2018 ASHS Annual Conference

Polylactic acid (PLA) based agricultural mulches provide several benefits including environmental sustainability, durability, weed control, and soil moisture conservation. Despite these potential benefits, large-scale adoption of PLA mulches in organic and conventional agricultural systems has been hampered by unpredictable biodegradation and persistence in soil. A 16-week microcosm study was implemented to assess the effects of four commercially available biostimulants including Biocat 1000, Extract PBA, Custom GP, and Environoc 501, a compost extract, and distilled water, urea, and sucrose controls on biodegradation and microbial respiration of bio-based agricultural mulches in native soil. Mulches included PLA biofabric, two novel composite PLA biofabrics with embedded alfalfa (PLA-A) and soy (PLA-S) particles, paper mulch (PA), and bioplastic film (BF). After 16 weeks, the PLA-A and PLA-S mulches lost 195% more mass than the PLA mulch. Cumulative microbial respiration in the PLA-A and PLA-S mulch microcosms was 245% and 239% greater than respiration in PLA mulch microcosms. Cumulative and weekly microbial respiration measurements were similar for PLA and BF treatments. The effects of biostimulants on biodegradation and microbial respiration were inconsistent across mulch treatments. However, Extract PBA increased PLA-A biodegradation by 64% and cumulative microbial respiration by 43% compared to water. These results are consistent with previous research demonstrating correlation between mulch biodegradation and microbial respiration. Overall, results suggest that composite PLA-based biofabrics with embedded plant-based particles degrade more quickly than pure PLA mulches in soil, and that some biostimulant products can further accelerate biodegradation.