Progress 09/15/04 to 08/31/09
Outputs
OUTPUTS: The outputs of the project include studies on N fertility management, pest management, and their interactions, in organic strawberries and broccoli production; economic evaluation of management options developed; and network building among researchers, organic growers, and NGOs for coastal California. We conducted replicated on-farm experiments of organic strawberries and broccoli (2 years/farm x 2 farms for each crop), which provided fundamental information on N management for organic production and how to reduce N losses and environmental impacts. In the broccoli experiments, N release from legume/cereal mixed cover crops for successive broccoli, and relationships between aphid populations and N fertility level were also examined. Data from broccoli experiments were used to calibrate and validate two simulation models, NDICEA and DNDC, by which different management options were evaluated. N fixation by two legume cover crops was estimated using the natural abundance method for use in field level N budgets. The effect of alfalfa trap crops on damage by the western tarnished plant bug (Lygus hesperus) in organic strawberries and its economic implications were examined. Populations of Peristenus relictus, a solitary braconid endoparasitoid of the European tarnished plant bug introduced into California via a quarantine-based testing scheme for host specificity, were monitored at two organic strawberry farms in Monterey County. A cover crop/biofumigation field experiment in Ventura County was conducted to test the effect of biofumigation using mustard 'Ida Gold' on disease severity, crop yield, and soil microbial activity. A series of field and greenhouse experiments were performed to optimize anaerobic soil disinfestation for suppressing Verticillium wilt in organic strawberries. Studies of effects of hedgerow species planted adjacent to annual vegetable systems on the abundance of arthropod natural enemies and pests, dispersal patterns of insects from hedgerows into adjacent crop fields, and parasitism rates between fields with and without hedgerows were conducted in six organic mixed vegetable systems. An on-farm organic strawberry/vegetable rotation experiment was carried out to determine the effects of integrated biological approaches and diverse rotations on strawberry yield, Verticillium dahliae populations in the soil, and soil quality. Major dissemination activities were organic strawberry/vegetable seminar series held in summers of 2006, 2008 (with a field day), and 2009. Twenty to 70 attendants including growers, industry representatives, and researchers came to each seminar presented by project members providing up-to-date information on nutrient management, pest and weed management, disease management, and economics in organic strawberries/vegetables. Other outreach activities include a workshop on organic strawberry/vegetable rotations at the Eco Farm Conference 2008 (>100 attendants), and ALBA-hosted bilingual, practical series in Integrated Pest Management in 2008 and 2009. Finally, two graduate students received Ph.D's from the Department of Environmental Studies, UCSC for their dissertations partially funded by the project. PARTICIPANTS: During the 5-year period, PD Stephen Gliessman (UCSC) oversaw the entire project. He chaired the annual organic network meetings held in January or April of each year. Co-PD Carol Shennan (UCSC) supervised nutrient budget and legume N fixation studies by graduate student Katie Monsen and work on effects of hedgerows on biocontrol by graduate student Tara Pisani Gareau. She also conducted the pre and post project surveys. Co-PD Sean Swezey (UCSC) supervised his research associates, Janet Bryer and Diego Nieto, and conducted studies on cultural and biological control of lygus bugs using alfalfa trap crop/insectaries. Co-PD Joji Muramoto assisted PD Gliessman in coordinating the entire project among participants. Muramoto conducted the strawberry/vegetable rotation study with Gliessman, Koike, Schmida, Shennan, Bull, Swezey and Robert Stephens (Elkhorn Ranch), anaerobic soil disinfestation study with Shennan, Koike, and Leap, and broccoli N fertility trial (the Santa Cruz site) with Leap. Muramoto also coordinated studies on N simulation models with Gerard Oomen, the developer of the NDICEA model, Changsheng Li, the developer of the DNDC model, and Bill Salas (Applied GeoSolutions). Co-PD Steven Koike (UCCE Salinas) conducted Verticillium dahliae tests and disease diagnosis for strawberry studies in the project. Co-PD Richard Smith (UCCE Salinas) implemented N fertility trial for organic broccoli (the Salinas site). Co-PD Mark Bolda (UCCE Watsonville) conducted N fertility on-farm trials for strawberries with Steve Pedersen (High Ground Organics), Kevin Healy (Reiter Associates Inc.), Natalia Neerdaels and Fred Cook (Driscoll's Inc), and Muramoto. He also organized the organic strawberry seminar series in summers of 2006, 2008 and 2009. Karen Klonsky (UC Davis) conducted economic analysis of practices developed in the project. Oleg Daugovish (UCCE Ventura) performed mustard biofumigation study. Mark Gaskell (UCCE Santa Maria) conducted a field trial on N management in organic strawberries in Santa Maria. Carolee Bull (USDA-ARS Salinas) worked on PLFA analysis of soil samples from the rotation trial. Brett Melon, Craig Ficenec, and Chris Goodson (Agriculture and Land-Based Training Association (ALBA)) organized the IPM workshop and field demonstrations at ALBA in 2008 and 2009. Viella Shipley and Jane Baker (California Certified Organic Farmers (CCOF)) helped announce the organic seminar series and assisted dissemination of the outcomes from the project. Sam Earnshaw (Community Alliance with Family Farmers (CAFF)) assisted dissemination of project events. Steve Pedersen (High Ground Organics), Dan Schmida (Sandpiper Farm), Jim Cochran and Tim Campion (Swanton Berry Farm), and Jim Leap (UCSC farm) served as core farmers who consulted on the experimental design, progress, and the direction of the project. Outcomes of each study were presented by the leader of each study at academic meetings, extension meetings, Eco Farm workshop, and organic strawberry/vegetable seminar series. TARGET AUDIENCES: Our target audiences included strawberry and/or vegetable growers who are practicing or interested in organic production, pest control advisors, and representatives from the agricultural industry on the Central to the South Coast of California, the main strawberry and vegetable production areas in the state. Resource-limited and new farmers who speak mainly Spanish were also important target audiences. To disseminate updated information to these people, we collaborated with ALBA, an NGO specialized in outreach to Hispanic growers, consistently providing simultaneous Spanish translation at our workshops and seminars. In 2008 and 2009, ALBA hosted two-part, bilingual, practical series in Integrated Pest Management at its Rural Development Center. The series targeted growers, field managers, and foremen of both large and small operations. Project results were also presented in agroecology courses in the Environmental Studies Department at UCSC, reaching more than 400 students in the course of the project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
