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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

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Biodegradable Mulch: Another Tool to Add to

Your Production Toolbox

Annette Wszelaki1, Jennifer Moore1, Shuresh Ghimire3, and Carol Miles2

1Department of Plant Sciences, University of Tennessee2Department of Horticulture, Washington State University

3Department of Extension, University of Connecticut

Benefits of Plastic Mulch

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H.Y. Sintim, M. Flury, 2017, Environmental Science and Technology 51:1068-1069

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Problems with Plastic Mulch

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Biodegradable Plastic Mulch

Has the potential to be a sustainable technology if it:• Provides benefits equal to

polyethylene mulch• Reduces labor costs for removal

and disposal• Reduces landfill waste• Biodegrades completely• Causes no harm to soil ecology

or environment

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What does biodegradable mean?

• Capable of being broken down via microbial activity

• Biodegradation provides C source for the growth and reproduction of microorganisms

• Complete biodegradation (i.e., mineralization) refers to the oxidation of the compound to CO2 + H2O

Source: Numata, 2009

Slide courtesy of Ghimire and Miles, 2015.

Biodegradable Mulch Ingredients

1 Abbreviations: PBAT polybutylene adipate terephthalate; PBS polybutylene succinate; PBSA PBS-co-adipic acid; PCL polycaprolactone; PHA polyhydroxyalkanoate; PLA polylactic acid; TPS thermoplastic starch

2 Estimated relative rate of biodegradation; Brodhagen et al. 2015. Biodegradable plastic agricultural mulches and key features of microbial degradation. Appl Microbiol Biotechnol (2015) 99:1039–1056.

Ingredient1 Feedstock  Synthesis ERBD in soil2

Cellulose Biobased Biological High

PBAT Hydrocarbon Chemical Low moderate

PBS Hydrocarbon Chemical Low moderate

PBSA Hydrocarbon Chemical Low moderate

PCL Hydrocarbon Chemical Moderate

PHA  Biobased Biological Moderate high

PLA Biobased Biological  & Chemical Low

Sucrose Biobased Biological High

TPS/Starch Biobased Biological High

Slide courtesy of Miles and Ghimire, 2015.

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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

• Product becomes brittle and fragments• Oxo-degradable certification tests provide

no pass/fail criteria: no time limit, no percent degradation

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

Oxo-degradable Plastic

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

Slide courtesy of Miles, 2017.

Production Considerations

• Machine laying the BDM• How long do you want it to last?• More careful handling• Weed Control• Potential for mulch adhesion

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Tips for Laying

• Manufacturers know their products best and willing to help- talk to them!

• Can be laid with same equipment as polyethylene, but laying speed may need to be reduced

• Take the tension off- you want the wheels to guide the laying but not put pressure on mulch

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How long do you want it to last?

• Thickness (mil) tailored to length of time crop will be in field

• Also, differences in performance/ degradation due to climate

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More Careful Handling

• BDM covered beds cannot be walked on like polyethylene covered beds

• More care when working close to the bed edge

• Breakdown at soil edge as season progresses to be expected

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What information is lacking?

• Performance data over multiple years, multiple crops, multiple environments

• Better understanding of biodegradation of commercially available mulches in different climates

• Information on mulch accumulation after multiple applications

• Technology to measure mulch biodegradation in soil

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Pumpkin Trials

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Project Design

• Two locations: Knoxville, TN & Mount Vernon, WA• ‘Cinnamon Girl’ pie pumpkin• 30 ft plots of 5 rows each, replicated 4 times• Seeded direct: 6/16/15 & 6/15/16 Knoxville• Transplanted: 5/28-29/15 & 5/31/16 Mt. Vernon• Harvested: 9/14/15 & 9/6/16 Knoxville;

9/16/15 & 9/21/16 Mt. Vernon• Seven treatments

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Mulch Products in Experiment

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Treatment Company % Biobased Thickness (mil)

1. Bare ground2. Polyethylene (PE) FilmTech Corp. <1 13. BioAgri (Mater-Bi®) BioBag USA 20-25 0.7 4. Naturecycle Custom Bioplastics >20 1 5. Organix AG (ecovio®) Organix Ag. 10 0.7 6. Experimental PLA+PHA Experimental Film 86 1 7. WeedGuardPlus Sunshine Paper Co. 100 9.4

WeedGuardPlus is a cellulosic (paper) mulch

PLA: polylactic acid; PHA = polyhydroxyalkanoate;

BioAgri and Naturecycle consist of polyester/starch blends; Organix of polyesters

All mulches were 48 inches in width

Crop Data

• Mulch percent visual degradation (twice a month)• Weed counts (2 weeks after planting, mid-season, and late

season)• Insect and disease scouting• Yield (marketable/total, weights and numbers)• Storage & quality evaluation (every 2 wks for 8 wks)

