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Graduate Student Organic Agriculture Research Projects

Currently, 17 graduate students are conducting M.S. or Ph.D. thesis research in organic agriculture at Washington State University. Student projects include organic wheat breeding, cover crops as organic nutrient sources, compost development and use, biological control in organic orchards, quality of organic strawberry production systems, organic orchard productivity, weed management in organic systems, soil quality in organic systems, and organic seed treatments. Several of these students are supported by the CSANR Organic Cropping Research Grant.

Agricultural Systems

WSU-On-Farm Mortality Composting Research and Education Project

Name of student

Caitlin Price

Degree

MS

Department

Crop and Soil Sciences

Advisors

Lynne Carpenter-Boggs

Other committee members

Rich Koenig (CSS), Donald Nelson (Animal Sciences), Jessica Goldberger (Community and Rural Sociology)

Start year

2006

Year of completion

2008

Abstract

The WSU On-Farm Mortality Composting Research and Education Project is an inter-disciplinary extension focused project that is jointly funded by the WSU BIOAg program, Washington State Department of Ecology, and Washington State Department of Agriculture. With the proper management and materials, on-farm composting can be an economically viable and environmentally sound method of routine or catastrophic mortality disposal. Composting provides producers a much needed alternative to current disposal options. The first phase of this project consisted of a series of field trials with dairy and beef producers across Washington state to promote on-farm mortality composting and evaluate different methods and available materials, development of an informational website and printed materials, and evaluation of the new WA DOE guidelines. The second phase of this project will include more field trials, publication of an extension bulletin, and focused outreach to producers and regulators around the state.

Publications

Developing crop-livestock farming systems for organic grain production in Washington State

Name of student

Stephen Bramwell

Degree

MS

Department

Department of Crop and Soil Sciences

Advisors

Lynne Carpenter-Boggs

Start year

2006

Year of completion

2008

Abstract

Organic grain production in the Palouse is inhibited in many cases by lack of weed control and inadequate fertility. Soil building cover crops have been unsuccessful because the financial costs of not growing grains are too high to justify the time out of production. We are looking at the potential of grazing livestock on cover crops to provide income during the soil building phase, and to control weeds and assist nutrient cycling at the same time. Our research focuses on management questions, including how to mechanically eradicate tenacious stands of perennial cover crops, grain yield following the perennial phase, timing and amount of nitrogen available to these grain crops, and a host of questions dealing with pasture establishment, pasture productivity, livestock performance and infrastructure costs. Data collected will help assess the economic and energetic performance of integrated crop-livestock farming systems in the Palouse.

Publications

Influence of Various Environmental Factors on the Nitrate Content of Winter Grown Leafy Greens

Name of student

Kristy Ott

Degree

MS

Department

Department of Crop and Soil Sciences

Advisors

Rich Koenig, Carol Miles and John Reganold

Start year

2005

Year of completion

2007

Abstract

With proper planning and variety selection, vegetables such as lettuce, spinach and Asian greens can be viable winter crops in Washington State. However, many environmental factors can cause winter-grown leafy greens to accumulate high amounts of nitrates that could potentially cause methemoglobinemia in infants and cancer in adults. In regards to this crop, the purpose of this study is to examine: 1) the effects of variety, location, and time of harvest on nitrate concentration; 2) the effects of different organic nitrogen sources on the nitrate content; 3) the effect of storage conditions on nitrate content; and 4) the differences in the distribution and location of nitrate throughout the plant. This study is being conducted in an unheated and unlit organic field hoophouse in Pullman/Moscow and in Vancouver, Washington. Anticipated outcomes include finding cultural strategies that reduce nitrate content in winter-grown leafy vegetables while providing Washington growers with an affordable opportunity to produce winter vegetables.

Publications

Orchard Productivity and Apple Fruit Quality of Organic, Conventional, and Integrated Farm Management Systems

Name of student

Greg Peck

Degree

MS

Department

Department of Horticulture and Landscape Architecture

Advisor

Preston Andrews and John Reganold

Start year

2001

Year of completion

2004

Abstract

The study includes the ninth and tenth years of a side-by-side replicated trial comparing apple orchard systems in the Yakima Valley of Washington state.