In contrast to the previous three seasons, in the last on-farm organic strawberry trial in Watsonville, fruit yield responded significantly to pre-plant fertilizer rates rather than to supplemental N rates. The results appear to be attributed to two factors; a warm and dry winter, and heavier soil at this site. To minimize N loss during the winter without sacrificing fruit yield, therefore, a low to minimum amount of pre-plant N is suggested for sandy soils, whereas modest amounts (~75 lbs-N/acre) of N can be applied for clayey soils. For warm and dry winters, earlier N fertigation may help develop side crowns of strawberry plants, which can later increase fruit yield on the Central Coast of California. In the same study, petiole NO3 concentration showed a much stronger correlation with fruit yield over Total N in the leaf blades. Simulation models NDICEA and DNDC were calibrated and validated by data from two organic broccoli field trials, and initial results suggest there may be a trade-off between high yield and N loss through leaching in this organic system, and that significant N loss during the winter rainy season could take place even with winter cover crops especially at higher preplant N rates. An initial survey of project participants (researchers, extension, growers and NGO representatives) asked what their expectations and motivations were for joining the project. Most expectations centered on building and strengthening research, extension and farmer linkages, and increasing knowledge about organic strawberry and vegetable production. Motivations for participation included the desire to build community, increase opportunities to be involved in collaborations, improve linkages between farmers and researchers, and improve access to and exchange of information. At the end of the project participants were surveyed to see if expectations had been met. Of 18 respondents 15 said it had met or exceeded their expectations, 2 mostly, and 1 that it had partially met them. Participating growers commented that there were many opportunities for interactions with researchers, the project provided useful information, and that it had either reinforced or changed practices used on their farm. Extension agents commented on the successful collaborations and improved knowledge of organic production and the impact it had on growers in the area - "There has been a quantum leap in the knowledge obtained about strawberry fertility. The study has become a standard and is routinely referred to by growers, researchers and industry professionals." Evaluations of seminar series in 2006, 2008, and 2009 by attendants showed that the overall average of rating was "excellent" 64.3% and "good" 35.7%.. Top ten topics requested for future seminars were soil-borne disease management (14.6%), N management (8.3%), fruit quality (8.3%), soil fertility (7.3%), irrigation (6.3%), crop rotation (5.2%), organic pest management (5.2%), organic disease management (5.2%), compost (4.2%), and intercropping of strawberries (4.2%).
Publications
- Brown, M. 2006. Center researchers find pest control help for Central Coast strawberry growers. The Cultivar, Newsletter of Center for Agroecology and Sustainable Food Systems, University of California, Santa Cruz, 24 (1):5-6
- Brown, M. 2007a. Research update: Strawberry pest control research garners federal funding. The Cultivar, Newsletter of Center for Agroecology and Sustainable Food Systems, University of California, Santa Cruz, 25 (1,2):17
- Brown, M. 2007b. Research update: Study on methyl bromide alternatives expands with USDA funding. The Cultivar, Newsletter of Center for Agroecology and Sustainable Food Systems, University of California, Santa Cruz, 25 (1,2):18
- Brown, M. 2008. Research update: ASD examined as potential alternative to methyl bromide. The Cultivar, Newsletter of Center for Agroecology and Sustainable Food Systems, University of California, Santa Cruz, 26 (1):14-15
- Brown, M. 2009a. New tracking method helps researchers design pest control strategies. The Cultivar, Newsletter of Center for Agroecology and Sustainable Food Systems, University of California, Santa Cruz, 27 (1):1-2, 20
- Brown, M. 2009b. Organic research network members present findings at Central Coast workshops. The Cultivar, Newsletter of Center for Agroecology and Sustainable Food Systems, University of California, Santa Cruz, 27 (1):10-12
- Brown, M. 2009c. Research update: Field trials of methyl bromide alternative show promise. The Cultivar, Newsletter of Center for Agroecology and Sustainable Food Systems, University of California, Santa Cruz, 27 (1):14
- Brown, M. 2009d. Research update: New crops at risk grant funds lygus control effort. The Cultivar, Newsletter of Center for Agroecology and Sustainable Food Systems, University of California, Santa Cruz, 27 (1):14-15
- California Certified Organic Farmers (CCOF). 2009. Organic Strawberry Workshop. Education and Promotion. CCOF Certified Organic Magazine, Fall 2009. P.19
- Gaskell, M., Bolda, M., Muramoto, J., and Daugovish, O. 2009. Strawberry nitrogen fertilization from organic nutrient sources. Acta Horticulturae (ISHS) 842:385-388
- Gliessman, S.R. and J. Muramoto. 2009. California (USA) - The Conversion of Strawberry Production. In: Gliessman, S.R. and M. E. Rosemeyer (eds.). The Conversion to Sustainable Agroecosystems: Principles, processes, and practices. Advances in Agroecology Series. CRC Press/Taylor & Francis Group, Boca Raton, FL. pp.117-132.
- Li, C., Salas, W. and Muramoto, J. 2009. Process Based Models for Optimizing N Management in California Cropping Systems: Application of DNDC Model for nutrient management for organic broccoli production. Conference proceedings 2009 California Soil and Plant Conference, 92-98. Feb. 2009
- Monsen, K.L. 2008. Managing nitrogen in organic vegetable agroecosystems on California's Central Coast. Unpublished Ph.D. Dissertation. University of California Santa Cruz
- Muramoto, J., Shennan, C., Fitzgerald, A., Koike, S., Bolda, M., Daugovish, O., Rosskopf, E.N., Burelle, N.K., and Butler, D.M. 2008. Effect of anaerobic soil disinfestation on weed seed germination. Proceedings of the Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions: 109.1-109.3
- Muramoto, J., Smith, R., Leap, J., Ruiz, M. S., Shennan, C., and Gliessman, S. R. 2008. Evaluating Nitrogen Contribution of Mixed Legume/Cereal Cover Crop to the Successive Organic Broccoli (abstract). Annual meetings of the American Society of Agronomy. Houston, TX. Oct. 2008
- Organic Strawberry Manual Committee (ed.) 2010. Organic Strawberry Manual. UC ANR Press. In review.
