This material is based upon work that is supported by the National Institute of Food and Agriculture, under award number 2014-51181-22382. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

http://biodegradablemulch.org

Biodegradable Plastic Mulch for Weed Control and Crop Quality

Shuresh Ghimire and Carol Miles

Department of Horticulture, Washington State UniversityNorthwestern Research and Extension Center,

Mount Vernon, WA

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Photo: Tina Zhang, 2015

• Weed management

• Conserves moisture

• Warms soil in spring

• Hastens time to harvest

• Increases yield

• Reduces erosion

• Increases crop quality

• More efficient use of water and fertilizer

• Reduces soil compaction

• Efficient double or triple cropping

Polyethylene (PE) mulch use in agriculture

3

• Projected PE mulch use globally in 2017: 1.4 million tons (Agricultural Films Market Global Trends and forecasts to 2017).

• Projected PE mulch use in North America in 2017: 117,700 tons (24% increase from 2011) (Agricultural Films Market Global Trends and forecasts to 2017).

• Limited recycling options for used PE mulch

1. Up to 50% (by wt.) contamination with soil and debris

2. Many landfill do not accept plastic mulch

Current scenario of mulch use

4

Photo: Tina Zhang, 2015

Photo: Greg Scullin

• Need for removal and disposal

• Removal and disposal cost is $237 per acre (Galinato et al., 2012)

• Generally not all plastic is removed from the soil

• Residuals may decrease soil productivity

• Issue of sustainability

• Overall environmental hazard

Problems with PE mulch

Photo: Greg Scullin

Biodegradable plastic mulch

Has the potential to be a sustainable technology if it:

• Provides benefits equal to PE mulch

• Reduces labor costs for removal and disposal

• Completely biodegrades

• Causes no harm to soil ecology or the environment

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This material is based upon work that is supported by the National Institute of Food and Agriculture, under award number 2014-51181-22382. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

http://biodegradablemulch.org

Performance and adoptability of biodegradable plastic mulch for

sustainable specialty crop production

Funded by USDA-NIFA through Specialty Crop Research Initiative (SCRI)

Experiments at Mount Vernon WA, and Knoxville TN

Project design

• Sites: Mount Vernon, WA and Knoxville, TN

• 7 treatments replicated 4 times

• 5 rows per plot, 30 ft long row

• 2015 & 2016: ‘Cinnamon Girl’ pie pumpkin

• 2017-2018: sweet corn (WA)peppers (TN)

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2015 & 2016 BDM experiment

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Mulch products in experiment

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Treatment ManufacturerThickness

(mil)Bio-based %

Bare ground

BioAgri BioBag Americas, Inc. Dunedin, FL 0.7 20-25%

Exp.PLA/PHA Experimental Film 1 86%

Naturecycle Custom Bioplastics, Burlington, WA 1 ≥ 20%

Organix Organix Solutions, Bloomington, MN 0.7 10-20%

Polyethylene (PE) Filmtech, Allentown, PA 1 < 1%

WeedGuardPlus Sunshine Paper Co., Aurora, CO 9 100%

Data collection

• Percent soil exposure (PSE)

• Weed count and weight: 2 weeks after transplanting both years, and mid-season and late season 2015 only

• Yield: weight and number of total and marketable fruit

• Post-harvest fruit storage & quality evaluation every 2 wks for 8 wks:

➢Weight loss

➢Soluble solids

➢Dry weight

• Mulch biodegradation

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Results

Percent soil exposure (PSE)

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5% 40%

Percent soil exposure (PSE)

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Days after mulch laying

Weed control

Predominant weeds in TN:1. Nutsedge (penetrated all

the mulches except WeedGuardPlus)

2. Carpetweed3. Goose grass4. Annual bluegrass5. Crabgrass

Predominant weeds in WA:1. Pigweed2. Chickweed 3. Grass (assorted)

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Weed control

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(g)

Total pumpkin fruit yield (2015 & 2016)

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17

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Number of pumpkin fruit per ha (2015 & 2016)

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Mount Vernon Knoxville

Mulch adhesion

Marketable

Storage quality assessment

• Post-harvest fruit storage & quality evaluation every 2 wks for 8 wks:

➢Fruit size

➢Total soluble solids

➢Dry weight

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Pumpkin fruit size at harvest (WA & TN, 2015 & 2016 combined)

19

0

4

8

12

16

20

Fru

it s

ize

(cm

)

Length

Width

P = 0.18 for LP = 0.12 for W

Total soluble solids (0-8 wk storage) (WA & TN combined)

20

TS

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°Bri

x)

cab abc ab ab a bc

1

3

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2015

2016

P = 0.54 for 2015P = 0.02 for 2016

Total soluble solids (0-8 wk storage)(WA & TN, 2015 & 2016 combined)

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TS

S (

°Bri

x)

P = 0.04

ba ab ab b

0

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0 2 4 6 8

Storage weeks

Summary

• PSE was very low for all the products both years except Naturecycle and WeedGuardPlus in 2015

• Minimal weeds in all mulch treatments throughout the season

• Marketable pumpkin yield with all plastic mulches was similar except Organix at Mount Vernon, whereas yield did not differ due to treatment at Knoxville

• High mulch adhesion both years in Mount Vernon except for PE and Exp. PLA/PHA

Summary

• Pumpkin fruit size did not differ due to mulch treatment.

• TSS in 2015 did not differ due to treatment.

• In 2016, TSS was highest for all plastic mulches, intermediate for WeedGuardPlus, and lowest for bare ground.

• Overall, TSS increased from harvest to 2 weeks of storage, then declined until 8 weeks (same level as wk 0).

• Mulch adhesion can reduce marketable yield.

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• Made with conventional plastic: high density polyethylene (HDPE), low density PE (LDPE), polypropylene (PP), polystyrene (PS), polyethyleneterephtalate (PET), polyvinylchloride (PVC)

• Includes additives that promote oxidation of the material, triggered by UV light, heat, and oxygen: Pro-oxidant additive containing (PAC) plastic

• Product becomes brittle and fragments

• Independent third party standard ASTM& ISO test data show small percent or no film fragments utilized by soil microorganisms

• Micro and macro plastics from oxidative degradation build up on land and ocean environments, absorb toxins, and can be transported up the food chain

Oxo-degradable Plastic

3 years after mulch application, Everett, WA Photo by Andy Bary

• FTC concludes company making false and unsubstantiated claims about oxo-products

• Designed to degrade very slowly: <2% in 2 years

• Does not undergo biodegradation

• Not suitable for composting or anaerobic digestion

• Recommend prohibition of sales into markets where plastics are recycled:

o Reduces quality of plastics recyclate

o Cannot be identified and separated

Oxo-degradable PlasticOxo-fragmentable Plastic Mulch

• Not biodegradable and not compostable

• Degradation triggered by UV light and/or heat, limited by moisture

• Degradation occurs over decades or longer

• Microplastics accumulate in the environment

• Certification tests provide no pass/fail criteria: no time limit, no percent degradation

• Ban proposed in the EU due to environmental pollution

• Ellen MacArthur Foundation with 150+ organizations refute claims

of oxo biodegradables and ask for ban

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Oxo-fragmentable Plastic Mulch

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Acknowledgementswww.biodegradablemulch.org

This material is based on work supported by the National Institute of Food and Agriculture, under award number 2014-51181-22382. Any opinions, findings, conclusions or recommendations expressed in this presentation are those of the

author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

Douglas Hayes (PD), Annette Wszelaki, Jennifer DeBruyn, Markus Flury, Eric Belasco, Sean Schaeffer, Arnold Saxton, Susan Schexnayder, Margarita Velandia, Larry Wadsworth, Mark Fly, Carol Miles, Debra Inglis, Thomas Marsh, Jessica Goldberger, Suzette Galinato, Chris Benedict, Jeremy Cowan, Peter Tozer, Andy Bary, Lydia Tymon, Courtney Lyons, Jennifer Moore, Amy Salamone, Babette Gunderson, Ed Scheenstra, Jacky King, Marie English, Sreejata Bandopadhyay, Nurul Farhana Omar, Shuresh Ghimire, Henry Sintim, Kuan Chen

USDA SCRI Project No. 2014-51181-22382