Publications

Paper on student’s thesis research project has been accepted for publication in HortScience pending revision.

Marketing and Economics

Assessment of Organic Apple Production in Washington State

Name of student

Joe Sherburn

Degree

MA

Department

Agricultural Economics and Rural Sociology, Univ. of Idaho

Advisor

Holly Hong Wang

Start year

2003

Year of completion

2005

Abstract

Publications

Income Risk Assessment of Organic Apple Production in the Pacific Northwest

Name of student

Xiaomei Chen

Degree

Ph.D.

Department

School of Economic Sciences

Advisor

Holly Hong Wang

Start year

2003

Year of completion

2006

Abstract

Publications

Pest Management

Investigations of How Predator Diversity and Prey Behavior Interactively Mediate Community Structure

Name of student

Shawn Steffan

Degree

PhD

Department

Entomology

Advisor

Bill Snyder

Start year

2005

Year of completion

2009

Abstract

Predators may have lethal and/or non-lethal interactions with their prey, and the effects of such interactions may cascade to the resource base on which the prey feed. While it has been documented that increasing predator diversity may improve herbivore suppression, it remains to be resolved whether increasing predator diversity translates into greater non-lethal effects on prey or basal resources. My work examines non-lethal predator-prey interactions, or “fear effects,” within a diverse community of predators attacking larval diamondback moths (Plutella xylostella L.) on collard plants (Brassica oleracea L.). I partition predator effects into lethal and non-lethal components and thereby examine how the effects of predator species richness vary within and across the two components. A pool of five predator species is used to create low and high species richness treatments, and responses are measured in terms of the direct effects on herbivores (density reductions and behavioral changes) as well as the indirect effects of predators on plants (final plant biomass). Recent experiments indicate that plant biomass was greatest where diverse predator assemblages induced anti-predator behaviors in herbivores, an interactive effect not further strengthened when predators could also suppress caterpillar densities. Consistent with these indirect effects on plants, greater enemy richness did not significantly alter caterpillar densities but did induce higher rates of anti-predator behavior. Greater predator diversity, therefore, rendered the enemy assemblages more intimidating but not more lethal. The amplification of fear effects cascaded to benefit plants, suggesting that the effects of predator diversity were primarily transmitted along a non-lethal pathway.

Publications

Lacewings (Chrysoperla rufilabris) Used in Augmentative Release Programs for the Control of Pear Psylla (Psylla pyricola)

Name of student

Robert Curtiss

Degree

M.S.

Department

Department of Entomology

Advisor

John Dunley

Start year

2004

Year of completion

2006

Abstract

Biological control of pear psylla by green lacewing spp; field portions of work take place in organic orchards, and the research is to benefit organic production.

Publications

Microbiology and Effectiveness of Compost Tea for Plant Growth Promotion and Control of Pythium

Name of student

Marjorie Jernigan

Degree

MS

Department

Department of Crop and Soil Sciences

Advisors

Lynne Carpenter-Boggs

Start year

2004

Year of completion

2006

Abstract

Compost teas are increasingly popular with organic growers. This project in collaboration with a regional commercial producer of compost tea equipment tested many parameters of the tea brewing process and products. Compost teas are both a dilute nutrient source and a complex microbial community. Products from open-air continuous-brew systems were found to be less consistent than from overnight single-batch brewing. We tested full-strength and diluted teas, compared to soluble mineral fertilizer, as soil drench on greenhouse petunias, cucumber, and globe basil. Treatment of cucumber and basil with full-strength, ½-strength, or ¼-strength tea gave similar plant growth to the water only treatment, whereas soluble fertilizer produced increased growth. Cucumbers purposely infected with Pythium did not benefit from compost tea treatment. In petunias, soluble fertilizer produced the most blooms but a majority of petunias in this treatment developed interveinal chlorosis. Diluted compost tea (¼ strength) gave similar numbers of blooms with no leaf chlorosis.

Publications

Characterization of compost tea microbial communities, and the effects of compost tea on Xanthomonas campestris pv. campestris pheromone signaling.

