1. Optimizing Drip Fumigation through Deep Application and Totally Impermeable Film Covering for Strawberry Production Ruijun Qin, Oleg Daugovish, Suduan Gao, Brad Hanson, James Gerik and Husein Ajwa

2. Raised-bed strawberry production California strawberries are grown mainly in raised-bed systems tarped with standard polyethylene film (PE). Over 55% of strawberry fields are treated with fumigants applied through drip irrigation lines buried near the bed surface (drip fumigation) prior to planting. Two major issues on the drip fumigation practice: –Fumigant emissions impair air quality and result in environmental hazard. –Unsatisfactory pest control at bed-center or bed-shoulder, especially at deep depths.

3. Totally impermeable film (TIF) shows great potential in reducing emission and improving pest control efficacy in flat field with shank-fumigation. Applying fumigant deep may have a lower emission than applying shallow. Information on the performance of TIF covering and deep-applied fumigant via dripping lines in raised-bed systems is limited.

4. Objective Develop effective fumigation strategies that increase fumigation efficiency, sustain strawberry production, and reduce environmental pollution by TIF covering and deep drip-fumigation in raised-beds of the coastal regions.

5. Field trial (2013 - 2014)  Location: Strawberry field in Camarillo (coastal area of Southern CA)  Soil: Sandy loam  Bed configuration: 119 cm (bed width), 35 cm (bed height), 175 cm (bed center-center).  Distance of drip lines: 68 cm  Dripping depth: 5 cm (shallow) & 18 cm (deep).  Fumigant: Pic-Clor 60 EC (a mixture of 56.7% CP, 37.1% 1,3-D, and 6.2% inert ingredients).  Application rate: 300 lbs/ac(full rate) vs. 150 lbs/ac (1/2 rate)

6. Treatments 1)Two shallow drip lines - non-fumigation under TIF 2)Two shallow drip lines - full rate under TIF 3)Two shallow drip lines - 1/2 rate under TIF 4)Four drip lines (2 shallow & 2 deep) - full rate under TIF 5)Four drip lines (2 shallow & 2 deep) - 1/2 rate under TIF 6)Two shallow drip lines – full rate under PE * 24 tarped beds including 6 treatments and 4 replicates. ** PE plots and TIF plots are not at same location.

7. Measurement During fumigation period (Aug. 16-Aug. 30): –Emission (passive chamber): Full rate TIF treatments (bed and furrow). –Fumigant concentration under film above soil surface (AU). –Fumigant gas in soil profile. –Pathogen survival at the end of fumigation. After fumigation and throughout crop season (Late September, 2013 – late June, 2014): –Plant growth. –Berry production.

8. Fumigant emission from bed Deep- vs. shallow-application:

9. Fumigant emission from furrow Deep- vs. shallow-application:

10. Fumigant concentration under film Center Edge Center Edge

11. Fumigant gas in soil profile: Bed center: 10, 20, & 30 cm Bed-edge: 10, 20, 30, 40, & 50 cm Furrow: 10 & 20 cm near the bed bottom. Deep fumigation tapes 10 cm 20 cm 30 cm 40 cm 50 cm 10 cm 20 cm 10 cm 20 cm 30 cm 6 h & 1, 2, 4, 7, 10, 13 d

12. Fumigant concentration time exposure index

13. Pest control on buried pathogens Buried Fusarium oxysporum was detected in non-fumigated beds, especially at the bed- center. All the fumigation treatments provided 100% control, both at bed-center or near bed edge.

14. No difference was found among TIF treatments. Plant cover on bed Canopy size Leaf greenness Stomatal conductance 11/27/2013 1/24/2014 5/2/2014 Strawberry growth

15. Marketable berry yields during 8 harvest from January 30 to March 18 were slightly higher in deep fumigation treatments. In general, no significant berry yield was found throughout crop season. * The measurement was on 20 plants per beds. Strawberry yield

16. SUMMARY Low emissions occurred from the TIF mulched raised-bed systems. TIF retained fumigants more effectively than PE; half- rate fumigant under TIF may achieve same pest control result as full rate fumigant under PE. Deep application provided better emission control and contributed to more uniform fumigant distribution than shallow application. Data on pest control, plant growth, and berry yield further suggest that deep fumigation and TIF covering will be the optimized fumigation technology in raised-bed production systems.

17. Questions on deep fumigation technique For the bed-configuration (119 cm W x 35 cm H): –What’s the best application depth? How about 10-15 cm? –How to improve fumigant distribution at bed center? Shortening drip tape distance? Deep tapes: –Sufficient water and nutrients for younger plants. –Nutrient leaching. –Used tape removal. Other bed configuration (lower or narrower)

18. ACKNOWLEDGMENT The grant from the Walmart Foundation and administered by the University of Arkansas System Division of Agriculture Center for Agricultural and Rural Sustainability. The grant from California Department of Food and Agriculture Specialty Crop Block Grant Program. Cooperating growers, Steve Imoto, Glen Imoto, and their field crew providing the tested field, field equipment, and field preparation. Crop Production Service (CPS) provided fumigation service. Technical assistance was provided by Water Management Research Unit, USDA-ARS, Parlier, CA and the Department of Plant Sciences, UC Davis. Fumigation service and equipment was provided by Crop Production Service (CPS).

19. Thank you Ruijun (Ray) QIN University of California-Davis/ USDA-ARS 9611 S. Riverbend Ave., Parlier, CA 93648 Tel: 559-596-2904 Cell: 559-905-9286 Email: ruijun.qin@ars.usda.gov