Evaluating Potentially Biodegradable Mulches for Vegetable High Tunnel and Field Production

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Evaluating Potentially Biodegradable Mulches for
Vegetable High Tunnel and Field Production

• J. 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

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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
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SCRI-SREP Grant Award No. 2009-02484
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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

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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
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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

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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

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Table 1. Test methods and test equipment used to
measure BDM properties.
Properties Test Method Test equipment
Thickness ASTM D5729-97 Test method for thickness of textile materials (10 specimens) Digital Micrometer M121 (Testing Machines Inc.) (test range 0.01mm 20mm)
Weight ASTM 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)
Porosity No 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
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SEM photo TX at Time 2 (first flower)
non-biodegradable (PE) mulch
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cellulose mulch
SB PLA mulch
BioAgri mulch
BioTelo mulch
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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.

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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

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

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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,
  ß-carotene, and ascorbic acid

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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

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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