Name of student

Catherine Crosby

Degree

MS

Department

Crop and Soil Sciences

Advisors

Lynne Carpenter-Boggs

Start year

2005

Year of completion

2008

Abstract

Recent interest in the use of compost tea as a potential biological disease control agent is based on anecdotal evidence; There is little scientific evidence showing the efficacy if compost tea as an organic disease control agent. In order to further develop compost tea as a biological control agent, first it is necessary to characterize the microbial communities in compost tea. By using terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis, a fingerprint of the community can be generated. This fingerprint can be compared to other compost tea communities, or entered into online databases to find organisms that are most likely to be present. After characterization, compost tea recipes were tested in vitro for inhibition of Xanthomonas campestris, the causal agent of black rot in Brassica crops. X. campestris produces a diffusible pheromone which signals the cells to enter the plant when the population is high enough. If compost tea can interrupt the signaling pathway, then it would have potential applications in the prevention of black rot.

Publications

Evaluation of Seed and Drench Treatments for Management of Damping-Off and Seedling Blight Pathogens of Spinach for Organic Production

Name of student

Jamie Cummings

Degree

MS

Department

Department of Plant Pathology

Advisor

Lindsey DuToit

Start year

2005

Year of completion

2007

Abstract

There are many concerns regarding losses due to soilborne pathogens in organic production systems. The purpose of this research was to evaluate seed and drench treatments for management of soilborne diseases for organic vegetable production. Inoculation rate trials were conducted for three soilborne pathogens, Pythium ultimum, Fusarium oxysporum f. sp. spinaciae, and Rhizoctonia solani, to determine appropriate rates for treatment assessment. Efficacy of treatments was evaluated in the greenhouse against each pathogen using spinach. Treatments included products that were EPA-registered and approved for use in organic agriculture, and products that were being developed for compliance with organic standards. Seed health and germination assays were conducted for each seed treatment to determine potential effects on seedborne fungi, or germination. Selected treatments were evaluated further under field conditions at three locations in western Washington.

Publications

  • Cummings, J.A. 2007. Evaluation of seed and drench treatments for management of damping-off and seedling blight pathogens of spinach for organic production. M.S. thesis, Washington State University, Department of plant pathology.
  • Cummings, J.A., du Toit, L.J., and Miles, C.A. 2008. Evaluation of seed and drench treatments for organic management of soilborne diseases of spinach in western WA. Plant Disease Management Reports 2:submitted in December 2007.
  • Cummings, J.A., du Toit, L.J., and Miles, C.A. 2008. Evaluation of seed and drench treatments for organic management of soilborne diseases of spinach in Sequim, WA. Plant Disease Management Reports 2:submitted in December 2007.
  • Cummings, J.A., and du Toit, L.J. Greenhouse evaluation of seed and drench treatments for organic management of damping-off and seedling blight pathogens of spinach. Plant Disease:manuscript in progress.

Mechanical Weed Management in Conservation Tillage Systems

Name of student

Suzanne Kopan

Degree

MS

Department

Department of Crop and Soil Sciences

Advisor

Robert Gallagher

Start year

2004

Year of completion

2006

Abstract

The focus of the research is on mechanical weed management, and it applies to organic growers as well as those seeking to use integrated management techniques.

Publications

Weed Control in Vegetables and Management of Potato Scab in an Organic Production System in Northwestern Washington

Name of student

Tyler Breum

Degree

MS

Department: Department of Crop and Soil Sciences

Advisors

Tim Miller, Debbie Inglis, Cathy Perillo

Start year

2003

Year of completion

2008

Abstract

Weed and disease management are major concerns for organic farmers, especially during transition; however, research in the development and evaluation of weed and disease control techniques in organic cropping systems is limited. In fall of 2003, a field trial was initiated at the Washington State University Mount Vernon Northwest Washington Research and Extension Center to evaluate the effects of cover crops, organic herbicides, and flaming on two different three-year rotations of potato, spinach seed, cucumber and broccoli. Anticipated outcomes include finding both cultural and chemical strategies to help farmers reduce vegetable crop yield loss due to competition with weeds.

Publications

  • Breum, T.J., C. Steen, and T.W. Miller. Evaluation of organic weed control methods in northwestern Washington. Abstract and poster presentation, Western Society of Weed Science, Portland, OR.

