Current Research in Farming Systems and Agroecological Science

    Anaerobic Soil Disinfestation (ASD) to Control Soilborne Diseases in Strawberries

  • ASD was developed in the Netherlands and Japan independently and through the work of UCSC researchers and their partners is being optimized for California strawberries. The first successful ASD trial in the US was conducted at the CASFS farm to control Verticillium wilt in organic strawberries in 2003. In the 2019-20 season, about 2,000 acres of strawberries and cane berries in California and small acreages in Baja California, mostly organic fields, are being produced using ASD. ASD controls soilborne pathogens by creating a fermentation process in anaerobic soil. During the fermentation process, volatile organic compounds, organic acids, and Fe2+ and Mn2+ ions are produced, and a shift in the soil microbial community occurs causing soilborne pathogens to be suppressed.

    Several studies funded by grants from the US Department of Agriculture (USDA) and the California Strawberry Commission allowed us to optimize ASD for California strawberries. ASD is performed in three steps. First, incorporate a labile carbon source into the soil to feed indigenous soil microbes. Typically, 6 to 9 tons/acre of rice bran from Northern California is used as a carbon source in our region. Second, quickly cover the soil with plastic mulch to limit oxygen supply and gas exchange. Third, drip-irrigate 1.5 to 2 acre-inches of water to start and maintain the three weeks' fermentation process. The soil under the tarp will be kept at moist to wet moisture conditions during the treatment. 

    Additional funds have expanded this initial work to examine the use of cover crops and crop residues as a partial carbon source to reduce the costs and external inputs, and develop thresholds to suppress major lethal soilborne pathogens in strawberries including Verticillium dahliae, Macrophomina phaseolina, and Fusarium oxysporum f. sp. fragariae by ASD. A 2017 grant of $2.5 million from the USDA are expanding this effort to locations in Florida, North Carolina, and Tennessee to help fine tune ASD and integrate the ASD with crop rotation and use of resistant cultivars as a non-fumigant soilborne disease management strategy in different climate zones and crops. A 2020 USDA grant will examine suppressive crop rotation using alliums and Summit 515 wheat with and without ASD.

    Read about the 2017 USDA Grant to expand ASD research

    Read about the 2020 USDA Grant to examine suppressive crop rotation

    Watch a video about the CalCORE project to improve organic vegetable and strawberry rotation systems in the Monterey Bay region

    Watch a video about the ASD

    CASFS/UCSC participants: Joji Muramato, Carol Shennan, Darryl Wong, Margherita Zavatta, Jan Perez. Collaborators: Peter Henry (USDA), Rachael Goodhue (UCD), Mark Bolda (UCCE), Oleg Daugovish (UCCE), Chris Greer (UCCE),  ALBA, Driscoll’s, Naturipe, the Oppenheimer Group. Funding: U.S. Department of Agriculture.

    Selected related publications:
    Muramoto, J., Shennan, C., Mazzola, M., Wood, T., Miethke, E., Resultay, E., Zavatta, M., Koike, S.T., 2020. Use of a summer cover crop as a partial carbon source for anaerobic soil disinfestation in coastal California. Acta Horticulturae 1270, 37-44.

    Rosskopf, E., Gioia, F.D., Hong, J.C., Pisani, C., Kokalis-Burelle, N., 2020. Organic Amendments for Pathogen and Nematode Control. Annu. Rev. Phytopathol. 58, 277-311.

    Shennan, C., Muramoto, J., Baird, G., Zavatta, M., Nobua, B., Mazzola, M., 2020. Effects of crop rotation, anaerobic soil disinfestation, and mustard seed meal on disease severity and organic strawberry production in California. Acta Horticulturae 1270, 63-70.

    Shennan, C., Muramoto, J., Koike, S., Baird, G., Fennimore, S., Samtani, J., Bolda, M., Dara, S., Daugovish, O., Lazarovits, G., Butler, D., Rosskopf, E., Kokalis-Burelle, N., Klonsky, K., Mazzola, M., 2018. Anaerobic soil disinfestation is an alternative to soil fumigation for control of some soilborne pathogens in strawberry production. Plant Pathology 67, 51-66.

    Shennan, C., J. Muramoto, M. Mazzola, D. Butler, E. Rosskoph, N. Kokalis-Burelle, K. Momma, Y. Kobara, J. Lamers. 2014. Anaerobic soil disinfestation for soil borne disease control in strawberry and vegetable systems: Current knowledge and future directions. Acta Horticulturae 1044:165-175.

  • No-Till Agriculture in Organic Specialty Crops

  • This 5-year project will examine the impact of no-till agriculture on crop productivity, carbon sequestration, and farm revenues. CASFS has an opportunity to take a lead role in research and leadership around no-till practices for specialty crops. Given that 53% of the nation’s organic fresh fruits and vegetables are grown in California, moving towards sustainable no-till practices here could have a significant national impact on agriculture and food production, while reducing agriculture’s negative contributions to climate change (Klonsky, 2010).

    Beginning in 2018, this project will proceed over five years and in two phases. Phase 1, beginning in year 1 and lasting 30 months, entails a thorough analysis of no-till experiments in organic specialty crops on commercial farms around the country and a review of relevant literature on no-till projects in specialty crops. Data will be collected on soil and input characteristics on 6-10 no-till, specialty crop microfarms across the country. These data would look at traditional soil analyses (soil organic matter [SOM]%, N, P, K, pH, cation, % saturation) at varying depths, and nutrient analysis of inputs to assess the nutrient production potential of these soils and the nutrient load applied. These data will be compared to the same values in native soils and other tilled farm operations in their respective regions to assess carbon sequestration potential. This quantitative analysis will be paired with in-depth grower interviews to understand the specific production practices on each farm. Farm agronomic and economic data will also be collected, including crop yields, debt-to-income ratios, gross sales and expenditures (including labor costs), and net income.

    Practices from the case-study farms will be used to design and implement Phase 2 of the project, using innovative new practices from across the country as well as implementing a transition period for the soil before the actual planting of a no-till crop. 

    In Phase 2 of the study, Wong will compare the effects of three treatments in a replicated field trial on a quarter-acre plot at the UCSC Farm: no-till, reduced tillage, and the standard CASFS tillage practices, using mustard as a winter cover crop prior to a romaine crop, and buckwheat as a summer cover prior to a broccoli crop. Data collected will include soil carbon at various depths, SOM%, and soil bulk density, as well as crop yields. For details of the study design, see the 2018 year-end report. This phase will continue for 3 cropping seasons, beginning in winter 2018.

    CASFS/UCSC participants: Darryl Wong Funding: Ida and Robert Gordon Family Foundation

    Related articles:
    • Grant supports farm research
    • No-till study underway at the UCSC Farm

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