- Fruits: berries (strawberries)
- Vegetables: broccoli, cauliflower
- Crop Production: crop rotation, cover crops, fallow, fertigation, irrigation, nutrient cycling, organic fertilizers, tissue analysis
- Education and Training: extension, networking, on-farm/ranch research, participatory research, workshop
- Farm Business Management: budgets/cost and returns
- Pest Management: biological control, economic threshold, field monitoring/scouting, mulching - plastic
- Production Systems: organic agriculture
- Soil Management: green manures, soil analysis, nutrient mineralization, organic matter
- Sustainable Communities: ethnic differences/cultural and demographic change
Continued growth of organic strawberry and vegetable production in coastal California faces major challenges, namely soil-borne disease management without the use of chemical fumigants (especially for Verticillium wilt caused by Verticillium dahliae); efficient nutrient management to prevent spring and fall leaching losses; and high costs for weeding. In conventional systems, due to stringent regulations and air quality concerns, the sustainability of chemical fumigant dependent systems is uncertain.
A team of researchers, growers, farm advisors and NGOs will tackle these issues by testing combinations of three non-chemical approaches: anaerobic soil disinfestation (ASD, an ecological alternative to methyl bromide fumigation), broccoli residue incorporation and mustard cake application. Using fields highly infested with V. dahliae, we will conduct replicated split-plot experiments with three-year rotations:
2) cauliflower-strawberries-lettuce, and
3) fallow-strawberries-lettuce as main plots;
and ASD, mustard cake, ASD plus mustard cake and untreated control as split plots at one organic and one conventional farm.
Split plot treatments will be applied prior to strawberry planting. An additional fumigant control split plot treatment, (Pichlor 60) will be used in the conventional site. Verticillium dahliae populations in soil, weeding time, degree of wilt symptoms, soil-plant N dynamics and crop yields will be monitored and net returns will be evaluated. Further on-farm experiments will determine the optimum rate of mustard cake for weed and disease suppression and N release for organic strawberries and lettuce.
Outcomes will be disseminated through workshops, pamphlets, field trips, YouTube, eOrganic, extension publications, academic journals and newsletters. A demonstration field will be established at the Agriculture and Land-Based Training Association (ALBA), an NGO assisting limited-resource and aspiring growers.
Project objectives from proposal:
Objective 1: To test the effects of ASD, broccoli residue incorporation, mustard cake (MC) application, alone and in combination, on crop yields, V. dahliae suppression, weed suppression, N provision, production costs and net returns in strawberries and lettuce grown in typical crop rotation systems on organic and conventional farms with high V. dahliae pressure (Shennan, Muramoto, Koike, Klonsky, Milazzo, Olivera, Tanimura, Noma and Kimes. Yrs 1-3, Santa Cruz, Salinas).
1. The modes of action of ASD and Brassica biofumigation are different, therefore the combination of ASD and biofumigation from MC and/or broccoli incorporation will provide superior disease suppression compared to either ASD alone, or MC and broccoli incorporation alone or together.
2. Mustard cake will be more effective at disease suppression than broccoli incorporation when used alone or in combination with ASD due to the higher levels of isothiocyanates produced by the MC.
3. Rotations with broccoli will be more disease suppressive than those with cauliflower or bare fallow.
4. The combination of ASD, broccoli residue incorporation and MC application will provide equivalent strawberry and lettuce yields and disease control as the standard chemical fumigation treatment.
5. Among non-chemical approaches, only treatments containing MC will provide significant weed suppression for the subsequent strawberry crop.
Strawberry crop: improved yields; reduction in soil V. dahliae populations, plant wilt symptoms, weed biomass and weeding time; and an increase in net income increase for the systems that integrate ASD, broccoli and MC incorporation as compared to single practice treatments and the untreated control. In the conventional trial, the target is for the integrated system to perform comparably to the chemical fumigation treatment based upon the measures listed above.
Lettuce crop: Based on literature and previous data from our ASD work, we do not expect weed suppression by any treatment to carry beyond the strawberry crop. Our goal with the Verticillium sensitive lettuce crop is to establish whether disease suppression from treatments applied before planting strawberries is maintained into the next cropping season and is sufficient for good yields to be obtained without additional pathogen control measures. If it is, this will make the economics of using ASD and MC in particular more attractive and allow for more diverse strawberry/vegetable rotations.
Objective 2: We propose a series of additional experiments to optimize MC application procedures for improved yields, weed and disease suppression and N provision in strawberries and Romaine lettuce. Specific goals are 1) to establish the optimum time between MC application and lettuce planting; 2) test the effects of MC application rate, depth of incorporation and level of preplant fertilizer on yields, disease and weed suppression in lettuce production; 3) as for goal 2 but for strawberries and 4) assess the economic feasibility of MC use in lettuce and strawberries (Shennan, Muramoto, Koike, Olivera, Klonsky, Pedersen and Kimes. Yrs 1-3, Watsonville).
1. Providing adequate time is left between MC incorporation and planting to prevent phytotoxic effects, MC application will provide effective weed and disease suppression, enhance yields and meet preplant N requirements for strawberries and lettuce.
2. Shallow incorporation of MC (1”) will provide better weed suppression than deeper incorporation (6”), but disease suppression will have the opposite response.
3. Given the current high price ($0.8/lbs as of November 2010) of MC, its utility may be restricted to high value crops such as strawberries unless the price drops in the future*, or it provides substantial benefits in terms of yield increase, weed suppression and/or disease suppression.
Demonstrate effective weed and disease suppression (of both V. dahliae and Sclerotinia minor) from MC application. Identify optimal rates, application methods and adjustment of preplant N input to devise the most cost effective and nitrogen conserving options for lettuce and strawberry production (Note: results from the first strawberry trial (objective 2.3) will be available in time to inform our choice of MC application rate and fertility management in the rotation experiment under objective 1. This trial is already established using money from the Organic farming Research Foundation grant).
*The price is expected to fall somewhat as biofuel production from mustard oil increases.
Objective 3. To disseminate results to growers and agricultural professionals in coastal CA and beyond through a variety of approaches including workshops, a field demonstration (at an NGO farm that works with low resource Hispanic organic farmers), field trips, YouTube, eOrganic and written materials (All team members. Yrs 2 and 3).
Our goal is to stimulate significant interest in integrated use of ASD, broccoli and MC incorporation for disease and weed control, as measured by grower participation at workshops and field trips, number of growers wanting to test the systems after the workshops and field trips and numbers of growers seeking information through eOrganic and accessing the YouTube videos. Our information dissemination targets are to reach 350 growers through the Community Alliance for Family Farmers newsletter, contact 500+ Spanish speaking growers through ALBA, reach more than 3,000 readers through the Center for Agroecology & Sustainable Food Systems (CASFS) newsletter, and the majority of the 600 conventional and organic strawberry growers in CA through working with the California Strawberry Commission to disseminate information. Agricultural professionals will be targeted through these same outlets as well as via electronically available CASFS research briefs, the project website, workshops, regional, national and international professional conference presentations.