J. Cowan, C. Miles 1, D. Inglis, K. Leonas, J. Moore-Kucera, A. Wszelaki, R. Wallace, D. Hayes, H. Liu, and L. Wadsworth 1 Department 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 Walters 1 ; Doug Hayes, Bobby Jones, Jaehoon Lee, Larry Wadsworth and Annette Wszelaki 2 ; Eric Belasco and Jennifer Moore-Kucera 3 ; Russ Wallace 4 ; and, Marian Brodhagen SCRI-SREP Grant Award No

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

* *

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), D and ASTM D6400

PropertiesTest MethodTest equipment Thickness ASTM D Test method for thickness of textile materials (10 specimens) Digital Micrometer M121 (Testing Machines Inc.) (test range: 0.01mm ~ 20mm) Weight ASTM D 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 ~ mg) Tearing strength ASTM D (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 D 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 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 mulchSB 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