Effect of weathering on biodegradability of biodegradable mulch film
Anunciado, M., L. C. Wadsworth, D. B. Cowan-Banker, and D. G. Hayes.  2017.  BioEnvironmental Polymer Society 24th Annual Meeting, Albany, CA, 20-22 September 2017 (poster).

Abstract:
Plastic mulches are employed widely in agricultural production of vegetables and other specialty crops due to their numerous benefits in promoting increased crop yield and overall good quality production through limiting soil water evaporation, inhibiting weed growth and maintaining soil temperature conducive for root growth. Disposal after consumer use, however, is still a pressing issue, since conventional polyethylene (PE) mulches do not have desirable end-of-life options: poorly biodegradable and recyclable. Residual PE mulch fragments may cause harm to water and soil-related ecosystems. Biodegradable mulches are potentially useful replacements for PE mulches due to their ability to be tilled into the soil after crop harvest; however, the long-term impacts of using biodegradable mulches for specialty crop production is unknown. This research study evaluates the effect of two diverse climates on the weather-induced degradation of mulch films used and applied to two research stations located in Knoxville, Tennessee (East Tennessee Research and Education Center, ETREC) and in Mount Vernon, Washington (Northwestern Washington Research and Extension Center, NWREC) in 2015, and compared to artificial weathering. Mulch treatments consisted of three commercially available mulches consisting mainly of polybutylene co-adipate co-terephthalate (PBAT) and an experimental film prepared from a polylactic acid/polyhydroxybutyrate blend, with PE and paper mulch serving as controls. Changes on the physical and chemical properties of BDM films were compared between the two locations. Biodegradability of agriculturally-weathered and unweathered mulches under two laboratory-controlled conditions: 1) composting and 2) in-soil conditions using ASTM-D5338 and ASTM-D5998, respectively, were also evaluated. Results showed that BDM films from ETREC showed major and most changes on physicochemical properties than NWREC which are attributed to variability of weather conditions. Among measured environmental parameters, the higher precipitation and temperature observed in Tennessee induced depolymerization, given that the solar radiation among the weathering treatments in 2015 were similar. Higher CO2 evolution was observed for agriculturally-weathered mulches compared to unweathered mulches, reflecting the increased exposure of mulch surface area to soil due to the embrittlement of the former.