Adhesion of Biodegradable Mulches to Pie Pumpkins: A Production and Quality Consideration

Plastic mulches provide many advantages for specialty crop production, however, disadvantages include the cost, labor and environmental issues associated with plastic mulch disposal. Although biodegradable mulches (BDMs) potentially offer an alternative to traditional plastic mulches, BDMs will only be a sustainable technology and widely adopted if they cause no harm to the environment, reduce landfill waste, and reduce overall labor costs- especially those for removal and disposal- all while providing benefits comparable to polyethylene mulch. BDMs are designed to cover the soil during the production season, and then begin to degrade as harvest nears. A consequence of degradation is that mulch pieces can adhere to the bottom of fruit resting on the BDM. Leaving adhered mulch on the fruit renders it unmarketable, but removing it adds extra labor costs, and growers are not likely to invest their resources in cleaning mulch from their crops. In this study, we grew pie pumpkins (Cucurbita pepo), cv. Cinnamon Girl, on five BDM treatments (BioAgri, Metabolix, Naturecycle, Organix and WeedGuardPlus) and a black plastic mulch control on raised beds in two distinct regions of the U.S.- the cool, humid Pacific Northwest in Mount Vernon, WA (15 ^oC average daily temperature and 83% average relative humidity) and the hot, humid Southeast in Knoxville, TN (22 ^oC average daily temperature and 73% average relative humidity). We counted pumpkins with mulch adhesion at harvest as one component of fruit quality; included in the count at Mount Vernon were the total number of fruit with adhered mulch (marketable plus unmarketable), and at Knoxville the count included fruit with adhered mulch that would have otherwise been marketable (marketable only). In Mount Vernon, all BDM treatments except Metabolix (1% mulch adhesion) had considerable mulch adhesion (30-50%). In Knoxville, Organix had 19% of otherwise marketable fruit with mulch adhesion, more than any other treatment except BioAgri with 10%. Observations in the field indicate that adhered mulch could be wiped off fruit in the early morning when fruit was damp from morning dew, yet as temperature increased throughout the day and the mulch dried on the fruit, it was no longer possible to easily remove the adhered mulch. In 2016 this study will be repeated and both sites will count and weigh fruit into categories of marketable, unmarketable, and fruit with adhered mulch (that would have been marketable otherwise).