- Pickett, C. H., Swezey, S. L., Nieto, D. J., Bryer, J. A., Erlandson, M., Goulet, H., and Schwartz, M. D. 2009. Colonization and establishment of Peristenus relictus (Hymenoptera: Braconidae) for control of Lygus spp. (Hemiptera: Miridae) in strawberries on the California Central Coast. Biological Control 49: 27-37
- Pisani Gareau, T. 2008. Farmscaping for conservation: Factors that influence growers' conservation behavior and the potential of hedgerows for enhancing biological control services. Unpublished Ph.D. Dissertation. University of California, Santa Cruz
- Shennan, C., Muramoto, J., Koike, S. T., and Daugovish, O. 2009. Optimizing Anaerobic Soil Disinfestation for Non-Fumigated Strawberry Production in California. Proceedings of the Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions 101.1-101.3
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: An annual organic networking meeting was held on Jan. 23, 2008 to review our progress and discuss the plan for 2008. For outreach, a workshop on organic strawberry/vegetable rotations was conducted as a part of the Eco Farm Conference 2008 on Jan. 24, 2008 at Asilomar, CA. Focusing on the outcomes from the project, five presentations from different perspectives were made by the project members. There were more than 100 attendants in the audience. Power point presentations are available online at: http://www.agroecology.org/Ecofarm08.html. On Apr. 8 and 15, ALBA hosted a two-part, bilingual, practical series in Integrated Pest Management in Salinas in which many of the project members participated as presenters. Topics included agronomic, regulatory, and marketing advantages of using reduced-risk pest management approaches. Twenty-five growers and industry representatives, with influence over management of more than 4000 acres, attended one or both of the workshops. Upon a request from the California Strawberry Commission, an organic strawberry seminar series was organized by the project members and was held in the summer of 2008 in Watsonville, CA. The series consisted of field demonstration of alfalfa trap crops at ALBA (8/27) and seminars on nutrient management (9/3), pest and weed management (9/10), and disease management and economics (9/17) in organic strawberries. Field demonstrations had 12 attendants and two local television stations, one in English and the other in Spanish, broadcasting the event on their local newscast. At each seminar, three to four speakers presented updated information including outcomes obtained from the project to20 to 40 attendants. Simultaneous Spanish translation was provided for all seminars. Evaluation indicated that the series was well received. In Jul. 2008, outcomes of the project were shared at The International Conference on Sustainable Agriculture and Environment 2008 at Sapporo, Japan, as well as multiple seminars held in Japan. On research, N budgets of two local organic farms were calculated using data collected from the project and others. In this we also examined how the choice of %Ndfa estimate affects the balance of N budgets in these systems. A two-year dataset on N dynamics in organic broccoli trials in Santa Cruz and Salinas were compiled. Using the datasets parameterization of simulation model NDICEA was completed and the model DNDC is in progress. Results from organic broccoli trials on the effect of cover crop N to successive broccoli were presented at ASA meeting. The first year of a strawberry trial at the second site in Watsonville with pre-plant application (none, 150, or 300 lbs-N/acre) and supplemental N rate (0, 75, or 150 lbs-N/acre) as treatments was initiated in October 2007 and fruit yield, N dynamics, and mite population were monitored till October 2008. We continued to monitor two organic strawberry farms in Monterey County into which the parasitoid, Peristenus relictus, of the European tarnished plant bug, Lygus rugulipennis, had been released into vacuumed alfalfa trap crops. PARTICIPANTS: PD Stephen R. Gliessman at UCSC oversaw the entire project. He spoke at the workshop on organic strawberry/vegetable workshop in Eco Farm Conference 2008 in Jan. 2008 and at the organic strawberry seminar series in Sep. 2008. Co-PD Carol Shennan at UCSC supervised nutrient budget studies by graduate student Katie Monsen and work on effect of hedgerows in biocontrol by graduate student Tara Pisani Gareau. Co-PD Sean L. Swezey at UCSC supervised his research associates, Janet Bryer and Diego Nieto, and conducted studies on cultural and biological control of lygus bugs and mites using alfalfa trap crop/insectaries. He also gave a talk at the organic seminar series on his study. Co-PD Joji Muramoto assisted PD Gliessman in coordinating the entire project among researchers, growers, and NGOs. He also coordinated and participated in studies on N simulation models, and N fertility trials on organic strawberries and organic broccoli. Dr. Muramoto presented data from the project at the workshop on organic strawberry/vegetable workshop in Eco Farm Conference 2008 as well as the organic strawberry seminar series. Co-PD Steven T. Koike at UCCE Salinas spoke at the workshop on organic strawberry/vegetable workshop in Eco Farm Conference 2008. Co-PD Richard Smith at UCCE Salinas facilitated the workshop on organic strawberry/vegetable workshop in Eco Farm Conference 2008. He also summarized the second-year field trial on effect of N rates on organic broccoli in Salinas. Diego Nieto analyzed the effect of N on aphid population in the same trial. Co-PD Mark Bolda at UCCE Watsonville conducted the field trial on the effect of N rates on organic strawberries at the second site in Watsonville collaborating with Kevin Healy of Reiter Associates, Fred Cook of Driscoll's, and Joji Muramoto. He also organized the organic strawberry seminar series in which he gave three talks. Karen Klonsky at UC Davis spoke at the organic seminar series on economic implications of the rotation trial. Oleg Daugovish at UCCE Ventura gave a talk at the organic seminar series on weed management in organic strawberries. Mark Gaskell at UCCE Santa Maria initiated a field trial on N management in organic strawberries in Santa Maria. Carolee T. Bull at USDA-ARS in Salinas worked on PLFA analysis of soil samples from the organic rotation trial. Craig Ficenec at Agriculture and Land-Based Training Association (ALBA) organized the IPM work shop (April, 2008) and field demonstrations (Aug. 2008) at ALBA. Viella Shipley of California Certified Organic Farmers (CCOF) helped disseminate the outcomes from the project through the CCOF website. Steven Pedersen at High Ground Organics, Dan Schmida at Sandpiper Farms, and Tim Campion at Swanton Berry Farm served as core farmers who consulted the progress and the direction of the project. TARGET AUDIENCES: Our target audiences include strawberry and/or vegetable growers who are practicing or interested in organic production, pest control advisors, and representatives from the agricultural industry on the Central to the South Coast of California, the main strawberry and vegetable production areas in the state. Resource-limited and new farmers who speak mainly Spanish are also important parts of the target audiences. To disseminate updated information to these people, we collaborate with ALBA, an NGO specialized in outreach to the audience, providing simultaneous Spanish translation in our workshops and seminars consistently. On April 8th and 15th, 2008, ALBA hosted a two-part, bilingual, practical series in Integrated Pest Management at its Rural Development Center. The series targeted growers, field managers, and foremen of both large and small operations. Outreach for the events included announcement to nearly 200 Spanish speaking local growers at the annual "Ag Expo" in Salinas, a bilingual color postcard mailing to approximately 500 regional growers and partners in the central coast, and an email announcement to approximately 100 partners. Please see "Outputs" for more information on our outreach efforts. PROJECT MODIFICATIONS: The second site for N management trial in organic strawberries in Watsonville was selected in year 3, a year later than the original plan. The trial is supposed to run for two years at each site. To complete the trial, therefore, no cost extension of the project for one year was requested, which was approved by USDA in July 2008. The new end date of the project is 8/31/2009.
