EcoFarm Conference 2008

Transcription

1 A Five-Year Organic Strawberry/Vegetable Rotation Experiment on Central Coastal California EcoFarm Conference 2008 J. Muramoto 1, S. R. Gliessman 1, S. T. Koike 2, C. Shennan 1, D. Schmida 3, R. Stephens 4, C. T. Bull 5, K. Klonsky 6 and S. L. Swezey University of California-Santa Cruz, 2 University of California-Cooperative Extension, 3 Sandpiper Farms, 4 Elkhorn Ranch, 5 USDA-ARS, Salinas, 6 UC Davis

2 Challenge: Soil-Borne Disease Management without t Use of Chemical Fumigants. Verticillium wilt caused by Verticillium dahliae. A wide range of host crops including lettuce, tomatoes, potatoes, t cauliflower, artichokes, apple, cotton, and strawberries. Resilient overwintering structures can survive for several years without host plants Requires rotating land out of fhost crops for 5 years or more

3 Santa Cruz Monterey Bay Elkhorn Ranch Project Moss Landing Elkhorn Ranch. Moss Landing, CA. 120 acres of certified organic fields. Adjacent to Elkhorn slough national estuarine research reserve. Grower & the landowner proposed the project and instigated the collaboration. A systems approach by multidisciplinary researchers. Agroecologists, plant pathologists, soil scientist, entomologist, t ag-economist

4 Elkhorn Ranch 1 km Elkhorn Slough National Estuarine Research Reserve

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6 Goal To demonstrate effects of diverse organic strawberry/vegetable rotations o and integrated ecological og ca practices on agroecosystem health.

7 Integrating Ecological Practices Compost application. Biofumigation with mustard cover crop and broccoli residues. Crop rotation ti with vegetables that t do not host Verticillium dahliae. Use of relatively resistant strawberry cultivar. Integrated

8 Hypothesis The use of non-host rotation crops for Verticillium wilt plus bio-fumigation with broccoli, mustard or other crop residues and compost application will suppress disease development sufficiently to grow strawberries in rotation ti every 3 years without t sacrificing i fruit yield and negatively affecting soil microbial diversity.

9 On-Farm Rotation Experiment Randomized block design with four replicates. 5 year rotation study ( ). Main plot (n=5): number of years between strawberry crops. Split plot (n=2): strawberry cultivar. Plot size: 91.3m 2 x 20 plots. Total area: 0.19 ha.

10 Main Treatment of the Rotation Experiment Treatment Year 1 Year 2 Year 3 Year 4 Year 5 A (0 yr.*+ br.res.) st st st st st B(1 yr.*) st cc-vegs-st t cc-vegs-st t C (2 yrs.*) cc-vegs-st cc-vegs--cc-vegs-st D (3 yrs.*) st cc-vegs-cc-vegs--cc-vegs-st E(C (Control) cc-vegs-cc-vegs-cc-vegs--cc-vegs-st t Number of years between strawberry crops. br.res.: applying broccoli residues before planting strawberries. cc-vegs: cover crops and vegetables (spinach and broccoli). st: strawberries.

11 Soil Characteristics Soil type: Santa Ynez fine sandy loam, 2t to 9 percent slopes (fine, montmorillonitic, thermic Ultic Palexerolls) with low SOM content (~1 %) in the topsoil. Thick claypan below ~40cm from the surface. Low leaching potential. No major soil chemical problems such as low ph and high EC. Very few Verticillium dahliae propagules in the topsoil.residual effect of fumigation?

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16 Plant Pathological Diagnosis at the End of the Fifth Year Regardless of treatment, no major strawberry pathogens (Phytophthora, Verticillium, Colletotrichum) were recovered from any of the samples. A few plants had the following fungi (all from cv. Aromas): Cylindrocarpon, Pythium, Fusarium (secondary type) --- Sub-lethal pathogens? Soil analysis by PLFA and molecular biological methods are in progress --- Difference in soil microbial communities?

17 Trt. A Trt. B Yr.1 Yr. 2 Yr.3 Yr.4 Yr.5 Yr. 1 Yr. 2 Yr. 3 Yr. 4 Yr. 5 (St) (St) (St) (St) (St) (St) (M+V) (St) (M+V) (St) Trt. C Trt. E Yr. 1 Yr. 2 Yr.3 Yr.4 Yr. 5 Yr. 1 Yr. 2 Yr. 3 Yr. 4 (M+V) (St) (M+V) (M+V) (St) (M+V) (M+V) (M+V) (M+V) Yr. 5 (St) St: strawberries. M: mustard. V: vegetables. Changes in Numbers of Verticillium dahliae Microsclerotia in Soils in Different Treatments. The mean ± SEM. Broccoli residues or mustard incorporation.

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19 Conclusions In organic production systems, under low Verticillium pressure and by using the integrated ecological practices, strawberry cultivar Aromas and Seascape can be grown in 1 to 3 year-break rotation without statistically significant yield difference from 7 yearbreak rotation. Fruit yield difference observed among different rotations in the final year appears to be attributed not to Verticillium dahliae but to other factors such as "none-lethal" pathogens that were not monitored in the experiment and/or improved soil N fertility in longer rotation plots.

20 Conclusions Under low disease pressure, broccoli residues incorporation appears to sufficiently suppress soil Verticillium dahliae population to grow strawberries organically. Analysis of the effect of different rotations on soil microbial diversity by PLFA and molecular biological methods are in progress. Net returns under different rotations with varied break periods between strawberries will be estimated.

21 Funding Support North American Strawberry Growers Association Alfred Heller Endowed Chair, UCSC The Halliday Foundation Center for Agroecology and Sustainable Food Systems, UCSC Organic Farming Research Foundation USDA Integrated Organic Program # The Central Coast Regional Water Quality Control Board Non-point Source Pollution Fund of the Community Foundation for Monterey County California Strawberry Commission