Biodegradable Mulch Films for Weed Suppression in the Establishment Year of Matted-row Strawberries

Adequate weed control in the establishment year of matted-row strawberries (Fragaria ×ananassa) is crucial for the long-term viability of plantings. Suppression of weed growth until the new strawberry plants are established and runners rooted is an effective strategy in new plantings. Three biodegradable mulch films were compared to standard weed control for establishing matted-row strawberries. Two films were test products using a biodegradable polymer, either clear or black, covering brown 40-lb kraft paper (IP40 Clear and IP40 Black, respectively). The third material was Planters paper, a black paper mulch. The films were evaluated for weed suppression, rate of degradation and effects on runner production and fruit yield. Additionally, the ability of runners that were formed to root as the film degraded was also observed. The IP40 Black mulch reduced the number of weeds compared to the standard control but did not degrade quickly enough for runners to root. The Planters paper also had fewer weeds, but it degraded quickly along the edges where it was covered by soil. This allowed the wind to tear it and blow large pieces off the plots. The IP40 Clear degraded in a timely manner and allowed runner rooting, but it was not acceptable as a weed suppression material. The IP40 Black and Planters paper mulches were effective for weed control in the establishment year, but rate of degradation was too slow in the former case and too fast in the latter. Runner production and fruit yield were not affected by any of the mulch materials compared to standard control. Weed control is the most pressing problem encountered by strawberry growers using a matted-row strawberry production system. Newly planted strawberries in the matted-row system are most susceptible to weed competition during the fi rst 2 months after planting. Yield losses of up to 65% have been documented when early season weed competition was not controlled (Pritts and Kelley, 2001). Weed control during this period is especially critical for the long-term viability of new plantings and is diffi cult because only a few herbicides with limited residual activity are available for establishment year weed control (Pritts and Kelley, 2001). Thus, using herbicides alone is not effective for preventing weed competition in the establishment year and yield reduction in future seasons. In a matted-row system, plants are planted from 12 inches (30.5 cm) to 24 inches (61.0 cm) apart in the row and runners from the transplants fi ll in the remainder of the row space. Row spacing varies from 42 to 52 inches (106.7 to 132.1 cm) from center to center (Pritts and Handley, 1988). Wheat (Triticum aestivum), rye (Secale cereale), or barley (Hordeum vulgare) straw is applied on established fi elds in the late fall of each year for winter cold protection and weed control in the following year. However, new plantings are without straw mulch for weed control until the second season. Weed competition within the rows can inhibit stand establishment and reduce future yields. Current plasticulture with non-degradable plastic mulch provides excellent weed control but cannot be used for establishing a matted-row planting because the plastic mulch stops runners from rooting and fi lling in the row. By using a material that degrades within 60 to 90 d of application, weed suppression during the critical part of the season could be accomplished while still allowing runners to fi ll in the row as the material degrades. The subsequent straw application in early winter would further aid in the degradation process and prevent blowing of mulch fragments thus making complete degradation more likely. Photodegradable and biodegradable mulches made of plastic, paper, or other materials have been tested for their utility for annual food production with varying degrees of success (Greer and Dole, 2003). As early as the 1920s researchers developed acceptable pro1Assistant professor, Department of Horticultural Sciences, New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456; e-mail caw34@nysaes.cornell. edu.