Impacts
A N budget was developed for a seven-year rotation for a vegetable production field at Farm A. Assuming 50% of legume cover crop N was derived from fixation, the field had a total of 799 kg N/ha of inputs and a positive balance of 354 kg N/ha over the 7 yrs and an average annual potential loss of 51 kg N/ha. The N budget for a field at Farm B covered 5 yrs for a total N output of 650 kg N/ha. Assuming 50% of legume cover crop N came from fixation, the total input was 1414 kg N/ha, giving a 5-yr positive balance of 764 kg N/ha, or an average annual potential loss of 153 kg N/ha. Changing the biological N fixation budget from 50 to 95% more than doubled the estimated annual potential loss N from 51 to 129 kg N/ha at Farm A and from 153 to 251 kg N/ha at Farm B. Organic broccoli field experiments at the UCSC farm (organically managed over 30 years. Trial 1) and Salinas site (cover crops have been incorporated for the last several years. Trial 2), indicated that broccoli yield, broccoli-N, and soil mineral N were increased by cover crop applications only in 2006 at both trials and not in 2007 at Trial-2. In Trial-2, the cover crop in 2006 had a greater percentage and total amount of N in the cover crop tops (3.10% and 218 kg-N/ha) than in 2007 (2.07% and 172 kg-N/ha), which was similar to one in Trial-1 (2.08% and 179 kg-N/ha). Although both sites had sandy loam soil, C/N ratio of the topsoil was higher in Trial-2 (TC: 1.39%, TN: 0.11%, C/N: 12.6) than in Trial-1(TC: 1.03%, TN: 0.10%, C/N: 10.1), indicating 1) the importance of having sufficient N in the cover crops to stimulate short-term N release and crop N response, and 2) the availability of N from cover crops may vary depending on soil C/N ratio. A part of the study dealing with organic broccoli N content and aphid infestation was also reviewed, with there being a trend between more N and more aphids at Trial 2, but no differences at Trial 1. This may be due to better bio-control at Trial 1or as a result of the time of year the latter project was carried out. In the first year of organic strawberry field trial at the second site in Watsonville, pre-plant fertilizer rates did not affect fruit yield but supplemental N rate significantly increased marketable fruit yield. This demonstrated again that a pre-plant pelleted organic N fertilizer application, a common practice among local growers, can be significantly reduced or even eliminated without sacrificing fruit yield on the Central Coast. Monitoring in 2007 to 2008 confirmed the establishment in the field of a new parasitoid (Peristenus relictus) and its correlation with lower Lygus populations. These data indicate that P. stygicus has been established as an exotic, new association parasitoid of the Western tarnished plant bug, and can adapt to, over-winter, and colonize organic strawberry production in central coastal California. The parasitoids are also harbored over winter on weedy vegetation in and around fields. There appears to be a density dependent relation between more Lygus and higher rates of parasitism.
Publications
- Brown, M. 2008. Lygus control research extended to conventional systems. Cultivar, Newsletter of Center for Agroecology and Sustainable Food Systems, University of California, Santa Cruz. Vol 26, 1 http://casfs.ucsc.edu/publications/cultivar/26.1.pdf
- Brown, M. 2008. Strawberry-vegetable study confirms value of crop rotations. Cultivar, Newsletter of Center for Agroecology and Sustainable Food Systems, University of California, Santa Cruz. Vol 26, 1 http://casfs.ucsc.edu/publications/cultivar/26.1.pdf
- Gaskell, M., Bolda, M., Muramoto, J., and Daugovish, O. 2008. Strawberry nitrogen fertilization from organic nutrient sources. Acta Horticulturae. In press.
- Gaskell, M., Bolda, M., Muramoto, J., and Daugovish, O. 2008. Strawberry nitrogen fertilization from organic nutrient sources, Small Farm News, Vol. 3 Fall 2008, p.6-7, Small Farm Center, University of California Division of Agriculture and Natural Resources. http://www.sfc.ucdavis.edu/pubs/SFNews/200803news.pdf
- Gaskell, M. and R. Smith. 2007. Organic nitrogen sources for vegetable crops. HortTechnology 17: 431-441.
- Letourneau, D. K., Shennan, C., Bothwell, S. G., and Pisani Gareau, T. 2008. Vegetation Management for Biological Control in Annual Crops: Spatial Scale and Meta-communities. Proceedings in XXIII International Congress of Entomology. Durban, South Africa.
- Monsen, K.L., and Shennan, C. 2007. A tale of two legumes: what can isotopes and models tell us about optimizing N management with legume cover crops in organic vegetable systems Proceedings of the National Conference on Agriculture and the Environment, Nov. 7-9, 2007, Asilomar, CA. CD-ROM
- Muramoto, J. 2008. Agroecological approaches in developing sustainable food systems: A case study of organic research network in California, USA. Proceedings, SGP International Conference on Sustainable Agriculture and Environment 2008, Sapporo, Japan. Abstract
- Muramoto, J., Smith, R., Leap, J., Shennan, C., and Gliessman, R. Nitrogen Contribution to Organic Broccoli from a Mixed Legume/Cereal Cover Crop. Annual meeting of American Society of Agronomy, Nov. 04-07, 2007. New Orleans, LA. Abstract.
- Muramoto. J., Gliessman, S., Shennan, S., Schmida, D., Stephens, R., and Swezey, S. Optimizing Nitrogen Management in an Organic Strawberry Production System on Coastal Central California. 2007. Proceedings of the National Conference on Agriculture & the Environment, Nov. 7-9, 2007, Asilomar, CA, CD ROM
- Pickett, C. H., Swezey, S. L., Nieto, D. J., Bryer, J. A., Erlandson, M., Goulet, H., and Schwartz, M. D. 2008. Colonization and establishment of Peristenus relictus (Hymenoptera: Braconidae) for control of Lygus spp. (Hemiptera: Miridae) in strawberries on the California Central Coast. Biological Control. In press.
