Submitted to: Forest Ecology and Management
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/18/2004
Publication Date: 3/6/2005
Citation: Shogren, R.L., Rousseau, R.J. 2005. Field testing of paper/polymerized vegetable oil mulches for enhancing growth of eastern cottonwood trees for pulp. Forest Ecology and Management. Available from: http://authors.elsevier.com/sd/article/S0378112704008229 ScienceDirect. Interpretive Summary: New bio-based products from corn and soybeans are desirable since they provide new markets for surplus, renewable agricultural commodities and reduce use of imported petroleum. Petroleum-based polyethylene film is extensively used in the U.S. to promote growth of vegetables, fruits, trees and shrubs. A bio-based mulch film which stops weed growth and later biodegrades in soil after use would be a desirable alternative to the large amount of non-degradable polyethylene film currently being used. It was found that brown kraft paper coated with a resin made from cured soybean or linseed oils promoted the growth of cottonwood tree cuttings as well as black plastic film for the first year. At the end of the year, disintegration of the coated paper mulch had begun while the plastic mulch was still intact. These results are important to farmers and foresters since it would allow them to avoid the cost of removal of polyethylene from the field after harvest and avoid problems with residual black plastic in harvested wood pulp. The results are also useful to scientists and oilseed processors looking for new uses for vegetable oils.
Technical Abstract: 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 remove non-degradable polyethylene mulches prior to harvest and replanting.