Transition Strategies that Control Perennial Weeds and Build Soil

TRANSITION STRATEGIES THAT CONTROL PERENNIAL WEEDS AND BUILD SOIL

Sponsoring Institution

National Institute of Food and Agriculture

Project Status

COMPLETE

Funding Source

OTHER GRANTS

Reporting Frequency

Annual

Accession No.

0207346

Grant No.

2006-51300-03544

Cumulative Award Amt.

(N/A)

Proposal No.

2006-02014

Multistate No.

(N/A)

Project Start Date

Jul 1, 2006

Project End Date

Jun 30, 2011

Grant Year

2006

Program Code

[113]- Integrated Organic Program

Recipient Organization
OHIO STATE UNIVERSITY
1680 MADISON AVENUE
WOOSTER,OH 44691

Performing Department
HORTICULTURE AND CROP SCIENCE

Non Technical Summary
Perennial weeds are one of the most important problems for adoption, expansion, and sustainability of organic farming. Perennials are a challenge because they produce long-lived underground structures that survive cultivation other control tactics. A survey of organic growers in Ohio showed that perennial weed control was the major limitation to successful transition; some growers were ready to abandon organic methods because of problems with perennial weeds. Perennial weeds require years of persistent effort for effective control, especially in vegetable crops that are not competitive against weeds. Current control methods disturb the soil so much that soil-building goals of organic management are ineffective. Organic farmers need to know how to design transition strategies that allow them to control perennial weeds while building the soil and gaining a financial return during and after transition. We will develop and evaluate transition strategies and outreach information for management of perennial weeds while enhancing soil quality for organic vegetable crop production. Biologically-based and properly timed control efforts, integrated with soil building measures, will provide effective and economical transition strategies that can be readily adopted by organic and transitioning farmers. The research is a response to feedback we have received from organic farmers during our on-farm weed survey as well as during workshops and presentations and telephone conferences.

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0110	1060	20%
205	2410	1010	20%
213	2300	1070	40%
601	6230	3010	20%

Knowledge Area
601 - Economics of Agricultural Production and Farm Management; 102 - Soil, Plant, Water, Nutrient Relationships; 205 - Plant Management Systems; 213 - Weeds Affecting Plants;

Subject Of Investigation
0110 - Soil; 6230 - Marketing systems and sectors thereof; 2410 - Cross-commodity research--multiple crops; 2300 - Weeds;

Field Of Science
1060 - Biology (whole systems); 1070 - Ecology; 1010 - Nutrition and metabolism; 3010 - Economics;

Keywords

Goals / Objectives
1) Evaluate the biological and economic impacts of strategies for transitioning to organic vegetable production in fields with perennial weeds. 2) Evaluate the impact of on-farm management strategies on perennial weeds and soil quality. 3) Facilitate development of a learning community to share, evaluate, and generate information on problems with perennial weeds during transition.

Project Methods
There will be four basic cropping systems: clean fallow + smother crops, a standard one-crop/year with cultivation, a fabric-culture system designed by a local organic grower, and short-season crops that allow frequent cultivation. Within each system will be three nutrient management options: an untreated control, annual compost applications, and annual compost plus high-calcium lime and other OMRI-approved nutrient additions to achieve nutrient ratios recommended by biodynamic farmers. These treatments will be imposed in an alfalfa/grass hay field, which represents a typical starting point for transition to organic vegetables. This will allow us to evaluate a wide range of strategies that incorporate different mechanical, cultural, and natural-product weed management options together with different nutrient management levels. Performance of these strategies will be evaluated using biological indicators (soil quality, weed suppression) and economic returns during transition, and during the first vegetable crop season after transition. The combination of weed management with nutrient management options will allow us to explore weed/soil interactions that are of great interest to organic farmers. We will work with cooperating farmers to study how perennial weed patches respond to grower management practices. Our rationale is that understanding the behavior of perennial weed populations in response to variations in farm field conditions, soil quality indicators, and farmer management decisions will help us design farm-relevant transition strategies that are more effective in perennial weed suppression. We will focus on the most important perennial weeds identified by farmer cooperators; these are Canada thistle, quackgrass, yellow nutsedge, and field bindweed. In fields that have been managed as pasture or reduced-tillage corn/soybean rotations, it is fairly easy to discern discrete patches of these perennials, due to their interconnected underground vegetative connections. These species also occur in patchy distributions along field edges, from which they spread into otherwise well managed crop fields. Farmers will choose fields that have known perennial weed infestations and patches will be selected to monitor and map changes in these patches and in soil quality indicators; data will also be collected on all inputs and management operations in the fields of interest. Outreach activities will be developed through informal learning communities that have self-organized among organic farmers in Ohio. We will integrate relevant foundational biology and ecology into this network and to bring to it increased scientific rigor to evaluate results from participatory experiments that will be conducted under the domain of this proposal.