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Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: We held an annual organic network meeting in Jan. 2007 and agreed to prepare a proposal for a workshop on organic strawberry/vegetable rotations at Eco Farm Conference 2008. Our proposal was accepted and the workshop was scheduled on Jan 24, 2008. Manuscripts for organic strawberry manual were submitted to UC ANR press for review. Two greenhouse experiments were conducted to improve N fixation estimates for two winter legume cover crops, bell beans (Vicia faba) and woollypod vetch (Vicia dasycarpa) using the natural abundance method. Results were presented at ESA meeting. A two-year dataset on N dynamics in organic broccoli trial in Santa Cruz was compiled. Using the dataset parameterization of simulation models NDICEA and DNDC is in progress. Economic implications of the five-year organic strawberry/vegetable rotation experiment were explored. Results were shared through organic strawberry workshop, NASGA symposium, ASA meeting, Elkhorn research symposium, and Florida
Phytopathological Society meeting. The second year of organic broccoli trial in Salinas with cover crop application (+/-) and organic N fertilizer rate (0, 75, 150 or 225 lbs-N/acre) as treatments was conducted. Results were disseminated through a UC extension event and ASA, CASA, and ASHS meetings. The second year of a strawberry trial in Watsonville with pre-plant application (none, Sudan grass, or compost) and supplemental N rate (75, 150 or 225 lbs-N/acre) as treatments was completed. A demonstration trial at ALBA in Salinas was conducted to examine effect of pre-plant pelleted organic N fertilizer application on fruit yield. The second site for organic strawberry trial in Watsonville was selected. Glucosinolates in three mustard cultivars used for the cover cropping/biofumigation field experiment in Ventura County were determined. Results were presented at ASHS meeting and International Symposium of Sustainable Agriculture. To optimize anaerobic soil disinfestation for
suppressing Verticillium wilt in organic strawberries, we compared the effect of different C sources (none, wheat bran, molasses) on viability of Verticillium propagules in Santa Cruz site. C sources were applied in November and water was irrigated through drip tapes buried in plastic-mulched beds. Populations of Peristenus relictus, a single solitary braconid endoparasitoid of the European tarnished plant bug, Lygus rugulipennis, were introduced into California organic strawberries in 2004, via a quarantine-based testing scheme for host specificity. We continued to monitor two organic strawberry farms in Monterey County into which parasitoids had been released into vacuumed alfalfa trap crops. Results were presented at NASGA symposium. Our studies on 1) effects of hedgerow species planted adjacent to annual vegetable systems on the abundance of arthropod natural enemies and pests, 2) dispersal patterns of insects from hedgerows into adjacent crop fields, and 3) parasitism rates
between fields with and without hedgerows continue in six organic mixed vegetable systems. Results were presented at Pacific branch-ESA meeting, STEPS's Institute workshop, and ESA meeting.
PARTICIPANTS: PD Stephen R. Gliessman at UCSC supervised and coordinated the overall project. He prepared a proposal for a workshop on organic strawberry/vegetable workshop in Eco Farm Conference 2008. Co-PD Carol Shennan at UCSC supervised N fixation and nutrient budget studies by a graduate student Katie Monsen and work on effect of hedgerows in biocontrol by a graduate student Tara Pisani Gareau. She also collaborated with Gerard Oomen, Changsheng Li at Univ. of New Hampshire, Bill Salas at Applied GeoSolutions, Katie Monsen, and Joji Muramoto on simulation model evaluation. Dr Shennan supervised studies on anaerobic soil disinfestation (ASD) for Verticillium wilt in organic strawberries. Co-PD Sean L. Swezey at UCSC supervised his research associates, Janet Bryer and Diego Nieto, and conducted studies on cultural and biological control of lygus bugs and mites using alfalfa trap crop/insectaries. Co-PD Joji Muramoto assisted PD Gliessman in coordinating the entire project among
researchers, growers, and NGOs. He also coordinated and participated in studies on N simulation models, organic strawberry/vegetable rotation, N fertility trials on organic strawberries and organic broccoli, and ASD for organic strawberries. Dr. Muramoto collaborated with UC Cooperative Extension (UCCE) farm advisors (four co-PDs), Sam Earnshaw at Community Alliance with Family Farmers (CAFF), Craig Ficenec at Agriculture and Land-Based Training Association (ALBA), and Viella Shipley at California Certified Organic Farmers (CCOF) for organizing and advertising outreach activities. A demonstration trial was conducted at ALBA by Craig Ficenec and Joji Muramoto. Co-PD Steven T. Koike at UCCE Salinas quantified populations of Verticillium dahliae in the soils and diagnosed pathological diseases in organic crop rotation trial, ASD trial, and N fertility trials. Co-PD Richard Smith at UCCE Salinas conducted the second-year field trial on effect of N fertility on organic broccoli in Salinas.
Diego Nieto examined effect of N on aphid population in the same trial. Co-PD Mark Bolda at UCCE Watsonville led the second-year field experiment on effect of N on organic strawberries in Watsonville collaborating with Steve Pedersen at High Ground Organics and Joji Muramoto. Daniel Schmida at Sandpiper Farms collaborated with Joji Muramoto for data analysis of the rotation trial he managed during 2001 and 2006. Jim Leap at CASFS-UCSC collaborated with Joji Muramoto for data analysis of the organic broccoli trial at UCSC. He also managed an ASD field trial at UCSC farm in 2005-2006. Karen Klonsky at UC Davis analyzed economic implications of the rotation trial and organic broccoli trial. Oleg Daugovish at UCCE Ventura continued work on biofumigation with Brassica cover crops. Mark Gaskell at UCCE Santa Maria participated in designing field trials for organic strawberries. Carolee T. Bull at USDA-ARS in Salinas worked on PLFA analysis of soil samples from the organic rotation trial.
Our collaboration with Kevin Healy at Reiter Associates began in 2006 to conduct N fertility trial on organic strawberries in Watsonville.