– Weight loss - Color– Soluble solids - Dry weight

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Marketable Yield by Weight

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0

5

10

15

20

25

30M

arke

tabl

e Y

ield

(t/

ha)

Knoxville '15

Mount Vernon '15

Knoxville '16

Mount Vernon '16

a

a

abab

bcbca

d

bbb

bb

cd

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Potential for Mulch Adhesion

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Fruit with Mulch Adhesion

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Ghimire et al. HortScience 2018

Percent Soil Exposure

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Percent Soil Exposure

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Summary

• Several mulches performed similarly to black plastic• Yield was significantly different in Mt. Vernon, where

soil and air temperatures are cooler• Mulch adhesion unintended consequence with crops

that touch the ground• Breakdown varies by location, as well as weather in a

given season

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Pepper Trial

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Project Design

• Location: Knoxville, TN• ‘Aristotle’ bell pepper• 30 ft plots of 5 rows each, 7’ apart, replicated 4 times• Transplanted: 5/25/17 and 5/29/18• Double, staggered rows 12” apart,

18” within row spacing• Harvested weekly: 7/26/17-9/19/17

and 7/16/18-8/27/18• Eight treatments• Fertigated weekly during season

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Mulch Products in Experiment

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Treatment Company % Biobased

Thickness mil (µm)

1. Bare ground2. Polyethylene (PE) FilmTech Corp. <1 13. BioAgri (Mater-Bi®) BioBag USA 20-25 0.7 4. Naturecycle Custom Bioplastics >20 1 5. Organix AG (ecovio®) Organix Ag. 10 0.7 6. White-on-black (ecovio®) Organix Ag. 10 0.77. Experimental PLA+PHA Experimental Film 86 18. WeedGuardPlus Sunshine Paper Co. 100 9.4WeedGuardPlus is a cellulosic (paper) mulch

PLA: polylactic acid; PHA = polyhydroxyalkanoate;

BioAgri and Naturecycle consist of polyester/starch blends; Organix of polyesters

All mulches were 48 inches in width

Crop Data

• Mulch percent visual degradation (twice a month)• Weed counts (2 weeks after planting, mid-season,

and late season)• Plant health ratings, insect and disease scouting• Petiole sap nitrate sampled 5 times at key growth stages

(first flower buds, first open flowers, fruits 1/2-grown, 1st & 2nd

harvest)

• Quality evaluation- Color - Soluble solids

• Yield (marketable/total, weights and numbers)

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Percent Soil Exposure

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0

10

20

30

40

50

60

70

80

90

100

11 20 39 50 69 81 104 113

PSE

DAYS AFTER PLANTING

2017

0

10

20

30

40

50

60

70

80

90

100

4 17 36 49 67 78 95

PSE

DAYS AFTER PLANTING

2018

BioAgri

Exp. PLA/PHA

Naturecycle

Organix

Polyethylene

WeedGuardPlus

White‐on‐black

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Plant Health Ratings

a a

b

a

b

a

c

b

b

ab

a

a aa a

0

5

10

15

20

25

30

35

11-Jul 9-Aug

# h

ealt

hy p

lan

ts in

th

ird

row

(t

mt

avgs

)

2017

Number of healthy pepper plants in the data collection rows by a visual rating during the 2017 and 2018 pepper growing seasons in Knoxville, TN.

a a

b

b

a

b

bc

bc

bc

cdc

d

a

ab

a

ab

0

5

10

15

20

25

30

35

3-Jul 14-Aug2018

Bare ground

BioAgri

Exp. PLA/PHA

Naturecycle

Organix

Polyethylene

WeedGuardPlus

White-on-black

Healthy plants in WGP plot Stunted plants & NS pressure in PE plot

July 16, 2018

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Weed Control

• Know your weed community going in!• Nutsedge can be a BIG problem!• WeedGuardPlus excellent for controlling weeds during

critical period

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Number of Weeds (per m2)

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2017 19 June 19 July 6 SeptBare ground 88.5 a 34.1 a 38.9 abBioAgri 1.3 d 13.4 b 37.1 bExp PLA/PHA 17.3 bc 51.8 a 68.2 abNaturecycle 16.0 b 43.6 a 74.3 aOrganix 15.1 bc 58.3 a 84.2 aPE 3.0 bcd 34.1 a 63.0 abWeedGuardPlus 2.6 d 6.5 b 12.1 cWhite-on-black 3.5 cd 35.0 a 47.5 abP-Value <.0001 0.0019 0.0006

2018 13 June 18 July 21 AugBare ground 11.2 de 41.9 cd 15.5 cBioAgri 23.7 bcd 83.7 bc 165.3 aExp PLA/PHA 144.2 a 309.5 a 179.6 aNaturecycle 29.4 bc 161.9 ab 238.7 aOrganix 18.1 bcd 159.7 ab 172.7 aPE 14.7 cde 29.8 d 52.7 bWeedGuardPlus 1.7 e 15.5 d 16.8 cWhite-on-black 33.7 b 174.0 ab 162.3 aP-Value <.0001 <.0001 <.0001

