DEGRADABLE MULCH FOR AGRICULTURE:

YEAR 1 COMPREHENSIVE ANALYSIS OF A FIELD STUDYKaren K. Leonas1, Hang Liu1, Jeremy Cowan4, Douglas G. Hayes2, Larry C.Wadsworth2, Russell Wallace3, Carol Miles4, Annette Wszelaki2, Jeffery Martin2 andDebra Inglis4

1Washington State University, Pullman, WA, 2University of Tennessee, Knoxville, TN, 3Texas A&M University, Lubbock, TX, 4Washington State University, Mount Vernon, WA

SCRI-SREP Grant Award

No. 2009-02484

USDA Hatch Act: Multistate Regional Project – S 1026

Contact First Author at kleonas@wsu.edu; Contact Speaker at lwadswor@utk.edu

The Fiber Society Spring 2011 Conference, The Hong Kong Polytechnic University, Hong Kong, May 23-25, 2011

Biodegradable Mulches for Specialty Crops Produced

Under Protective CoversDebra Inglis and Carol Miles (Project Directors)1;

Curt Beus, Andrew Corbin, Ana Espinola-Arredondo, Karen Leonas, Tom Marsh and Tom Walters1;

Doug Hayes, Bobby Jones, Jaehoon Lee, Larry Wadsworth and Annette Wszelaki2;

Eric Belasco and Jennifer Moore-Kucera3;

Russ Wallace4; and, Marian Brodhagen5

1 2 34

5

SCRI-SREP Grant Award

No. 2009-02484

Introduction

Background

•Mulches as a row cover can provide:

�Conservation of soil moisture

�Modifies soil temperature

� Increases crop yield

�Shortens time to harvest

•Traditional mulches are:

�From non-renewable petroleum feed stocks

� In many regions non-recyclable

�Labor intensive to remove

�High disposal cost

� If not removed cause soil erosion

Biodegradable Mulches

• Investigation of Biodegradable Mulches (BDM)

• Life expectancy – preferably less than one year and non-accumulating in soil

• Till back into soil without negatively impacting soil ecosystem

- Need to maintain a healthy microflora/fauna with no release or accumulation of foreign or toxic substances

Biodegradable Mulches

• Reviews changes in tensile strength, elongation, and tearing strength of 5 mulches

– 3 marketed as biodegradable

– 1 non-biodegradable

– 1 experimental nonwoven from PLA fibers

• Analyzes Mn of 3 mulches up to 20 weeks

• Year 1 of a 3 Year study

This presentation

Methods and Materials

A tomato cultivar plot in TN

Experimental Design

• 5 Mulches � Biobag �BioTelo �Spunbond PLA� Non-biodegradable PE �Cellulosic

• Locations�WA �TN �TX

• Evaluation Times� Control �Field control �First flower �Final harvest

• Environments� Inside high tunnel �Open field

5 mulches x 4 times x 3 locations x 2 environments x 4 replications

General Protocol

• Mulch samples cut from predetermined locations, which were not covered with soil in row, cleaned & sent for testing (WSU Pullman)

• If necessary, additional cleaning was completed in Pullman

• In a separate study, specimens of each mulch have been put into nylon open mesh bags along with soil and buried in same plots without mulch cover and analyzed at different times for up to two years for degradation

Laying mulch (WA) Cutting SB (WA) Transplanting vegetables (WA)

PLA

Cellulose

Polyethylene

(non-biodegradable)

(C6H10O5)n

Corn Starch (BioBag, BioTelo)& Non-disclosed Biopolymer(s)

Chemical Structures of MulchesChemical Structures of Mulches

Mulches

SCRI Project Locations

WSU Mount Vernon

TA&M Lubbock

UT Knoxville

WSU Pullman –

Materials Testing

& Materials Analysis

Sampling Time Dates

Time 1 - Mulch Laid

Time 2 - First FlowerTime 3 - Final Harvest

Environment

In High Tunnel Open Field

Testing:

Physical properties measured to evaluate degradation

&

Property Test Method Test equipment

ThicknessASTM D5729-97 Test method for thickness of textile materials

(10 specimens)

Digital Micrometer M121 (Testing

Machines Inc.) (test range: 0.01mm ~

20mm)

WeightASTM D3776-07 Test method for mass per unit area (weight)

of fabric (5 specimens)

Balance ( BC 100) (test range: 0.001g ~

210g)

Stiffness

IST 90.2 (01) Standard test method for stiffness of nonwoven

fabrics using the Gurley Tester (5 specimens for each fabric

direction)

Bending Resistance Tester (Gurley

Precision Instrument) (test range: 2.78mg

~ 335328mg)

Tearing strength

ASTM D5734-95(2001) Test method for tearing strength of

nonwoven fabrics for by falling-pendulum (Elmendorf)

apparatus (5 specimens for each fabric direction)

