Effects of biodegradable mulch on soil quality

Biodegradable plastic films are desirable alternatives to traditional black polyethylene plastic for use asmulches in agroecosystems. Efforts are ongoing to engineer biodegradable plastic mulches that could beincorporated into the soil at the end of the crop season, and decomposed by microorganisms, ultimatelyto CO2, H2O, and biomass. Whether changes in soil quality occur during or following biodegradation isunknown. An 18-month study evaluated the effects on soil quality following burial of four potentiallybiodegradable mulches and a no mulch control in high tunnel and open field tomato production systemsacross three geographically distinct locations (Knoxville, TN; Lubbock, TX; Mount Vernon, WA). The mulchtreatments included: two starch-based mulches (BioAgri (R) Ag-Film and BioTelo Agri); one experimental100% polylactic acid mulch (Spunbond-PLA-10); one cellulose-based mulch (WeedGuardPlus; positivecontrol); and a negative control (no mulch). The soil management assessment framework (SMAF) wasused to calculate a soil quality index (SQI) according to five dynamic soil properties: microbial biomasscarbon, beta-glucosidase, electrical conductivity, total organic carbon (TOC), and pH. Within the 18-monthevaluation period, the effects of the biodegradable mulches on the SQI were minor, and dependent uponproduction system and time of incubation at all locations. In general, the SQI was higher in the hightunnel systems for some of the mulch treatments at Knoxville and Lubbock but the opposite was true atMount Vernon. By the final sampling at 18 months, the SQI was lowest for WeedGuardPlus at Lubbockand Mount Vernon but at Knoxville, the WeedGuardPlus SQI was not significantly different from the nomulch control. Of the five SMAF indicators evaluated, soil microbial biomass and beta-glucosidase activitywere the most responsive to mulch and production systems, supporting the use of these variables as soilquality indicators for short-term changes due to this agricultural management practice. (C) 2014 Elsevier B.V. All rights reserved.