TARGET AUDIENCES: Our main target audiences are organic strawberry growers and organic vegetable growers on the South to the Central Coast of California. These areas cover majority of strawberry production acreages in California where approximately 85% of fresh market strawberries in the US are produced. Although current organic production represents only 4% of the total strawberry acreages in the state, this number has been on the rise and more strawberry growers in the state appear to be interested in organic production. Our new collaboration with Reiter associates, one of largest strawberry growers in the country, indicates this trend. Given its highly susceptible character to soil-borne diseases, organic strawberry production must have a crop rotation system. Therefore we decided to organize a workshop on organic strawberry/vegetable rotation in Eco Farm Conference 2008. Results from our 5-year rotation study and related information on organic crop rotation including disease
management, economic implications, and grower's experiences and perspectives will be presented by our project members in the workshop. N dynamics data in two organic strawberries field trials on the Central Coast were presented at multiple seminars for strawberry growers along the coast including Spanish speaking growers on the South Coast. This led a development of a similar trial on the South Coast. Collaborating with ALBA, a demonstration trial on the effect of N fertility in organic strawberries was conducted with a new grower in Salinas. Results will be disseminated specifically to new and resource-limited growers in the area through newsletters and seminars both in English and in Spanish. Further ALBA are planning a two-day workshop for IPM and biocontrol in vegetable and strawberry production in April 2008, in which many of our project members will present results from our studies. The workshop will be advertized through CCOF and CAFFs' extensive networks among organic growers
and family farms throughout California. For more information on our dissemination efforts, please see Outputs and Publications.
Impacts
Greenhouse experiments indicated bell beans and vetch had active nodules early in growth across different fertility levels (0 to 200 kg-N/ha). Estimated %Ndfa by bell beans and vetch ranged from 51 to 91%Ndfa, much higher than a conventional belief of ~50%. This could significantly affect N budget estimates in leguminous cover crop-based agroecosystems on the Central Coast. Organic broccoli field experiments in Santa Cruz and Salinas indicated that 14 to 23% of cover crop N was utilized by the successive broccoli crop. Incorporated cover crops increased broccoli-N in a manner similar to 67 to 90 kg-N/ha of applied organic N fertilizer. In the second year of organic strawberry field trial in Watsonville, as seen in the first year, neither pre-plant fertilizer nor supplemental N rate significantly affected cumulative marketable fruit yield. An organic strawberry demonstration trial at ALBA in Salinas also showed no difference in fruit yield between with and without
pre-plant pelleted organic N fertilizer application plots, suggesting a pre-plant pelleted organic N fertilizer application, a common practice among local growers, may be significantly reduced or eliminated without sacrificing fruit yield on the Central Coast. The cover cropping/biofumigation field experiment in Ventura County demonstrated a reduction in disease severity, increased crop yield, and higher soil microbial activity with biofumigation using mustard Ida Gold. Presence of 4-hydroxybenzyl glucosinolates in roots of Ida Gold and its absence in the other Brassica crops may explain beneficial effects of Ida Gold. A bed-applied ASD significantly reduced Verticillium dahliae population in naturally-infested soils. With this and other promising results, our proposal to optimize ASD in conventional strawberry in California and vegetables in Florida as an alternative to methyl bromide was accepted for funding by USDA-CSREES methyl bromide transition program. Alfalfa trap crops
constitute a large reservoir of parasitoids associated with lower densities in adjacent strawberries. These data indicate that P. stygicus has been established as an exotic, new association parasitoid of the Western tarnished plant bug, and can adapt to, over-winter, and colonize organic strawberry production in central coastal California. Weedy field margins and alfalfa trap crops both form a source/reservoir area for release and subsequent dispersal to organic strawberries. We have 2 years of data on insect abundance at six different hedgerow plants commonly used in hedgerow design: Achillea millefolium, Baccharis pilularis, Ceanothus spp., Eriogonum giganteum, Heteromeles arbutifolia, and Rhamnus californica. We have found that the plants, the bloom period, time of the sample and the particular hedgerow all significantly affect insect abundances for the different taxa. For all 2007 trials we found no significant differences in parasitism rates between hedgerow and non-hedgerow
fields due most likely to the variability in cropping systems, management style, acreage and surrounding landscape across the different sites.
Publications
- Pisani Gareau, T. 2005. Farmscaping with hedgerows in the Central Coast of California: Examining the Potential for Biological Control (abstract). 90th Ecological Society of America Annual Meeting. Montreal, Canada. Aug. 2005.
- Pisani Gareau, T. 2007. Insect natural enemies and pests associated with hedgerow plants established in California vegetable systems (abstract). 91st Annual Meeting Pacific Branch Entomology Society of America. Portland, OR. Mar. 2007.
- Pisani Gareau, T. and Bothwell, S. 2007. Conservation biological control in the Central Coast California: Investigating the influence of on-farm native hedgerows and landscape diversity on arthropod natural enemies. The STEPSs Institute Central Coast Biodiversity Workshop. Santa Cruz, CA. Jan. 2007.
- Pisani Gareau, T., Shennan, C. and Letourneau, D. 2007. Hedgerows: Enhancing conservation biological control potential in California annual vegetable systems? (abstract). 92nd Annual Meeting Ecological Society of America. San Jose, CA. Aug. 2007.
- Smith, R., Muramoto, J., Leap, J., Shennan, S., and Gliessman, S. R. 2007. Nitrogen Uptake by Organic Broccoli from a Legume/Cereal Mix Cover Crop. Hortscience 42:952-953(abstr.).
- Swezey, S. L., Nieto, D. J., and Bryer, J. A. 2007 Control of Western Tarnished Plant Bug Lygus Hesperus Knight (Hemiptera: Miridae) in California Organic Strawberries Using Alfalfa Trap Crops and Tractor-Mounted Vacuums. Environmental Entomology, 36 (6) 1457-1465
- Swezey, S. L., Nieto, D. J., and Bryer, J. A. 2007 Control of Western Tarnished Plant Bug Lygus Hesperus Knight (Hemiptera: Miridae) in California Organic Strawberries Using Alfalfa Trap Crops and Tractor-Mounted Vacuums. North American Strawberry Growers Association Symposium, Ventura, CA. Feb. 2007
- Daugovish, O. 2007. Mustard-Derived Biofumigation for Soil Borne Pests: A Review and Case Studies in California. AGRICULTURA SUSTENTABLE Tecnicas y Productos de Bajo Impacto Ambiental. Published by the International Symposium of Sustainable Agriculture. ISBN: 968-844-045-0. pp. 203-214
- Daugovish, O., A.J. Downer, M.J. Mochizuki. 2006. Mustard-derived Biofumigation for Lettuce in Coastal California. Proc. 2nd Int. Biofumigation Symp., Moscow, Idaho, June 2006.
