2018 ASHS Annual Conference

Plastic mulch has many benefits (e.g. weed and disease management, increased yield and quality, moisture conservation), but also several drawbacks (e.g. disposal cost, environmental concerns). Biodegradable plastic mulches (BDMs) offer a potential alternative if they can provide similar advantages to polyethylene plastic mulch without the disadvantages of additional labor costs for removal and disposal, contributing to landfill waste and polluting the environment. In a field experiment in 2017, we tested five potentially biodegradable plastic mulches (Experimental PLA/PHA, Organix A.G.: Black, Organix A.G.: White-on-black (WOB), Naturecycle and BioAgri), a creped cellulose mulch (WeedGuardPlus), polyethylene plastic mulch (non-biodegradable) and a no-mulch treatment for their effects on pepper (cv. Aristotle) petiole sap nitrate status, and fruit yield and quality. Additionally, weed assessments were conducted three times during the season (early, mid and late-season), and mulch degradation or percent soil exposure (PSE)- a visual rating of the amount of soil exposed due to mulch degradation- was measured twice monthly over the growing season. Petiole sap nitrate was lower in the white-on-black and paper mulches and bare ground plots at first flower and second harvest (range of 205-281 NO₃N ppm for bare ground, paper and WOB, range of 577-775 NO₃N ppm for the black mulches at first flower). Total season yields for marketable number of fruit per plot ranged from 35.4 to 38.5 in bare ground, BioAgri, PE, WeedGuardPlus and WOB, but were lower in Exp. PLA/PHA, Naturecycle and Organix (27, 18.2, and 27.1 respectively), likely due to severe nutsedge pressure. Nutsedge penetrated all of the mulches, except WeedGuardPlus. The number of weeds per m² at the late season weed rating was only 12.1 for WeedGuardPlus and ranged from 37.1-84.2 for all other treatments. The quality parameters of color and soluble solids did not differ among mulch treatments. The paper mulch degraded more quickly than the other mulches and very little, if any, of the mulch could be seen by the end of the season (PSE 100% for WeedGuardPlus, other treatments ranged from PSE of 15% for PE up to 69% for Naturecycle). In spite of this degradation, WeedGuardPlus generally stays intact during the critical weed period (first 4-6 weeks after planting) until the plant canopy fills in, providing nearly season long weed control. With this in mind, it is important to consider the most important benefits to be gained from the BDM before choosing a product.