Carol Miles, Kathryn Kolker, Jenn Reed and Gail Becker
WSU Vancouver Research & Extension Unit
1919 NE 78th Street, Vancouver, WA 98665

Abstract. Plastic mulch is a standard practice used by farmers to control weeds, conserve moisture, and shorten time to harvest. An effective, affordable, degradable alternative to plastic mulch would contribute the same production benefits and in addition would reduce non-recyclable waste. Ideally, farmers would like to plow down the mulch at the end of the season, thereby eliminating removal as well as disposal costs. At Washington State University we conducted a preliminary summer field trial in 2004 and a replicated summer field trial in 2005 and 2006 to evaluate degradable plastic (Envirocare, TDPATM), paper and cornstarch mulches as alternatives to plastic mulch. Field trials included four different vegetable crops (lettuce, broccoli, bell pepper, and icebox watermelon), each with a different time to maturity and optimum temperature regime. Preliminary results from this study showed that both Envirocare mulches were as durable as black plastic; quality of these products declined only slightly over the course of the growing season. Different paper and cornstarch mulches exhibited different qualities over the season, but all were significantly less durable than black plastic. Mulch products significantly affected vegetable crop yields each year. Yields in all paper plots were significantly lower due to the general degradation of the mulch products and the subsequent weed growth in those plots. Yield of lettuce was least impacted by mulch product due to its short time to harvest, and paper or cornstarch products may be most suitable for similar short season crops.

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