of 63% less in 1996 and 57% less in 1997 in plots treated with PST. PST reduced seedhead production on surviving Canada thistle plants by an average of 100% in 1996 and 85% in 1997. Kato had no significant impact on Canada thistle survival, height or seed production when compared to the non-competitive soybean variety “Evans” for both years. Two cultivations in Kato reduced Canada thistle height by 42% at 35 and 42% at 51 DAP in 1996 for plants not treated with PST. Two cultivations did not reduce Canada thistle height in 1997 for either variety. Two cultivations had no impact on the number of Canada thistle plants producing seed in each plot in both years but caused a 38% and 83% reduction in the total number of seed heads produced per plant at 51 and 73 DAP respectively in 1996. Soybean yield did not differ between plots treated or untreated with PST, which suggests the biocontrol agent is suited to soybean production. Soybean yield did not differ between plots receiving one or two cultivations. Yield did not differ among soybean varieties in 1997, however Evans yielded 9% more than Kato in 1996. There were no significant interactions between PST, soybean variety or cultivation for Canada thistle survival, suggesting that the combined weed control effects of each measure were additive. However, the combination of Kato plus PST plus two cultivations consistently resulted in the lowest values for seed production.

Objective 2. Compare weed control of Canada thistle in a no-till production system using competitive varieties, bacterial biocontrol, and reduced herbicide rates to current herbicide-intensive methods.

Field experiments were conducted in 1996 and 1997 to evaluate the efficacy of the biocontrol agent PST and the herbicide bentazon in soybean varieties “Kato” and “Evans” for an integrated weed management system to control Canada thistle and other weeds in a no-till soybean production system. PST reduced Canada thistle shoot survival by 5% and 50% at 48 and 105 DAP respectively in 1996 and by 16%, 28% and 60% at 48, 69 and 105 DAP respectively in 1997 compared with controls. Height of Canada thistle shoots that survived treatment with PST was 29% less in 1996 and 36% less in 1997 than untreated plants when averaged over sampling dates. PST reduced seedhead production on surviving Canada thistle plants by an average of 71% in 1996 and 86% in 1997. Bentazon provided the best control of Canada thistle and reduced survival by 30%, 34%, 96% and 97% in 1996 and by 24%, 52%, 88% and 95% in 1997 at 34, 48, 69 and 105 DAP respectively. Height of Canada thistle plants that survived bentazon treatment was always less than controls and bentazon reduced seed production by an average of 70-100%. Height differences in surviving Canada thistles between bentazon and PST treatments were not observed until 69 DAP in both years. Soybean variety was not a significant predictor of Canada thistle survival but Evans reduced Canada thistle height by 15% at 48 DAP in 1996 for weedy control plots when compared to Kato and while not statistically significant, was less for Evans in most treatments in both years. In Evans, surviving Canada thistles produced 43% and 48% fewer seed heads per plant at 48 and 69 DAP respectively in 1996 and 75% fewer seed heads per plant at 105 DAP in 1997 when compared to Kato. Bentazon reduced total weed density and dry shoot weight at 105 DAP by 68% and 84% respectively. Kato reduced total weed density and dry shoot weight at 105 DAP by 43% and 55% respectively when compared to Evans. Kato also enhanced the efficacy of PST by improving reductions in total weed densities and dry shoot weights observed in PST treated plots by 48% and 57% respectively at 105 DAP when compared to Evans. Soybean yield did not differ among treatments or soybean varieties. Combined effects of the competitive soybean variety Kato and other weed control treatments were observed in the general weed population at 105 DAP and provided better control than each treatment alone. Our findings are consistent with the hypothesis that careful combination of weed control measures in an integrated weed management system can improve weed control in no-till soybean production.

Objective 3. Collaborate with member organizations of the Sustainers’ Coalition of the Minnesota Institute for Sustainable Agriculture in presentations, discussions and evaluations of research findings at summer field days and winter workshops.

There has been extensive collaboration with farmers from the SFA and the Coordinator of MISA as described in the Methods/Approach and Results sections for objective 4.

Objective 4. Initiate a broad-based cooperative research approach to develop integrated cultural and biological weed management, in order to reduce sediment and herbicide pollution associated with weed control, and support development of new sustainable farming systems for the north-central region.

After several group discussions during the winter of 1996-97, there was agreement between farmers and researchers that we have struggled to develop knowledge collaboratively. Many of the farmers involved in these conversations have seen, first-hand, both the potential and challenges of group learning about complex farming systems. Farmers, researchers and extensionists all agreed there is an urgent need to develop an operational model for such collaborative learning.

As an outcome of many one-on-one conversations with diverse stakeholders to explore their perceptions and interests, we organized a diverse planning team in May 1997 to plan “learning communities” (LCs) composed of farmers and other agriculturalists, for local inquiry in sustainable agriculture. The planning team is composed of farmers, researchers, and the Coordinator of the Minnesota Institute for Sustainable Agriculture. As we have progressed in our work, we believe that a “research cooperative” approach should be more focused on systems-level work oriented toward supporting transition to more biologically-rich and diversified agroecosystems. Moreover, we have shifted the emphasis of our work from research to farmer learning. This shift has been motivated by agreement in our planning group that farmer-participatory research has often been driven by the agendas of academic scientists. Our extensive organizing and planning work have led us to our current perspective. In what follows, we describe our plan of work to develop the LCs. This work plan is presented in the Results section because it is the result of many in-depth conversations of the planning team interacting with regional SFA chapters.