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

Outputs
OUTPUTS: Studies were conducted to evaluate the effects of five organic transition strategies on soil quality, weed suppression, and yield of tomato and potato in the first year of organic production. The transition strategies included a tilled fallow, non-treated weedy, high diversity prairie mixture, smother crops, and vegetable rotation. Subplots with and without compost application were also included. Another study was conducted to determine optimal tef and sorghum-sudangrass mixtures for biomass production and weed suppression. Tef and sorghum-sudangrass were planted in monoculture and in mixture with soybean and sunflower. The percentage cover of crops and weeds and height of crops were measured weekly, and final biomass was measured for component crops and weeds. Biomass was used to calculate the land equivalent ratio (LER) and aggressivity indices of crops in mixture. Another study was conducted to evaluate tef as a smother crop for management of weeds during transition to organic production. Greenhouse and field trials were conducted to evaluate the growth of eight tef varieties and their effect on Canada thistle and annual weeds. A major cropping system study was conducted to evaluate smother crop mixtures seeded, at different times, for Canada thistle control. Field trials were established to evaluate the ability of smother crop mixtures to suppress Canada thistle growth and development. Results were shared with organic farming audiences at annual field days and at the Ohio Ecological Food and Farming Association annual meeting. Presentations were made and posters displayed at regional and national scientific meetings. In-field presentations were made at urban garden sites to adult and youth groups. One doctoral graduate student completed a dissertation based on this work, and three peer-reviewed publications about this work are in print. Annual field days were held for the public to tour our field plots and learn about the organic research. Workshops were presented at an upscale organic foods market (two locations) to provide practical information to the consumer, gardener, and farmer about organic food production, food safety and to bridge the gap between local organic food producers and consumers. Investigators on this project conducted lectures in an undergraduate course, Organic Farming and Gardening offered at the Agricultural Technical Institute for associate degree students. PARTICIPANTS: Stephanie Wedryk, Catherine Herms, Peter McDonough, Joel Felix, Douglas Doohan, Ohio Ecological Food and Farming Association, Ohio State University Agricultural Technical Institute, Ohio Agricultural Research and Development Center Organic Food and Farming Education and Research program. TARGET AUDIENCES: Organic farmers, transitioning farmers, extension educators, and researchers are the main audience for this project. Efforts to change knowledge in this audience included annual field days and presentations at various meetings. Presentations were made and posters displayed at regional and national scientific meetings. In-field presentations were made at urban garden sites to adult and youth groups. Annual field days were held for the public to tour the field plots and share results. Workshops were presented at grocery stores, and lectures were presented in an undergraduate course. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Transition strategies affected weed density and biomass in the first organic year with the prairie strategy being the most suppressive. Compost application increased plant available nutrients and soil organic matter. The fallow transition strategy improved the quantity of plant available P and K 33 and 15 percent, respectively, while the prairie strategy improved soil organic matter by 10 percent or more. Compost application increased yields of potato 50 percent and tomato 17 percent, with transition strategy affecting the number and weight of cull potato tubers. Canonical correlation analysis showed that plant available nutrients strongly influenced potato yield while organic matter affected tomato yield. Biomass production was affected by the species of grass in monoculture or mixture, but land-equivalent-ration was greater in 3-species mixtures than monoculture. Aggressivity of grass crops was linearly related to total land-equivalent-ratio in 2- and 3-species mixtures. Percent cover of crops was greater in multi-species mixtures and weed cover was suppressed 70 and 45 percent in 2008 and 2009 by multi-species mixtures. The biomass and percent cover of the grass crop in mixture or monoculture was related to total biomass production and percent cover. Canada thistle biomass was suppressed 50 percent in 2009 and 87 percent in 2010 by the sorghum-sudangrass mixture. The oat mixture suppressed annual weed biomass more than 58 percent. Canada thistle shoot density and percent cover were affected by the crop mixture in 2009 and 2010, with sorghum-sudangrass being the most suppressive. Tef decreased the biomass of Canada thistle shoots and rhizomes 44 to 74 percent depending on variety. In field studies, tef varieties suppressed annual weeds 35 to 54 percent, but there were no differences among varieties. Canada thistle growth was suppressed 73 percent by tef in 2008 and 37 percent in 2009, a year of cooler temperatures and unseasonal rainfall. All tef varieties except Pharaoh were competitive with Canada thistle in the field experiment. The transition strategy implemented during the 3 years prior to organic farming can affect the weed density and biomass in the first year of organic production. The use of native, perennial prairie species can suppress Canada thistle, monocot, and broadleaf weeds. Prairie species are also a potential source of biofuel feedstocks for ligno-cellulosic fuel markets that may provide economic return during transition. Smother crops were effective at reducing populations of Canada thistle and weed biomass. Compost applications and transition strategies during organic transition improved soil fertility and quality. During the first year of organic production, compost application strongly affected potato and tomato yield and quality. In potato production, plant available nutrients had the strongest influence on yield. Transition strategies that increase soil nutrients were most effective in improving yields in the first year of organic potato production. However, in tomato production, improving OM in the soil may have the strongest influence on first-year organic yields.