Conservation Biological Control of Cole Crop Pests

Name of student

Renee Prasaad

Degree

PhD

Department

Department of Entomology

Advisor

Bill Snyder

Start year

2001

Year of completion

2005

Abstract

Publications

Entomopathogenic Nematode Efficacy against Colorado Potato Beetle under Organic and Conventional Fertility

Name of student

Ricardo Ramirez

Degree

PhD

Department

Department of Entomology

Advisor

Bill Snyder

Start year

2004

Year of completion

2008

Abstract

The Colorado potato beetle (CPB) is a serious pest of potatoes worldwide. In Washington, organic potato acreage is increasing with few cost-effective CPB control options, while conventional growers rely on broad-spectrum insecticides that may be taken off the market by changing federal regulations. Entomopathogenic nematodes (EPNs) have shown potential as biological control agents against CPB, as one component of integrated pest management (IPM). A survey of endemic EPN populations in the Columbia Basin of Washington revealed that some potato fields under organic and conventional management housed robust EPN populations. Thus, conservation or augmentation of EPNs might improve natural control of the Colorado potato beetle. I will discuss a study examining the ability of EPNs, applied under different rates, within potatoes under organic and conventional fertility. Organic fertility may support soil competitors possibly reducing EPN effectiveness. However, we hypothesize that soil properties associated with increased organic matter may sustain EPN populations over the season. Potato field plots were randomly assigned chemical fertilizer or a chicken and cow manure mixture. During the season, EPNs were applied at zero, low and high rates. EPN infection was monitored with sentinel wax worms and CPB larvae. All treatments were replicated 8 times.

Publications

Plant Breeding

Developing and Testing Breeding Methods for Low Input and Organic Wheat

Name of student

Kevin Murphy

Degree

Ph.D.

Department

Department of Crop and Soil Sciences

Advisor

Steven Jones

Start year

2004

Year of completion

2007

Abstract

In the WSU Organic Wheat Breeding Program, we are growing 160 wheat varieties and evaluating them for traits beneficial to organic farming systems. In addition, we are crossing these historical wheats to our modern varieties and evaluating the subsequent generations. We expect to create and implement the process involved in the long-term evaluation, selection, and eventual release of wheat varieties particularly suited to the organic farmers in the Pacific Northwest. We hope these varieties will increase the number of organic wheat farms in our region and increase the odds of success for these organic farmers. This program was created in response to requests by consumers, farmers and farm organizations for an increase in organic farming research by WSU. The wheat varieties that we breed will also be of interest to conventional farmers interested in more sustainable practices such as a reduced need for herbicides, fungicides and fertilizers. We work closely with farmer-cooperators both for variety testing and for evaluation of useful traits. We place utmost importance on breeding wheat on certified organic farms under the same conditions and systems practiced by the farmer. Our research is designed to benefit the farmer and the public and our varieties will be kept in the public domain.

Publications

Breeding wheat for efficient N use in low-input and organic systems in the Pacific Northwest