- Daugovish, O., A.J. Downer, M.J. Mochizuki. 2007. Mustard-derived Biofumigation for Lettuce in Coastal California. Hortscience 42:953 (abstr.).
- Gliessman, S. R. 2006. Presentation to Curso de Experto, Universitario en Produccion Ecologico, El Cultivo Ecologico del Freson (Organic Production of Strawberries). Universidad de Sevilla, Andalucia, Spain, March 3.
- Gliessman, S. R. 2007. Conversion of a strawberry production system. IN: Gliessman, S.R. Agroecology: Ecology of Sustainable Food Systems. 2nd Edition. CRC/Lewis Taylor & Francis Group, Boca Raton, FL. Pages 292-295.
- Gliessman, S. R. 2007. Transitioning to Sustainable Strawberry Agroecosystems. North American Strawberry Growers Association Symposium (NASGA), Ventura, CA. Feb. 2007.
- Monsen, K. L., and Shennan, C. 2005. Estimating Biological N Fixation in Vegetable Production Systems with Annual Legume Inputs (abstract). Agronomy Society of American Annual Meeting. Salt Lake City, UT. Nov. 2005.
- Monsen, K. L., Shennan, C. and R.S. Schneider. 2005. Estimating Biological N Fixation in Agroecosystems with Annual Legume Inputs. Ecological Society of America Annual Meeting. Montreal, Quebec. Canada. Aug. 2005.
- Monsen, K. L., and Shennan. C. 2006. Incorporating N Fixation Uncertainty into Nitrogen Budgets for Organic Vegetable Agroecosystems (abstract). Ecological Society of America Annual Meeting. Memphis, TN. Aug. 2006.
- Monsen, K. L., and Shennan. C. 2006. Incorporating N Fixation Uncertainty into Nitrogen Budgets for Organic Vegetable Farms (abstract). World Congress of Soil Science. Philadelphia, PA. July, 2006.
- Monsen, K. L., and Shennan. C. 2006. Nitrogen Fixation by Central Coast Winter Cover Crops: Is Natural Abundance Appropriate? (abstract). California Plant and Soil Conference. Visalia, CA. Feb. 2006.
- Monsen, K. L., and Shennan. C. 2007. Lazy Legumes or Busy Beans? High N fixation Rates of Winter Cover Crops across Soil Fertility Levels. Ecological Society of America Annual Meeting. San Jose, CA. Aug. 2007.
- Muramoto, J. 2007. Anaerobic Soil Disinfestation: an Alternative to Chemical Fumigation for Strawberries? 6th Annual Strawberry Production Meeting in Ventura County. Camarillo, CA. Aug. 2007.
- Muramoto, J. 2007. Nitrogen Management and Integrated Verticillium Wilt Management in Organic Strawberries. Organic Strawberry Workshop. Co-sponsored by State Water Resources Control Board, Prop. 50, NCAT, California Strawberry Commission, UCCE-Ventura Co., Santa Barbara Co. and CASFS-UCSC. Summerland, CA. Mar. 2007.
- Muramoto, J. and Smith, R. 2007. Release of Nitrogen from Cover Crops and Impacts on Organic Broccoli Fertility. Irrigation and Nutrient Management Meeting, UCCE-Monterey Co., Salinas, CA. Feb. 2007.
- Muramoto, J., Gliessman, S. R., Koike, S. T., Shennan, C., Schmida, D., Stephens, R., and Swezey, S. L. 2007. Maintaining Agroecosystem Health in an Organic Strawberry/Vegetable Rotation System. North American Strawberry Growers Association Symposium, Ventura, CA. Feb. 2007.
- Muramoto, J., Gliessman, S. R., Koike, S. T., Shennan, C., Schmida, D., Stephens, R., and Swezey, S. L. 2007. Maintaining Agroecosystem Health in an Organic Strawberry/Vegetable Rotation System: The Final Result (abstract). Elkhorn Slough Research Symposium, Moss Landing, CA. Jan. 2007.
- Muramoto, J., Gliessman, S. R., Koike, S. T., Shennan, C., Schmida, D., Stephens, R., and Swezey, S. L. 2006. Maintaining Agroecosystem Health in an Organic Strawberry/Vegetable Rotation System (Part 5): The Final Result (abstract). Annual Meeting of American Society of Agronomy, Indianapolis, IN. Nov. 2006.
- Muramoto, J., Smith, R., Leap, J., Shennan, C., and Gliessman, S. R. 2007. Nitrogen Uptake by Organic Broccoli from a Legume/Cereal Mix Cover Crop (abstract). Annual meeting of California Chapter American Society of Agronomy. Sacramento, CA. Feb. 2007.
- Pasakdee, S.J., Banuelos, G., Shennan, C., and Cheng, W. 2007. Organic N fertilizers and irrigation influence organic Broccoli production in two regions of California. Journal of Vegetable Science 12:27-46.
