Mount Vernon Northwestern Washington Research and Extension Center

Vegetable Research and Extension

Photo collage of watermelon tasting, tractor, dry beans

Biodegradable Mulch

Introduction

Since its introduction in the 1950s, black plastic (polyethylene plastic) mulch has been the primary tool used to reduce weed competition in both high tunnels and open fields, control water loss, raise soil temperature, increase plant production, and shorten harvest time. Weed control is one of the primary concerns in organic farming as it is labor intensive, expensive and time consuming. Though very effective and affordable, plastic mulch has become an environmental management concern due to disposal issues. In 1999, almost 30 million acres worldwide were covered with plastic mulch and more than 185,000 of those acres were in the United States. Essentially all of this plastic entered the waste stream. Recently, agricultural plastic recycling has begun, however, the disposal option that most growers choose is the landfill. A number of degradable mulch films have been developed that may work as environmentally-friendly alternatives to plastic mulch. At WSU, we are testing such products in order to find effective, affordable, degradable alternatives to standard plastic mulch which would contribute the same production benefits and reduce non-recyclable and non-renewable waste.

Plastic Mulch

Photo of lettuce grown through holes in biodegradable mulch
Lettuce grown on a plastic-covered raised bed, ready for harvest

Plastic mulch is commonly used to control weeds in the crop row, moderate soil temperature and conserve water in the plant root zone. There are many different colors and qualities of plastic mulch, and use varies depending on the season and crop being grown. There are also degradable mulches made of cornstarch and paper, and plastic mulches that are heat and/or light degradable.

Dimensions and costs of plastic and biodegradable mulch. Provides a summary of the size of plastic and biodegradable mulch rolls, the amount of mulch needed per acre, and the number of rolls needed per acre based on commonly used bed spacings and roll length.

Effects of Mulch Color. Color of mulch for eight different vegetable crops. The Pennsylvania State University.

Plastic Mulch Overview of what mulch is and a comparison of common types of mulch. Also, links to further information on mulches. The Pennsylvania State University.

Plastic Mulch & Drip Irrigation. Includes detailed instructions for drip irrigation set-up, rates of irrigation, fertigation methods and quantities, double cropping suggestions, and cost estimates for a plastic mulch system. North Carolina State University Extension.

Use of Plastic Mulch. Outline of advantages and disadvantages of using plastic mulch, and detailed instructions on plastic mulch application, planting, maintenance, and removal. Oklahoma State University Extension.

Biodegradable Mulch

Photos of transplanting tomatoes in biodegradable mulch test plots under high tunnel
Transplanting tomatoes in biodegradable mulch test plots under high tunnel

Biodegradable mulches are manufactured alternatives to plastic mulch and, ideally, provide the same benefits as plastic mulch (weed control, soil temperature moderation, soil moisture retention, and soil conservation). They also offer the added benefit of being 100% biodegradable, either in the field, soil or in composting, with no formation of toxic residues.

Biodegradable Alternative to Plastic. Vegetable oil coated paper mulch as an alternative to plastic mulch. USDA ARS.

Biodegradable mulch field research project. A short video highlighting a field research project at Washington State University, from laying biodegradable mulch in the field, to pumpkin growth, to harvest and fruit storage.

Biodegradable Mulch Film for Organic Production Systems. WSU Mount Vernon NWREC Report 102, C. Miles and E. Scheenstra.

Biodegradable Polymers. Provides classification and chemical structures for biodegradable polymers. University of Strasbourg, France.

Degradable Mulch. Research study testing various degradable mulch products in vegetable crops. Washington State University Extension.

Dimensions and costs of plastic and biodegradable mulch. Provides a summary of the size of plastic and biodegradable mulch rolls, the amount of mulch needed per acre, and the number of rolls needed per acre based on commonly used bed spacings and roll length.

Mechanically laying biodegradable paper and plastic mulch. Laying biodegradable mulch by machine is not difficult when appropriate steps are taken to reduce the tension of the mulch layer wheels. This factsheet provides an overview of how to accomplish this.

Misleading Claims and Misuse of Standards Proliferate in the Nascent Bioplastics Industry Space. Narayan, R. 2010. Bioplastics Magazine, Polymedia Publisher GmbH. 10(1):38-41.

Sorting Through Facts and Claims. Narayan, R. 2010. Bioplastics Magazine, Polymedia Publisher GmbH. 10(1):29-31.

Presentations

Paper mulch, part of the series Weed 'Em and Reap. Produced by Oregon State University. Carol Miles, Martin Nicholson, and Lydia Garth, Washington State University. Vancouver WA

Research Reports

2007 Research Trial. This study included 8 degradable mulches: Garden Biofilm, Garden Biofilm NF01U/P 15 mic, Garden Biofilm NF803/P 12 mic, Garden Biofilm NF803/P 15 mic, Longview Fibre Paper (LF) 4, LF 5, LF 5 Black, Planters Paper, and black plastic (control). The study was conducted in the field at the Washington State University Research and Extension Unit in Vancouver, Washington and included four vegetable crops: lettuce, broccoli, green peppers and watermelon.

2006 Research Trial. This study included 9 degradable mulches: Garden Biofilm, Garden Biofilm NF01U/P 15 mic, Garden Biofilm NF803/P 12 mic, Garden Biofilm NF803/P 15 mic, Envirocare 1, Envirocare 2, Longview Fibre Paper (LF) 4, LF 5, Planters Paper and black plastic (control). The study was conducted in the field at the Washington State University Research and Extension Unit in Vancouver, Washington and included four vegetable crops: lettuce, broccoli, green peppers and watermelon.

2005 Research Trial. This study included eight degradable mulches: Garden Biofilm, Envirocare 1, Envirocare 2, Longview Fibre Paper (LF) 1, LF 2, LF 3, LF 4, Planters Paper and black plastic (control). The study was conducted in the field at the Washington State University Research and Extension Unit in Vancouver, Washington and included four vegetable crops: lettuce, broccoli, green peppers and watermelon.

2004 Research Trial. This study included five degradable mulches and black plastic: 81-lb Kraft brown paper, 42-lb Kraft brown paper with polyethylene coating, Garden BioFilm, Envirocare 1 (XP-4611W), Envirocare 2 (XP-4611J), black plastic (control).

2003 Research Trial. This study included six mulch treatments: Garden Bio-Film, 81-lb Kraft paper, Kraft paper + linseed oil, Kraft paper + tung oil, Kraft paper + soybean oil, and black plastic (control). Oil was sprayed onto the paper prior to laying the paper in the field, and its purpose was to reduce the rate of paper degradation in the field.

 

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