Name of student

Julie C. Dawson

Department

Crop and Soil Sciences

Degree

PhD

Advisor

Steve Jones

Start year

2005

Year of completion

2008

Abstract

A field study investigated nitrogen use efficiency (NUE) of wheat in organic systems. There are significant differences in nitrogen cycling between organic and conventional agricultural systems, and the crop traits important to efficient nitrogen use may differ between systems. A diverse range of genotypes were tested, including historic varieties, varieties selected with synthetic nitrogen inputs and varieties selected with only organic nitrogen sources. Also included was a bulk population of perennial wheat. Significant differences were found between wheat varieties selected under different nitrogen regimes for grain yield, grain percent N, total grain N and total biomass yield. In addition, measurements of leaf chlorophyll just after flowering were significantly associated with yield, grain percent N and total grain N. Chlorophyll content was correlated to leaf nitrogen status, and this could be a useful selection criteria in addition to traits measured at harvest. Genotypes with good performance for traits related to NUE can be identified and used for further crossing and selection in organic systems. In the greenhouse, nitrogen uptake and partitioning of annual and perennial wheat genotypes were studied. Historic and modern spring wheat varieties were compared in terms of early nitrogen status, nitrogen in the plant at flowering and nitrogen in the grain and straw at maturity. There were significant genetic differences among genotypes within each experiment. Comparisons showed that historic genotypes generally had greater biomass production at all stages of growth, while modern genotypes had greater N concentrations and a greater harvest index. There was not a significant difference between the categories for grain yield, grain total N, straw N, N uptake, N utilization efficiency or nitrogen harvest index. The role of participatory research was considered in making research results more relevant to low-input and organic systems. A series of grower roundtables were held in counties throughout Eastern Washington. The purpose of these discussions was to interact directly with growers and to get their responses to the open ended questions: What will farming in Eastern Washington look like in 10–20 years? What do growers want it to look like? How can our research help growers get there? In addition, a mail survey of farmers in Eastern Washington was conducted in the fall of 2005; survey questions were developed with the help of several farmers. Results can help us better understand how farmers evaluate new technologies and practices in their production systems, including desirable traits for new wheat varieties, marketing strategies, genetically modified wheat, organic farming, and perennial wheat. The survey also explored differences in management styles; whether farmers are most interested in maximizing production, minimizing inputs, capturing quality premiums, and/or conserving soil and other natural resources. Over 50% of respondents were interested in a participatory wheat breeding project, and results from both the survey and the roundtable discussions are helping us develop ways for farmers to participate more extensively in the Winter Wheat Breeding program.

Publications

Organic Wheat Breeding

Name of student

Kevin Murphy

Degree

M.S.

Department

Department of Crop and Soil Sciences

Advisor

Steven Jones

Start year

2002

Year of completion

2004

Abstract

Publications

  • Murphy, K. and S. Jones. 2003. WSU Organic wheat breeding program. Sustaining the Pacific Northwest Newsletter, Washington State University Extension. Vol 1(1): 2-3. http://csanr.wsu.edu/whatsnew/PNW-v1-n1.pdf
  • Murphy, K., S. Jones, D. Lammer and T. Murray. 2002. The need for organic plant breeding programs, with wheat as an example. Proc. Northwest Symposium on Organic and Biologically Intensive Farming. Nov. 8, 2002, Yakima, WA, p. 39. http://csanr.wsu.edu/programs/Proceedings.pdf Breeding for organic and low-input farming systems: An evolutionary-participatory breeding method for inbred cereal grains.

Plant Nutrient Management

Optimizing nitrogen fixation by improved crop-by-rhizobial strain interactions.

Name of student

Rita Abi-Ghanem

Department

Crop and Soil Sciences

Degree

PhD

Advisor

Dr. Lynne Carpenter-Boggs

Start year

2005 (in Plant Pathology department), 2006 (in CCS)

Year of completion

2009

Abstract

Nitrogen is by far the most common element applied to soils as fertilizer, and still the most common nutrient limiting crop production. Biological N fixation could be used to supply a far greater proportion of the N needed for productive agriculture, improving both environmental and economic sustainability. Increased nitrogen fixation by rhizobial bacteria in symbiosis with grain legumes could have a significant impact on the retention and enhancement of soil productivity for rotational cropping systems found worldwide. The more effective the bacteria-plant symbiosis, the more biological nitrogen is provided to the legume host, to subsequent crops, and to build soil fertility reserves. Less inorganic nitrogen fertilizer is then needed to obtain equal or greater crop production, translating to less leaching potential, improved soil and water quality, lower input costs, and improved profitability, all contributing to greater sustainability of agricultural production. This interdisciplinary project will increase the potential biological nitrogen fixation by selecting for nitrogen fixation capacity on both the microbe and plant sides of the symbiosis. In this project we will develop two critical tools that are leverage points to significant developments in increasing biological N fixation. The first is a matrix of physiological response data from legume breeding lines with many rhizobial inoculants, and the second is a set of specific primers for lentil, pea, and chickpea rhizobia. These will provide the basis for a new emphasis in legume grain breeding for nitrogen fixation, and for in-situ studies of plant-soil-rhizobial interactions.

