Plastic Mulches

Introduction

Polyethylene (PE) mulch has been used as a tool in agriculture since the 1950s to improve weed management, reduce soil water loss, raise soil temperature, increase yield, improve crop quality, and shorten harvest time. U.S. agriculture uses about 1 billion pounds of plastics annually. Recycling of agricultural plastic is not available in many regions, so many growers dispose of their plastic waste in a landfill or stockpile on their farms. Soil-biodegradable mulch (BDM; paper or plastic) has been developed as an environmentally friendly alternative to PE mulch. At WSU, we are testing BDMs to find effective and affordable alternatives to PE mulch to reduce non-recyclable waste. We have also been partnering and collaborating with other universities and enterprises to find solutions to improved end-of-life management of agricultural plastics in specialty crop systems.

Biodegradable plastic feedstocks are biobased, derived from fossil fuels, or a blend of the two. The most common biobased feedstocks used to make biodegradable plastic mulches are starch, polylactic acid (PLA), and polyhydroxyalkanoates (PHA). Paper mulch is completely biobased and made from cellulose (WeedGuardPlus^® is an example of a paper mulch). Climate (temperature, moisture, solar radiation, wind, etc.) and soil conditions affect the extent and rate of biodegradation of BDMs, however, it also largely depends on the feedstocks used in the product formulation and material thickness.

Our BDM research began in 2003 when we started working with companies to field test their BDMs. Our collaborative research projects include:

• Application of polyethylene (PE) mulch and BDMs in tissue culture red raspberry
• Use of BDMs in strawberry
• Tomato yield and fruit quality using BDMs in open fields and high tunnels
• Impact of BDMs on pie pumpkin yield and fruit quality
• Broccoli production with BDMs
• Growth, yield, and quality of sweet corn grown with BDMs

In addition to our BDM work, we are also exploring new applications of non-degradable plastic mulches and improved end-of-life management strategies to reduce mulch waste.