This document summarizes a study on improving fumigant efficiency and reducing emissions in raised-bed strawberry production systems. The study compared different plastic mulch and fumigant application methods. Key findings were that using totally impermeable film (TIF) mulch and applying fumigants deeper through drip lines led to lower emissions, more uniform distribution of fumigants in soil, and slightly higher strawberry yields, while providing equivalent pest control compared to traditional polyethylene mulch and shallow applications. The optimized fumigation method was concluded to be deep application under TIF mulch.

1. Improving Fumigant Efficiency and
Reducing Fumigant Emission in
Plastic Mulched Raised-Bed
Systems 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 prior to planting.
• Soil fumigation is an important tool in controlling soil-
borne pathogens, nematodes, and weeds.
• Use of fumigants are highly regulated by governmental
agencies because of fumigant emissions.

3. Pest problems of strawberry production
• Increasing number of
pathogen-infested fields
and areas.
• Weed problem.
• Difficulty in controlling
pests at bed-center or
shoulder.

4. Plastic film
• Traditional tarp:
– Polyethylene tarp (PE)
• Low permeable tarp:
– Virtually Impermeable Film (VIF)
– Totally Impermeable Film (TIF)
• Tarp permeability:
– PE > VIF > TIF
VIF
TIF

5. Fumigation in raised-beds
• Can totally impermeable film (TIF) covering and/or deep
application improve fumigant distribution, fumigation
efficacy, and reduce fumigant emission?
• Will the emission from the uncovered furrow be a
concern? If true, can water seal control the emissions
from furrow.
2 in
7 in
Drip lines

6. 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.

7. Field trial
 Time: August 16-30, 2013
 Location: Strawberry field in Camarillo (coastal area of
Southern CA)
 Soil: Sandy loam
 Bed dimension: 47 inch W, 14 inch H.
 Bed center-center: 69 inch.

8. Field set-up
Setting up beds
Fertilization
Firming beds
Installing drip tape
Two drip tapes
Four drip tapes

9. 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
* Deep drip lines at 7 inch deep spaced 27 inch in apart beneath shallow
drip lines installed at 2 inch deep.
** 24 tarped beds including 6 treatments and 4 replicates.
** PE plots and TIF plots are not at same location.

10. Drip fumigation
• Fumigant: Pic-Clor 60 EC (a mixture
of 56.7% CP, 37.1% 1,3-D, and 6.2%
inert ingredients).
• Full rate: 25 gallon/ac (300 lbs/ac).
• Application: On August 16 over a 4-h
period.
• Flushing and water seal.
Surface two drip tape
Four drip lines

11. Measurement during fumigation
• Emission (passive chamber): Full rate TIF treatments
(bed and furrow).
• Soil gas sampling.
• Fumigant concentration under tarp.
• Residual fumigant at the end of trial.
• Pathogen survival.

12. Fumigant emission
• Deep- vs. shallow-application:

13. Averaged fumigant concentration under film

14. Fumigant distribution in soil

15. Fumigant concentration time exposure index
(g cm-3 h-1)

16. Pest control
• Fusarium was detected
in 3 non-fumigated beds,
especially at the bed-
center.
• All the fumigation
treatments provided
100% control on
fusarium, both at bed-
center or near bed edge.

17. Strawberry transplantation
• One month after
fumigation.
• Early flowering strawberry
variety, San Andreas
(Lassen Canyon Nursery,
CA).
• The planting intensity:
25,000 plants/ac.
• 4 rows of plants/bed.
• Irrigation and fertilization
was applied regularly to
promote plant growth.

18. No difference was found on plant growth
among TIF treatment during the early
growth stage.
Plant cover on bed
Canopy size
Leaf greenness Stomatal conductance
11/27/2013
1/24/2014
5/2/2014

19. Marketable berry yields
during 8 harvest from
January 30 to March 18
were slightly higher in
deep fumigation
treatments.
* The measurement was on 20 plants per beds.

20. Sumarry
• 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.

21. Outreach activities
• Regular communication with the cooperating growers, the principle
stakeholders (e.g., California Strawberry Commission, Trical, Inc.).
• Annual International Research Conference on Methyl Bromide
Alternatives and Emissions Reductions on November 4-6, 2013 in San
Diego, CA.
• Organic Strawberry Workshop on January 21, 2014 in Tennessee State
University.
• California Plant & Soil Conference on February 4-5, 2014, in Fresno, CA.
• Field day entitled “Water management in strawberry” on March 26, 2014
in Ventura, CA.
• Central Coast California Association of Pest Control Advisers (CAPCA)
Chapter’s Spring CE Meeting on May 1, 2014, at Santa Maria, CA.
• Ventura CAPCA members meeting on June 11, 2014, San Paula, CA.
• American Society for Horticultural Science Annual Conference on July
27-August 1, in Orlando, FL.
• ASA, CSSA & SSSA International Annual Meetings on November 2-5,
2014 in Long beach, CA

22. Acknowledgment
• This project is funded by a grant from the Walmart
Foundation and administered by the University of
Arkansas System Division of Agriculture Center for
Agricultural and Rural Sustainability.
• 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.

23. 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