Publications

Nitrogen Supply and Partitioning in Managed Understories of Organic Apples

Name of student

Lori Hoagland

Degree

PhD; MS

Department

Department of Crop and Soil Sciences

Advisors

Lynne Carpenter-Boggs and John Reganold

Start year

2005

Year of completion

2008

Abstract

Sustainable methods of nitrogen (N) fertility and weed management in organic orchard production systems remain a challenge. Systems are needed that will help reduce N fertility costs, mitigate N loss, and enhance availability at times corresponding with critical tree uptake periods. An integrated study was established in spring 2005 to determine N-use efficiency and optimize fertility guidelines in these alternative systems. Alternative systems included soil tillage, maintenance of a living cover understory, and application of wood chip mulch, brassicaceae seed meal or clove oil herbicide. None of the treatments applied in these studies produced an ideal combination of weed control, tree growth, leaf nutrient content, and improved biological soil quality. Rather, soil quality improvements were achieved at the expense of early tree growth. During establishment of an organic orchard, soil tillage and ample fertilizer amendments are needed to achieve optimal tree health. When the orchard matures and trees are less susceptible to competition, a living cover understory may be a viable strategy to build soil health, reduce N loss and fertility amendment needs.

Publications

  • Hoagland, L., Carpenter-Boggs, L., Granatstein, M Reganold, J.P. (in prep) Managing orchard understory and organic amendments for nitrogen fertility. To be submitted as a Washington state extension publication.
  • Hoagland, L., Carpenter-Boggs, L., Granatstein, D., Mazzola, M., Peryea, F., Smith, J., Reganold, J. (in review). Impact of orchard floor management on nitrogen fertility and biological soil quality in newly established organic apple orchards. Biology and Fertility of Soils.
  • Hoagland, L., Carpenter-Boggs, L., Reganold, J., Mazzola, M., (in press). Role of native soil biology in Brassicaceae seed meal induced weed suppression. Soil Biology and Biochemistry.
  • Hoagland, L., Carpenter-Boggs, L., Granatstein, D., Mazzola, M., Peryea, F., Smith, J., and Reganold, J. (2007). Nutrient cycling and partitioning under alternative organic orchard floor management strategies. In Proceedings, Western Nutrient Management Conference, Salt Lake City, UT. pp 117-123.
  • Hoagland, L., Carpenter-Boggs, L., Granatstein, D., Mazzola., Peryea, F., Smith, J., and Reganold, J. (2006). Nitrogen and carbon cycling and partitioning in managed understories of organic apples. HortScience 41 (4): 1032.

Cover Crops as an Organic Nitrogen Source in Grape

Name of student

Kyle Bair

Department

Crop and Soil Sciences

Degree

Advisor

Joan R. Davenport

Start year

2004

Year of completion

2006

Abstract

Publications

Organic Nitrogen Plant Uptake and Soil Quality Under Organic and Conventional Strawberry Management

Name of student

Jennifer Reeve

Degree

PhD

Department

Department of Crop and Soil Sciences

Advisors

Lynne Carpenter-Boggs and John Reganold

Start year

2004

Year of completion

2007

Abstract

In collaboration with Lynne Carpenter-Boggs, Jeff Smith and Preston Andrews we are investigating possible links between soil quality and fruit quality in organic and conventional strawberry operations. In addition I am investigating the role of organic nitrogen forms in plant nutrition under organically managed systems with the aim to determine whether this is a trait that could be enhanced by selective breeding.

Publications

Development and Use of Compost from Mint Distillery Waste

Name of student

Noah Bonds

Degree

MS

Department

Department of Crop and Soil Sciences

Advisor

Lynne Carpenter-Boggs

Start year

2005

Year of completion

2007

Abstract

Mint is grown and steam-distilled for its aromatic essential oil, leaving over 99.5% of the crop biomass as a waste product. It is not a suitable livestock feed, so the primary disposal routes have been land application or simply piling “in the back 40”. Because of its structure, piled mint tends to self-heat as it decomposes, sometimes to the point of combustion. Smoke from mint waste fires have caused several vehicle accidents and fear of wildfire in central Washington. Although the mint waste does contain plant nutrients, direct land application can cause crop yield reduction at least the first year due to its high carbon content, and possibly due to residual oil. In this project we studied the composting of mint straw and use of the compost as a fertilizer. After composting the material is far less combustive, and total carbon is reduced. Mint compost has a fine texture, pleasant smell, and is easy to work with. However, even after composting, nutrient release was very slow at approximately 10% annual release. Its best use is likely as a horticultural mulch.