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Pepper Yield

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Treatment Season total fruit yield by weight

2017 yield (tons/ha)

2018 yield (tons/ha)

% unmarketable 2017

% unmarketable 2018

Bare ground 35.8 ab 24.4 a 5.7 19.3BioAgri 37.9 a 8.7 bc 8.9 28.2Exp. PLA/PHA 27.7 ab 7.4 bc 10.5 30.3Naturecycle 17.3 c 8.7 bc 13.0 23.1Organix 26.8 bc 5.4 c 10.8 33.3Polyethylene 33.8 ab 1.3 c 11.9 50.0WeedGuardPlus 34.9 ab 22.1 a 9.7 31.6White-on-black 33.7 ab 15.7 ab 13.3 31.4P-value 0.0053 <.0001

Pepper Yield by Size Classes

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Treatment Marketable size classes - season total fruit (tons/ha)2017 2018

Small Medium Large Choppers Small Medium Large Choppers

Bare ground 8.02 ab 8.85 10.62 ab 5.07 ab 4.68 a 5.83 a 4.88 a 3.67 a

BioAgri 7.02 abc 8.36 12.29 a 3.94 bc 1.83 bc 1.57 bcd 1.38 bc 1.44 bc

Exp. PLA/PHA 5.52 bc 7.82 7.17 abc 2.64 cd 1.47 bc 1.38 bcd 0.98 bc 1.24 cd

Naturecycle 4.77 c 4.01 3.74 c 1.77 d 1.18 bc 2.15 bcd 1.76 bc 1.06 cd

Organix 6.14 bc 5.69 6.19 bc 3.98 b 0.92 bc 1.01 cd 1.03 bc 0.58 cd

Polyethylene 6.89 abc 7.07 9.21 ab 4.67 ab 0.24 c 0.14 d 0.04 c 0.23 d

WeedGuard 10.03 a 8.12 7.26 abc 5.25 ab 4.25 a 3.60 ab 3.59 ab 3.39 aW-o-B 7.19 abc 7.49 6.12 bc 7.53 a 2.61 ab 2.29 abc 2.44 ab 2.80 ab

P-value 0.0425 0.0622 0.0460 <.0001 0.0006 0.0027 0.0119 <.0001

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Summary

• Transplants established more quickly in WOB, paper and bare ground plots, likely due to excessive heat; all treatments equalized later in 2017, but not in 2018

• Lower seasonal total yields in PLA/PHA, Organix and Naturecycle due to nutsedge infestation in 2017

• Heat and nutsedge more severe in 2018 leading to reduced yields compared to 2017

• WOB had the highest % of unmarketable fruit in 2017; PE had the highest % of unmarketable fruit in 2018

• Paper degraded quickly, but was only treatment that prevented nutsedgeemergence and prevented weeds during critical period

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Sweet Corn Trial

Photo courtesy of Miles, 2019.

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Percent Soil Exposure

2017

0

20

40

60

80

100

10 24 41 56 71 85 99 115

DAYS AFTER SOWING

2018

0

20

40

60

80

100

8 22 38 52 70 84 100

PSE

DAYS AFTER SOWING

Slide courtesy of Miles, 2019.

Mulch deterioration

WGP

BioAgri PLA/PHA

Organix-Clear

Naturecycle

Organix-Black

PE

14 July 2017

‘Xtra-Tender 2171’ sweet corn

Slide courtesy of Miles, 2019.

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Sweet Corn Yield (t/ha)

Treatment 2017 2018

Polyethylene 12.1 a 19.8 a

Exp. PLA/PHA 10.0 abc 19.9 a

BioAgri 9.6 bc 17.1 b

Naturecycle 9.3 bc 19.8 a

Organix Black 10.2 abc 18.6 ab

Organix Clear 7.6 cd 17.6 b

WeedGuardPlus 5.6 d 13.9 c

Bare ground 6.5 d 13.7 cP-value 0.0003 <0.0001

Slide courtesy of Miles, 2019.

Conclusions

• BDMs have a bit of a handling learning curve• Several BDMs performed comparably to

polyethylene• Consider your weeds before choosing a

mulch• More work to be done!• Stay tuned…

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Acknowledgements

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, Ting Chi, Hayley Chouinard, Jeremy Cowan, Peter Tozer, Andy Bary, Lydia Tymon, Katie Dentzman, Jennifer Moore, Amy Salamone, Babette Gunderson, Ed Scheenstra, Jacky King, Marie English, Sreejata Bandopadhyay, Marife Anunciado, Shuresh Ghimire, Henry Sintim, Kuan Chen, Sarah Bellingham, Jose Liquet y Gonzalez

USDA SCRI Project No. 2014-51181-22382

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Thank you! Questions? annettew@utk.edu

For more information:www.biodegradablemulch.org