Digital Elmendorf Tearing Tester (Tonny

International Co. LTD) (test range: 160cN

~ 3840cN)

Tensile properties

ASTM D5035-06 Test method for breaking strength and

elongation of textile fabrics (Strip method) (5 specimens for

machine direction and 8 specimens for cross direction)

Instron 5565A (Instron Corporation) (test

range: 0.4N ~ 5000N)

PorosityNo standard test method applies. (Ten specimens were tested

following the equipment instruction manual)

Capillary Flow Porometer CFP-1200AEX

(Porous Materials, Inc.) (test range:

0.013µm ~ 500µm)trR

Resistance to

weathering

ASTM G155-05a Standard practice for operating xenon arc

light apparatus for exposure of non-metallic materialsAtlas Ci 3000+ Xezon Weather-ometer

Molecular Weight &

Polydispiserty

No standard test method applies. (Three specimens per

sample were tested)Gel Permeation Chorography

Biodegradation

In soil

ASTM D 5988 Test method for determining aerobic

biodegradation in soil of plastic materials or residual plastic

materials after composting

As specified in test method

Test methods to measure mulch properties

Sampling Plan for Laboratory Testing

Tensile/elongation

Tearing Strength

Flexibility

Porosity

Results and Conclusions

Photos:

Mulch after exposure

Micrographs :

Time 0 & Time 3

Properties Reported:

Maximum load (machine direction)

Maximum elongation(machine direction)

Molecular Weight

Influence of:

Location

Environment

Time

Tensile PropertiesTime 0 – Maximum Load – Machine direction

Time 0 – Maximum Load – Machine direction

Time 0 - % Elongation – Machine Direction

Year 1 Tearing Strength Graphs – Machine Direction

Time 0 Tearing Strength (g)

Time 0/1 Time 2 Time 3

TN

TX

WA

BioBag

Time 0/1 Time 2 Time 3

TN

TX

WA

BioTelo

Time 0/1 Time 2 Time 3

TN

TX

WA

Non-biodegradable

Time 0/1 Time 2 Time 3

TN

TX

WA

Cellulosic

Time 0/1 Time 2 Time 3

TN

TX

WA

SB PLA

Time 0 Time 3

(HT – TX)BioTelo

Magnification 20000x

Time 0 Time 3

(FD – TX)

Non-biodegradable

Magnification 1000x

Time 0 Time 3

(FD – WA)

Cellulose

Magnification 500x

Time 0 Time 3

(HT – WA)

SB PLA

Magnification 100x

Time 0 Time 3

(FD – WA)

SB PLA

Magnification 2000x

Time/Location/EnvironmentPercent Maximum Load

Time/Location/EnvironmentPercent Maximum Elongation

Time 0 Time 3

(FD – HT)

BioBag

Magnification 20000x

Comparison of Locations/Environment

Percent of Maximum Load at Time 3

Open Field High Tunnel

Time 3 – Field - % Elongation – Machine Direction

- Comparison of Locations/Environment

Time 3 – HT - % Elongation – Machine Direction

- Comparison of Locations/Environment

Time 3 – Field - Tearing Strength – Machine Direction

– Comparison of Locations/Environmen

Time 3 – HT - Tearing Strength – Machine Direction

– Comparison of Locations/Environmen

Time 3 Tearing Strength – Machine Direction – Comparison of FD & HT

Spunbond PLA

BioTelo

BioBag

Conclusions

• Loss of strength & elongation influenced by mulch treatment

• Environment (Field vs High Tunnel)

� In general, reduction in elongation was greater for those products in the field environment compared with the high tunnel by end of exposure (Time 3).–Cellulose & SB PLA – greater reduction in Field for all locations

�However, reduction in tensile strength varied based on mulch and location–Cellulose & SB PLA – greater reduction in Field for all locations

Conclusions – con’t

• Location (WA vs TN vs TX)

� Based on current analysis, one location did not consistently result in the greatest property loss

•Time

� In all cases, regardless of mulch/location/ environment –Tensile and tearing strength and elongation values decreased during exposure

Conclusions – con’t

•Molecular Weight

�Mn of SB PLA in HT and FD appeared to decrease slightly with time in all three locations

�With BioBag, Mn decreased with time in all environments. After T3, TX HT and TN HT showed the largest decrease, followed by TN field, WA HT and WA field

�With BioTelo, Mn also decreased with time in all three environments. After T3, the largest decrease occurred with TN HT and TX FD, followed by TN FD, WA HT, WA FD and TX HT

Future Work•Completion of Year 1 of 3 Year Study

• Based on results to date,

�modifications are being made to the PLA Mulch to be used in Year 2 and in Year 3

� Evaluation of tests that best predict degradation

•Analysis of samples buried in soil in nylon mesh bags for degradation

• Laboratory accelerated weathering and other conditions of exposure (sunlight, temperature, relative humidity, and soil moisture content) will be studied