Evaluating Potentially Evaluating Potentially Biodegradable Mulches Biodegradable Mulches

for Vegetable High for Vegetable High Tunnel and Field Tunnel and Field

ProductionProductionJ. Cowan, C. Miles1, D. Inglis, K. Leonas, J. Moore-Kucera, A.

Wszelaki, R. Wallace, D. Hayes, H. Liu, and L. Wadsworth

1Department of Horticulture and Landscape Architecture, Washington State University, Mount Vernon Northwestern

Washington Research and Extension Center

Biodegradable Mulches for Specialty Crops Produced Under Protective Covers

Debra 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

Project Overview

Evaluating potentially biodegradable mulches (BDMs) and their effects on crop production and soil quality

Four potentially-biodegradable mulches under evaluation include 2 commercially available films and 1 cellulose mulch, and 1 experimental non-woven fabric

Field trials underway in Northwest WA, Eastern TN, and the panhandle of TX

Background High tunnels – earlier and higher yield, greater crop quality

Tomato – primary crop grown in HTs in the United States

Most HT systems utilize plastic mulch

Mulch – weed control and soil moisture conservation

A BDM could reduce the overall environmental impact of mulch

BDMs must perform under diverse environments:• Mount Vernon, WA – marine climate; cool summer, moderate precipitation;

soils loamy sand & high organic matter • Knoxville, TN – humid subtropical climate; mild winter; warm, humid

summer; soils heavy clay, low organic matter• Lubbock, TX – Southern High Plains region; hot summer; low humidity &

rainfall; high wind; soils sandy loam, low organic matter

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Mount Vernon, Washington field site, July 23, 2010

Experimental Design RCB with 4 replications of HT and open field plots at 3 sites

(WA, TX, TN)

6 treatments: • Experimental fabric – 100% spun-bond non-woven PLA• BioAgri – starch-based film• BioTelo – starch-based (Mater-bi®) film• Standard black plastic – PE mulch 1.0 mil embossed• Sunshine paper – cellulose• Bare ground / non-mulch control

Mulches hand laid in 3 ft beds, plots 6 ft wide & 14 ft long

Tomato cv. Celebrity – pruned, staked, managed organically

Drip irrigated

Assess Mulch (Bio)Degradation BDMs analyzed upon receipt (Time 0), mulch laying (Time 1), first

flower (Time 2), and final harvest (Time 3)

Visual assessments in the field twice per month

Evaluate primary physical/structural characteristics: measure thickness, weight, pore size, flexibility, tensile strength, elongation, and tearing strength

Mesh bag study post-harvest to observe in situ degradation and measure soil quality effects

Additional samples assessed using simulated weathering

Promising treatments evaluated for complete biodegradation under anaerobic and composting conditions per ASTM D5338 (2003), D5988-03 and ASTM D6400

Properties 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)

StiffnessIST 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)

Weathering resistance

ASTM G155-05a Standard practice for operating xenon arc light apparatus for exposure of non-metallic materials

Atlas Ci 3000+ Xezon Weather-ometer

Table 1. Test methods and test equipment used to measure BDM properties.

non-biodegradable (PE) mulch

SEM photo TX at Time 2 (first flower)

cellulose mulch SB PLA mulch

BioAgri mulch BioTelo mulch

Soil Assessments Soil sampled 0-15 cm prior to BDM treatments for

baseline soil quality information.

Mesh bag study – soil chemical and biological properties measured twice each year Chemical properties: pH, EC, CEC, total C and N Biological properties: microbial biomass C and N, N

mineralization potential, biological activity, and microbial community structure

Microorganisms capable of utilizing BDMs as sole C source will be cultured and identified.

Weed Assays Weeds collected, sorted, counted, and

weighed as BDMs are sampled

Non-mulch plots maintained weed-free

Mulches must suppress weeds: BDM durability and ability to block light to prevent weed germination is of key importance

SB PLA experimental mulch (white) and cellulose mulch (paper) plots

Plant Disease and Insect Assays

Weekly monitoring for foliar & root diseases, and insect activity

Weekly disease ratings converted to AUDPC values to compare potential epidemics

Insects monitored for crop damage, differential attraction to BDM treatments, and for control

Tomato fruits and plants rated for fruit, crown, and root diseases, and root mass/weight

Root health assessments – general plant pathology diagnostic and culture-based techniques, including plant imaging technology (Assess 2.0; APS, Minneapolis, MN)

Assess Crop Yield & Fruit Quality

Marketable fruit (USDA grading) for fresh market: weight and number for each grade

Unmarketable fruit categorized by disorder or disease (ie., cat facing, cracking, late blight, etc.)

Fruit quality assessments: juice content, soluble solids (Brix), pH, titratable acidity, lycopene, β-carotene, and ascorbic acid

Current Status BDM HT field studies underway in

Western WA, Central TX, Eastern TN

Baseline soil samples collected and analyzed

Time 0 & 1 mulch samples evaluated; Time 2 collected

Crop disease, insect, environmental, and yield data underway at all three locations

Expected Outcomes Appropriate assessments of mulch

degradation and biodegradation

Tomato, lettuce and strawberry cultivar selection for western WA, eastern TN and central TX

Crop disease and insect management recommendations for WA, TN and TX

HT management in windy environments

Understanding changes in soil chemical and biological variables due to BDM soil incorporation

Development of new SB non-woven BDM