Field testing of paper/polymerized vegetable oil mulches for enhancing growth of eastern cottonwood trees for pulp

Field studies of biodegradable polymerized vegetable oil-coated paper mulches were conducted to determine if these could replace non-degradable polyethylene mulches for stopping weeds and promoting growth of cottonwood trees. Tests were conducted over two growing seasons in two adjacent field sites in southeastern Missouri. At the end of the 2001 season, eastern cottonwood trees grown on the coated paper mulches had average heights (4.57-4.66 m, 15.0-15.3 ft), which were not significantly different from the control black polyethylene mulch (4.75 m, 15.6 ft). Tree heights were significantly less for uncoated paper mulch (4.45 m, 14.6 ft) or no mulch (3.90 m, 12.8 ft), presumably due to heavy weed growth around the trees. Uncoated paper mulch was extensively degraded after only about 4 weeks, while the coated paper persisted until the fall. Addition of ZnO to the oil coating delayed the onset of visible degradation, such as the formation of holes and tears, especially near the buried edge and above the drip tube. Similar results were seen for the 2002 study except that weed growth was not extensive so that tree heights for the mulched and bare plots were not significantly different. These results suggest that polymerized vegetable oil-coated paper mulches can function as effective mulches during the first year of tree growth, and thus, eliminate the need to use non-degradable polyethylene mulches.