2017 ASHS Annual Conference

Plastic mulch is ubiquitous in the production of high value vegetable and small fruit crops; however, disposing of plastic mulch at the end of the season poses both environmental and economic challenges. Biodegradable mulch that could reduce weed pressure, moderate soil temperature, conserve moisture, and improve crop yield similarly to plastic mulch, yet fully biodegrade in the field at the end of the season after tillage incorporation with no negative impact to the soil, would benefit agriculture and the environment. Field experiments in 2015 and 2016 compared four potentially biodegradable mulches (BioAgri^®, Exp PLA/PHA, Organix, and Naturecycle), a cellulose mulch [WeedGuardPlus (100% biodegradable)], PE (polyethylene, non-biodegradable) and a bare ground treatment for their effect on pumpkin (Cucurbita pepo cv. Cinnamon Girl) fruit yield at two locations in the U.S. with distinctly different climates: Mount Vernon, WA and Knoxville, TN. Weed pressure was minimal in all mulch treatments at both locations both years because the mulches remained sufficiently intact until the end of the growing season, with the exception of Naturecycle in 2015 at both locations due to a splitting of the mulch. There was significant weed pressure in the bare ground plots at both locations both years, indicating the mulches provided a barrier to weed seed emergence and/or growth. Moreover, in Knoxville, nutsedge penetrated all of the mulches except the cellulose mulch. At Mount Vernon, overall pumpkin yield was 18.1 t^.ha^-1, and pumpkin yield was greatest with PE, Exp. PLA/PHA, BioAgri and Naturecycle (19.9 t^.ha^-1 – 22.8 t^.ha^-1), intermediate with Organix and WeedGuardPlus (15.3 t^.ha^-1 - 18.4 t^.ha^-1), and lowest for bare ground (8.7 t^.ha^-1). At Knoxville, overall pumpkin yield was 17.7 t^.ha^-1, and pumpkin yield did not differ due to treatment. The difference in yield at Mount Vernon was likely due to the difference in the soil temperature, which tended to be 1-2 ^°C lower for bare ground and WeedGuardPlus as compared to PE and biodegradable plastic mulches (19.1 – 23.3 ^°C). In contrast, at Knoxville soil temperature was higher in general for all treatments (25.3 – 28.3 ^°C). These results indicate that yield of pumpkin grown with biodegradable mulch are comparable with PE mulch at diverse locations.