Publications

Soil Quality

Cover crop, amendment, and tillage effects on collembolan, nematode, and decomposer communities in an organic vegetable system.

Name of student

Douglas P. Collins

Degree

PhD, Soil Science

Department

Crop and Soil Science

Advisors

Craig Cogger (coadvisor, WSU), Ann Kennedy (coadvisor, USDA-ARS), Hal Collins (USDA-ARS), Tom Forge (Ag Canada)

Start year

2004

Year of completion

2008

Abstract

Two projects are currently under way: 1) Analysis of treatment effects on soil organisms at the Long-term Organic Farming Systems Research and Demonstration Site, WSU Puyallup, and 2) Spatial distribution of edaphic properties
at Full Circle Farm, Carnation, WA.

  1. Soil organisms are sensitive indicators of changes in soil properties. This study reports the effects of different organic management practices on microbial biomass, nematodes and collembolans. Cropping systems treatments are traditional post-harvest, fall-seeded cereal rye-hairy vetch mix; relay-intercropped hairy vetch planted into the standing cash crop; and short-term ryegrass-clover pasture. The two organic amendments are relatively nitrogen-rich chicken manure compost (CKN) and relativel arbon-rich on-farm compost (OFC), primarily yard waste and dairy solids compost. Tillage treatments include intensive conventional plowing and rototilling and a less intense low-speed spader. Microbial biomass was determined with substrate-induce espiration 3 times in 2006 and 2007, nematode community analysis was performed once in 2005 and 2006 and 4 times in 2007, and collembolan diversity was determined 3 times in 2005, 2006, and 2007. CKN amendment caused a marked increase in the numbe f bacterial-feeding nematodes without decreasing omnivorous/predacious or fungal-feeding nematodes. Indices of maturity and community structure were decreased due to CKN at one sampling but the effect was not consistent. Using a slow-speed spade s an alternative to rototilling did not lead to predictable differences in microbial biomass, nematode community indices, or size of collembolan populations. Including a one-year pasture-phase in rotation caused major and significant changes to th icro and mesofauna. Bacterial-feeding nematodes declined by 66–76%, indices of ecosystem maturity and fungal dominance increased significantly, and collembolan populations increased by a factor 3.4–4.5. However, when placed back into cultivatio one of these changes to the soil community persisted.
  2. This project examines the spatial variation of soil organisms and other edaphic properties across a large organic vegetable farm with diverse soil physical properties. Our study site, Full Circle Farm (FCF), is located near Carnation, WA. In 2006 w ampled across a 62-acre area to examine spatial variation of edaphic properties at a farm scale. In 2007 we intensively sampled two separate fields with near identical management to examine spatial variation at a field scale. In 2007 we presente esearch results at a farm walk at FCF (with over 80 participants) and at the WA Tilth Producers Conference. There are five primary objectives for our project: 1) use geostatistics to develop maps for soil organisms and edaphic properties, 2) develo iological indicators that correlate to N-mineralization potential and aggregate stability, 3) recommend general biological sampling methods, 4) make recommendations to optimize farm productivity and profitability, and 5) share results with othe rowers and agricultural professionals.

Publications

  • Collins, D.P., C.G. Cogger, A.C. Kennedy, T. Forge, and A.I. Bary. 2006. Cover crop, amendment, and tillage effects on Collembolans and Nematodes in an organic vegetable system. Soil Science Society of America Abstracts.
    Poster presentation.

Presentations

  • Collins, D.P. 2007. Soil fertility and soil biology: The role of soil organisms in maintaining productive soils. Tilth Producers of Washington Annual Meeting. Yakima, WA.

Soil Quality in Organic Vegetable Cropping Systems

Name of student

Keri Pritchett

Degree

MS

Department

Department of Crop and Soil Sciences

Advisor

Craig Cogger

Start year

2003

Year of completion

2005

Abstract

Publications