In our work to develop LCs , we will integrate several existing methods for planning and managing multidimensional farm operations. Agroecosystem analysis is a method for systematically learning about interactions between parts of a farm operation. Its premise is that these interactions determine much about the operation, including outcome of pest management efforts. Producers are typically well aware of many important interactions, but a number of others are not considered. AEA helps producers capture, organize and make more effective use of their knowledge of the components of a farm operation. We will link AEA to an adaptive management approach based on use of the inquiry cycle , a systematic method for inquiry into pest management problems by farmers. We believe that this approach will allow producers to align time and labor management with site-specific factors significantly more effectively than is possible with existing methods.

In our application, the key feature of AEA is a process of “pattern analysis,” in which the major parts of a farm operation relevant to weed management are mapped and diagramed to organize existing information, reveal key uncertainties, and identify important interactions (e.g., between fertilizing, weed control and tillage operations). Information used in pattern analysis can come from observations, experience, published sources, “precision-farming” tools such as yield monitors, etc. To implement AEA to guide diversified weed management, relevant parts of the operation are identified, and then pattern analysis is carried out. Pertinent issues for pattern analysis will include patterns in time, space, flow and decision making.

Pattern analysis can be used by the producer to select among and integrate with the farm operation a variety of non-chemical weed control methods that may be available. These include: crop rotation, crop variety selection and seeding rate, cover crops, planting timing, soil moisture management, tillage and residue management, mechanical control, fertility management, reduced herbicide rates and others. The outcome of our approach is improved understanding of how an ongoing weed infestation is sustained in a given operation, of the range of applicable non-chemical control options, and of potential conflicts and synergies between these options and other important farm operations. Initial pattern analyses will be crude, but pattern analysis is an ongoing process that will lead to successive refinement of weed management and related farm operations.

Over the next two years we plan to establish two or more learning communities that will work to develop an integrated weed management approach through the method described above. Each LC will use the integrated weed management approach experimentally, assess its practical value, help develop practical and convenient means for using the approach, and help refine it.

Research conclusions:

The potential contribution of PST for weed control in soybeans is that it may be able to provide a reliable nonchemical weed control for Canada thistle, which is a noxious weed. If PST was commercially available, it is likely that it would be approved for certified organic soybean production. PST may become a profitable product for “Encore,” a Minnesota-based bio-control company that is cooperating with the University of Minnesota to develop the PST bacterium as a commercial weed-control product.

There are several potential contributions from a network of farmer LCs. A network of LCs would accelerate farmer learning about local challenges that arise in sustainable farming systems, at farm, watershed and larger scales, and could promote translation for such learning into policy-making for sustainability. Ultimately, farmer LCs could have a significant and lasting impact on the way universities conduct agricultural research.

Farmer Adoption

One of our cooperators, Carmen Fernholz, has played an active role in the PST research on his farm, but it is too early to estimate the number of farmers reached through this project. We have no specific recommendations for use of PST in soybean production at this time, since it is still not commercially available. However, work is underway to develop PST as a commercially available weed control product as described in section 6 above. Many farmers have been directly involved in the planning and development of the experimental learning communities. There is great potential for large numbers of farmers to be directly involved in learning communities.

Testimonials

Carmen Fernholz reports: “According to my visual observations several times this summer, and based on the analyzed data, the Pseudomonas appears to perform nearly perfect. Because it appears to be rather effective, we are planning to expand this research in several ways in 1998 if we can get funding and coordination to put it together.” As of June 1998, this research is underway at the Fernholz farm.

Involvement of Other Audiences

We have involved both farmers and non-agriculturalists in our work to develop LCs. Our administrators have been enthusiastic and supportive of this work. We are linking our work with the work of Extension Educators from University of Minnesota Extension Service. Over the past year, our project has become affiliated with the Visions for Change Project, a Kellogg Foundation-funded project for institutional change within land-grant universities.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:

Results from the 1996 field experiment from the organic production system were presented by Eric Hoeft in a poster presentation on December 11, 1996 at the North Central Weed Science Society of America meetings in St. Louis, MO. In June 1997, Carmen Fernholz hosted a field day on his farm and shared the results of the PST study with about 70 farmers. In the summer and fall of 1997, Nicholas Jordan and Susan White made several presentations about the work plan to develop experimental LCs. Presentations were given to the State Board of the Sustainable Farming Association of Minnesota, two of the regional SFA chapters, and to the semiannual Minnesota Active Citizenship “Institutes” that are held as a part of a large statewide effort called the Minnesota Active Citizenship Initiative. This initiative is a long term effort to develop civic leadership as a new base for democratic governance in a wide variety of areas, including agriculture and natural resources, University of Minnesota Extension Service, businesses, churches, education, and others.

In August 1997 we were awarded a small planning grant to help plan the LCs from the Visions for Change Project, part of a national Food Systems Professions Education (FSPE) program funded by the W.K. Kellogg Foundation that seeks to engage the public in strengthening the food system. Our work to plan and develop farmer learning communities will be publicized through many channels of the Kellogg Foundation.

An article about our work to develop LCs was published in 1997:

Susan K. White and Nicholas R. Jordan. July 1997. Active Citizenship and Developing Farmer-Researcher Learning Communities. Consortium News (Consortium for Sustainable Agriculture Research and Education). 15:5.

Project Outcomes

Recommendations:

Areas needing additional study

Although PST has provided effective control of Canada thistle in an organic production system over the past two years, additional years of field research are needed to confirm the efficacy of PST as a reliable, nonchemical weed control method for Canada thistle in organic soybean production systems. Based on two years of field studies, it appears that PST may be more suitable for organic production systems than for no-till systems. Additional time is required to develop PST as a commercially available weed control product.

Additional time and funding are needed to develop a network of farmer learning communities. In the spring of 1998 we were awarded grants from the Minnesota Soybean Research and Promotion Council and the USDA North Central Region Integrated Pest Management Program to develop management methods, through learning communities, that will aid the adoption of integrated weed management in soybean and other crop production systems.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.