Anaerobic Soil Disinfestation; Its agroecological significance in California strawberry production

Transcription

1 Anaerobic Soil Disinfestation; Its agroecological significance in California strawberry production Session 2: Organic agriculture and scale: Balancing environmental and consumer demands Food, Agriculture and Human Impacts on the Environment: Japan, Asia and Beyond, November 6-7, 2017, UC Berkeley JOJI MURAMOTO DEPT. OF ENVIRONMENTAL STUDIES UNIVERSITY OF CALIFORNIA, SANTA CRUZ

2 Outline California strawberries: conventional and organic Anaerobic soil disinfestation (ASD) Agroecological significance of ASD in CA strawberries

3 California Strawberries $1.9 billon values in % of world production ~85% of US production 15,765 ha in 2014 by ~300 growers San Francisco Santa Cruz Precip. mm Santa Cruz, CA ( Normal) Air temp. C Av. yield: 70 tons/ha Year-round harvest Los Angeles Month

4 Chemical fumigation Methyl bromide + chloropicrin Control soilborne disease and weeds, increase yield Core technology for the large-scale mono-cultural strawberry production for the last 50 years (Wilhelm and Koch, 1956)

5 Ozone Hole and Montreal Protocol Ozone layer: Earth s sun screen protects people, plants, and animals from ultraviolet radiation Skin cancer is the most common cancer in the US 1992: Methyl Bromide added to Montreal Protocol 2005: 100% phase out with limited exemptions in developed countries 2016: Expiration of Critical Use Exemption

6 Residential proximity to methyl bromide use during the second trimester was associated with markers of restricted fetal growth Although critical use exemptions for methyl bromide use are being phased out, the lack of fumigant alternatives may prolong its use in the state of California.

7 Organic/Conventional Comparative On-Farm Strawberry Experiment at the Swanton Berry Farm (Gliessman et al., 1996)

8 4,500 Organic Strawberry Acreage in California ,000 Acres 3,500 3,000 2,500 2, % of total strawberry acreage in CA Costco 1,500 1,000 Walmart/Whole Foods 500 CSA/Farmers markets/local natural food stores Year (California Strawberry Commission)

9 Outbreak of Verticillium wilt at CASFS farm, UCSC in 2001 and 2002

10 Anaerobic Soil Disinfestation (ASD) Developed in the Netherlands and Japan independently ~2000 as a biological alternative to fumigation Principle: Acid fermentation in anaerobic soil Four-step process 1. Incorporate labile C-source 2. Moisten the amended soil 3. Cover by plastic mulch to limit oxygen supply 4. Maintain anaerobic decomposition (Van Bruggen, 2014) (Chiba prefecture, 2002)

11 Picture of paddy-upland mixed farming in Nara, Japan. Circa Paddy-Upland Rotation: > 400 years of history in Japan (Tokunaga, 1997)

12 Temperature Crop genotype Anaerobiosis Organic acids Soil type /management history? Pathogen Water Microbial shifts Depth and time C source Type & Rate ASD Management Triangle (Shennan et al, 2014)

13 Anaerobic Soil Disinfestation (ASD) in California strawberries 1. Broadcast rice bran at 9 tons/acre 2. Incorporate bran 3. List beds 4. Cover w/ plastic mulch 5. Drip irrigate total 1 to 2 ac-in over 3 wks 6. Leave 3 wks and monitor soil Eh (redox potential)

14 ASD provides comparable fruit yield with fumigant

15 ASD-treated strawberry fields in California 80% organic sites 20% conventional sites ~20% of CA organic strawberry acreage ~2.5% of CA total strawberry acreage

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17 Agroecological Evaluation of ASD 1. Optimize use of locally available resources Partial replacement of rice bran with cover crop

18 Use of cover crop as a partial C-source for ASD ASD-Standard: rice bran 13 t/ac Aerobic Anaerobic ASD-CC: Sudan grass 1.4 tons-d.w./ac + rice bran 6 t/ac Use of freshly mowed cover crop with reduced rate of rice bran created a stronger anaerobic condition than the standard ASD

19 Agroecological Evaluation of ASD 1. Optimize use of locally available resources Partial replacement of rice bran with cover crop 2. Minimize losses of soil, nutrients, water and energy N 2 O emission, NO 3 -N leaching evaluation in progress 3. Optimize soil conditions for plant growth Tactical use of rice bran, wheat bran to supply nutrients 4. Promote genetic and species diversification Increased soil fungal diversity

20 Effect of treatments on number of fungal taxa and diversity of the community, determined by analysis of terminal restriction fragment length polymorphism data of DNA from soils of strawberry field trials at the Watsonville site, 2011/12 OTU: Operational taxonomic unit Shannon H: Shannon s diversity index (Shennan et al., 2017)

21 Agroecological Evaluation of ASD 1. Optimize use of locally available resources Partial replacement of rice bran with cover crop 2. Minimize losses of soil, nutrients, water and energy N 2 O emission, NO 3 -N leaching evaluation in progress 3. Optimize soil conditions for plant growth Tactical use of rice bran, wheat bran to supply nutrients 4. Promote genetic and species diversification Increased soil fungal diversity 5. Favor beneficial interactions and synergies among agrobiodiversity components Integration of crop rotation, genetic resistance, and ASD

22 Integrated Soil Health Management (ISHM) for Organic Production (Concept) Targets Crop Yield Market Ecosystem services Site-specific ISHM Location specific Knowledge intensive Soil health diagnosis Traditional/Molecular-base biological test Soil microbial community Beneficial/pathogenic microbes Diversity, keystone species Physical, biochemical and chemical tests Selecting practices Variety Crop rotation/cover crop Soil amendment/fertilizer Compost, MSM, chitin. ASD (C-source options) Production

23 Conclusions ASD: agroecological practice based on the principle of acid fermentation in anaerobic soils Reducing external C-source and costs may be accomplished by using cover crops/crop residues ASD increases soil fungal diversity Environmental impacts: N 2 O gas emission, NO 3 -N leaching need further studies Future non-fumigant systems in CA and beyond will be location specific and require integration of crop rotation, genetic resistance, and other tactics such as ASD

24 Thank you! Question?