Publications

Wedryk, S., J. Felix, D. Doohan, and J. Cardina. 2012. Strategies for weed suppression and improving soil fertility during transition to organic vegetable production. Hort Technology 22:207-214.
Wedryk, S. and J. Cardina. 2012. Smother crop mixtures for Canada thistle suppression in organic transition. Weed Science. In Press.
Wedryk, S. and J. Cardina. 2012. Evaluation of tef as a smother crop during transition to organic management. Weed Technology 26:102-109.

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

Outputs
OUTPUTS: Soil samples were taken to study the impact of transition strategies and compost addition on soil quality. Transition strategies implemented were: Nontreated - allow weeds to grow and mow once per year; Fallow - disk field when weeds grow to be 5-6 cm; Biomass - a mix of sixteen native prairie species was planted in year one; Vegetable -four varieties of edamame soybeans were planted in year one, mixed vegetables (lettuce, cabbage, kale, brussel sprouts) in year two; and edamame soybeans in year three; Smother crop -a commercial blend of Royal oats and Packer peas was planted in year one; a mix of soybean and sorghum-sudangrass in subsequent years. The crop mixes provided a dense cover of the plots to control Canada thistle and annual weed growth by preventing light from reaching the soil surface. Additional smother crop studies included work on the interaction of three planting dates and three smother crop mixes on Canada thistle and other weed control. The three mixes are: Royal oats, Packer peas, and Florida Broadleaf India mustard; VA-T1 tef, Santiago burr medic, and buckwheat; Special Effort sorghum-sudangrass, Stonewall forage soybeans, and S678 sunflower. Additional work compares the smothering ability of eight tef varieties as well as a comparison between sorghum-sudangrass smother crop mixes and tef crop mixes. Combinations of grass, legume, and forb species were used as smother crop mixes, but crimson clover and kenaf did not perform well against Canada thistle. Different planting times of smother crop mixes were tested for smothering ability against Canada thistle. We evaluated mixtures of smother cropping species for suppression of Canada thistle in field and greenhouse experiments. Eight varieties of Tef were evaluated as a smother crop against early emerging Canada thistle. We hosted The Organic Food and Farming Education and Research (OFFER) Field Day as part of their annual tour, along with visitors from around Ohio and neighboring sttes. PARTICIPANTS: J. Cardina D. Doohan C. P. Herms S. Walker D. Stinner Z. Hussain E. Duarte TARGET AUDIENCES: Organic Food and Farming Extension and Research (OFFER) Ohio Ecological Food and Farming Association PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
The crimson clover did not grow tall enough to be competitive. Other mixes that included any combination of sorghum-sudangrass, tef, soybean, and sunflower were competitive against Canada thistle and effectively smothered it. Canada thistle affected by these mixes had weak stems and fewer and weaker thistles. The most competitive mix was sorghum-sudangrass, soybean, and sunflower. In the next year, only sorghum-sudangrass, soybean, tef, and sunflower will be tested in smother crop mixes. Of the mixes planted on May 1, the oat, pea, mustard mix smothered Canada thistle most effectively. The second planting date was May 22 and the mix seeded on this date that suppressed Canada thistle most effectively was sorghum-sudangrass, soybean, and sunflower. Of the mixes planted on June 15, the tef, burr medic, and buckwheat mix was the most competitive against Canada thistle. The variety Pharaoh was most effective in weed suppression. The differences in smothering ability of tef varieties will be further explored in the next year. Germination and competitiveness of seedlings against Canada thistle will be investigated to see if differences at these stages help to confer a competitive advantage of varieties. Smother crops suppressed some of the worst weeds of vegetable production while building soil carbon and providing economic return during the transition from conventional to organic production. Perennial weeds, such as Canada thistle, are most difficult to control since certification measures require that no herbicides be used for three years prior to harvest of the first organic crop. Establishment of the smother crops was difficult, and in a cool growing season, thistle can out-grew smother crops that are adapted to warmer conditions.