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Progress 10/01/05 to 09/30/06
Outputs
In 2006 we held two organic network meetings, a field day, and three seminars on fertility, soil-borne disease and insect pest management in organic strawberries. The seminar series was well attended (40-70 for each) and well received by local growers and industry people. We developed a prototype of N budgets spread sheet and handout, and continue our efforts to improve estimates of N fixation by two legume cover crops using the natural abundance method. Parameterization of simulation models NDICEA and DNDC is underway using locally collected data sets of cover crops, broccoli, and strawberries. We completed the five-year organic strawberry/vegetable rotation experiment in Moss Landing. It demonstrated that under low Verticillium pressure, using a combination of ecological practices enabled strawberries to be grown in a 1 to 3 year-break rotation without significant yield difference from a 7 year-break rotation. Organic broccoli trials with cover crop application
(+/-) and organic N fertilizer rate (0, 75, 150 or 225 lbs-N/acre) as treatments were conducted in Santa Cruz and Salinas. In both sites, yield of broccoli was significantly increased by the rate of organic fertilizer N and cover crop application. N uptake by broccoli indicated cover crop incorporation provided 37 and 27 lbs-N/acre to broccoli biomass in Santa Cruz and Salinas, respectively. Fertility treatments had no effect on cabbage aphid (Brevicoryne brassicae) abundance on broccoli, but broccoli harvest rate was higher in Santa Cruz where 10 times more predacious syrphid larvae were found than in Salinas. The first year of a strawberry trial in Watsonville with pre-plant application (none, feather meal, or compost) and supplemental N rate (50, 100 or 150 lbs-N/acre) as treatments was also completed. Neither pre-plant fertilizer nor supplemental N rate significantly affected marketable fruit yield, probably due to pre-plant cover crop incorporation across all treatments. Thus for
the second year trial in Watsonville, we varied both pre-plant application (none, cover crop, or compost) and supplemental N rate (75, 150 or 225 lbs-N/acre). The cover cropping/biofumigation field experiment in Ventura County demonstrated a reduction in disease severity, increased crop yield, and higher soil microbial activity with biofumigation using mustard 'Ida Gold'. To optimize anaerobic soil disinfestation for suppressing Verticillium wilt in organic strawberries, we compared the effect of different C sources (none, wheat bran, molasses) on viability of Verticillium propagules. We continued to monitor two organic strawberry farms where parasitoids had been released into vacuumed alfalfa trap crops. At one farm, average seasonal western tarnished plant bug, Lygus Hesperus, nymphal density in strawberries has declined each year since the release of parasitoids in 2004. Our studies on 1) effects hedgerow species planted adjacent to annual vegetable systems on the abundance of
arthropod natural enemies and pests, 2) dispersal patterns of insects from hedgerows into adjacent crop fields, and 3) parasitism rates between fields with and without hedgerows continue in six organic mixed vegetable systems.
Impacts
Developing practical strategies for fertility/pest management in organic farming and strengthening the networks among organic farmers and researchers in California will increase the knowledge base and the flow of information among researchers and farmers as well as increase the viability, sales and acreages of organic crops in California. Ultimately, this will further contribute to sustainability of California agriculture by reducing dependence on synthetic pesticides and fumigants, conserving biodiversity, protecting surface/ground water quality, improving soil health and nutrient cycling, and enhancing the quality of life of growers and consumers. Specifically, results from the fertility trial in organic strawberries demonstrated that significant reduction in pre-plant N fertilizer is possible without sacrificing fruit yield. This will decrease growers' production costs and improve organic N fertilizer use efficiency, by which impacts on the environment through N
leaching and run-off will be reduced.
Publications
- Pasakdee, S.J., G. Banuelos, C. Shennan and W. Cheng. 2007. Organic N fertilizers and irrigation influence organic Broccoli production in two regions of California. Journal of Vegetable Science (In Press)
- Swezey, S.L., D. Nieto, and J. Bryer. 2007. Control of western tarmished plant bug, Lygus hesperus, Knight (Hemiptera: Miridae) in California organic strawberries using alfalfa trap crops and tractor-mounted vacuums. Environmental Entomology (In Review)
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Progress 10/01/04 to 09/30/05
Outputs
We had three organic network meetings during the first year. Since most project participants are able to attend meetings, it was decided that the Project Team and Network Advisory Board would be the same group. A pre-project assessment was conducted by semi-structured interviews with project participants. A newly created email list serve has been extensively used among members throughout the year. We continued to collect data on nutrient budgets from three local organic farms. Work on improving estimates of N fixation by four legume cover crops using the natural abundance method was continued. Simulation models NDICEA and DNDC are being parameterized by locally collected data sets of mustard, organic broccoli, and organic strawberries. We completed the 4th year of the five-year organic strawberry/vegetable rotation experiment. Numbers of Verticillium dahliae microsclerotia in soils were frequently reduced after broccoli residue incorporations, whereas no such
reduction was observed after mustard incorporation. By limiting the preplant compost application rate, N loss during the rainy season from the strawberry plots was reduced to 10% of the previous year's level without sacrificing fruit yield. We established three replicated N fertility/pest monitoring trials for broccoli and strawberries. An organic broccoli trial with compost application (0 or 5 tons/acre) and organic N fertilizer rate (0, 75, 150 or 225 lbs-N/acre) as treatments was conducted in Santa Cruz. Yield of broccoli was significantly affected by the rate of organic fertilizer N (P=0.004) but not by compost. Although cabbage aphid (Brevicoryne brassicae) abundance was generally greater on plants that were given more N, parasitism and predation were substantial enough to provide biological control, regardless of application rate, in the highly diverse organic farm. Another organic broccoli trial with similar design is being conducted in Salinas in a less diverse environment. An
organic strawberry trial in Watsonville is in progress. Cover cropping/biofumigation field experiment in Ventura County is in progress. A series of field and greenhouse experiments were conducted to optimize anaerobic soil disinfestation for suppressing Verticillium wilt in organic strawberries. Significant reduction of V. dahliae microsclerotia in recovered inoculants was observed in anaerobic treatment (mortality 98%. P=0.0001). When soil Eh was reduced to -100mV during the first week, 6 weeks of anaerobic treatment was sufficient to reduce V. dahliae to non-detectable level. Twice-weekly summer vacuuming treatment of alfalfa trap crops reduced damage due to the western tarnished plant bug (Lygus hesperus) in associated organic strawberries by an average of 25% compared with the organic strawberry grower's standard whole-field vacuuming treatment. The overall positive return for the three months of trap cropping treatments was calculated at +$648/acre. Work examining influences of
the diversity of hedgerow plant species planted on the borders of annual vegetable systems on the presence and abundance of arthropod natural enemies and pests is in progress in five organic mixed vegetable systems.
Impacts
Developing practical strategies for fertility/pest management in organic farming and strengthening the networks among organic farmers and researchers in California will increase the knowledge base and the flow of information among researchers and farmers as well as increase the viability, sales and acreages of organic crops in California. Ultimately, this will further contribute to sustainability of California agriculture by reducing dependence on synthetic pesticides and fumigants, conserving biodiversity, protecting surface/ground water quality, improving soil health and nutrient cycling, and enhancing the quality of life of growers and consumers.
Publications
- Brown, M. 2005a. Research update: Anaerobic residue digestion offers promise for Verticillium control. The Cultivar 23 (1):10-11.
- Brown, M. 2005b. Research update: Strawberry/vegetable rotation study gives clues to nutrient and disease management. The Cultivar 23 (1):9-10.
- McNulty, J. 2004. USDA grant funds research with central coast organic farmers. The Cultivar 22 (2):1-3.
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