Publications

No publications reported this period

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

Outputs
OUTPUTS: Five management strategies for transitioning from conventional to organic vegetable production were evaluated for weed suppression and soil quality. This was the final year of the transition period, to be followed by a year with a uniform crop in all plots. The biomass crop consisted of a diverse mix of prairie species, which was dominated by Rudbekia triloba. The vegetable treatment plots were planted to two varieties of edamame soybeans, both of which emerged poorly and did not compete effectively with weeds. A clean fallow was difficult to achieve, due to heavy infestation with Canada thistle, which was often more dense than in the non-treated control plots. Combinations of grass, legume, and forb species were used as smother crop mixes. Two species, crimson clover and kenaf did not perform well against Canada thistle. The crimson clover did not grow tall enough to be competitive. Other mixes that included any combination of sorghum-sudangrass, tef, soybean, and sunflower were competitive against Canada thistle and effectively smothered it. Canada thistle affected by these mixes had weak stems and fewer and weaker thistles. The most competitive mix was sorghum-sudangrass, soybean, and sunflower. In the next year, only sorghum-sudangrass, soybean, tef, and sunflower will be tested in smother crop mixes. Different planting times of smother crop mixes were tested for smothering ability against Canada thistle. Of the mixes planted on May 1, the oat, pea, mustard mix smothered Canada thistle most effectively. The second planting date was May 22 and the mix seeded on this date that suppressed Canada thistle most effectively was sorghum-sudangrass, soybean, and sunflower. Of the mixes planted on June 15, the tef, burr medic, and buckwheat mix was the most competitive against Canada thistle. The experiment will be repeated in the next growing season.We evaluated mixtures of smother cropping species for suppression of Canada thistle in field and greenhouse experiments. Eight varieties of Tef were evaluated as a smother crop against early emerging Canada thistle. The variety "Pharaoh" was most effective in weed suppression. The differences in smothering ability of tef varieties will be further explored in the next year. Germination and competitiveness of seedlings against Canada thistle will be investigated to see if differences at these stages help to confer a competitive advantage of varieties. PARTICIPANTS: Individuals who worked on the project: Stephanie Wedryk, graduate research associate, Lourdes Arreuta, visiting scholar, Eileen Duarte, visiting scholar Zahid Hussain, visiting scholar. Partner organizations include the following: Organic Food and Farming Education and Research (OFFER), interdisciplinary team Ohio Ecological Food and Farming Association (OEFFA) TARGET AUDIENCES: The target audience is farmers transitioning from conventional to organic production. This might be an entire farm, or in most cases, one field at a time on an existing organic farm. To help facilitate this, we have participated in two courses called "Organic 101" and "Organic 201" which were presented in two locations to new and transitioning farmers. The data we collect from this project are summarized and put into a form for presentation to this audience. Our eventual goal is to contribute to a book on transition of agricultural systems. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
OARDC research is pointing to smother crops like sorghum, tef, and forage-type soybeans to help farmers suppress tough weeds like Canada thistle during the three-year transition period from conventional to organic crops. Also effective are diverse mixes of native prairie plants that could be harvested as a biofuel crop. Results show that these smother crops can suppress some of the worst weeds of vegetable production while building soil carbon and providing economic return during the transition from conventional to organic production. Worst are perennial weeds, like Canada thistle, since certification measures require that no herbicides be used for three years prior to harvest of the first organic crop. However, researchers caution that establishment of the smother crops can be difficult, and in a cool growing season, such as early 2009, thistle can out-grow smother crops that are adapted to warmer conditions. Combinations of early season tillage followed by vigorous crops like sorghum-sudangrass can keep Canada thistle from spreading and deplete the energy reserves in the thistle rhizomes.

Publications

No publications reported this period

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

Outputs
OUTPUTS: Different smother cropping strategies were tested against Canada thistle. Tef was tested as a smother crop and effectively outcompeted Canada thistle. Eight different varieties were tested and "Pharaoh" variety showed the best ability to smother Canada thistle. The differences in smothering ability of tef varieties will be further explored in the next year. Germination and competitiveness of seedlings against Canada thistle will be investigated to see if differences at these stages help to confer a competitive advantage of varieties. Combinations of grass, legume, and forb species were used as smother crop mixes. Two species, crimson clover and kenaf did not perform well against Canada thistle. The crimson clover did not grow tall enough to be competitive. Japanese beetles damaged the kenaf shortly after planting. Other mixes that included any combination of sorghum-sudangrass, tef, soybean, and sunflower were competitive against Canada thistle and effectively smothered it. Canada thistle affected by these mixes had weak stems and fewer and weaker thistles. The most competitive mix was sorghum-sudangrass, soybean, and sunflower. In the next year, only sorghum-sudangrass, soybean, tef, and sunflower will be tested in smother crop mixes. Different planting times of smother crop mixes were tested for smothering ability against Canada thistle. Of the mixes planted on May 1, the oat, pea, mustard mix smothered Canada thistle most effectively. The second planting date was May 22 and the mix seeded on this date that suppressed Canada thistle most effectively was sorghum-sudangrass, soybean, and sunflower. Of the mixes planted on June 15, the tef, burr medic, and buckwheat mix was the most competitive against Canada thistle. The experiment will be repeated in the next growing season. PARTICIPANTS: Individuals who worked on the project: Stephanie Wedryk, graduate student Eileen Duarte, visiting scholar Zahid Hussain, visiting scholar Partner organizations include the following: Organic Food and Farming Education and Research (OFFER), interdisciplinary team Ohio Ecological Food and Farming Association (OEFFA) TARGET AUDIENCES: The target audience is farmers transitioning from conventional to organic production. This might be an entire farm, or in most cases, one field at a time on an existing organic farm. To help facilitate this, we have participated in a course called "Organic 101" which was presented in two locations in 2008 to new and transitioning farmers. The data we collect from this project is summarized and put into a form for presentation to this audience. Our eventual goal is to contribute to a book on transition of agricultural systems. PROJECT MODIFICATIONS: No major changes.

Impacts
OARDC researchers are finding ways to transition from conventional to organic vegetable production in the worst of circumstances: a field infested with Canada thistle. Troublesome perennial weeds, like Canada thistle, are one of the main impediments to the adoption of organic farming, since certification measures require that no herbicides be used for three years prior to harvest of the first organic crop. OARDC scientists are finding that smother crops like sorghum, tef, and forage-type soybeans can help farmers suppress thistle during the three-year transition period. Also effective are diverse mixes of native prairie plants that can be harvested as a biofuel crop. Research at OARDC is providing farmers with novel management strategies that suppress the worst weeds of vegetable production while building soil carbon and providing economic return during the transition from conventional to organic production.

Publications

No publications reported this period