Agroforestry systems have been proposed as a means of dedicated bioenergy crop production that can potentially satisfy a broad suite of social, economic, and environmental objectives. Strategic placement of such systems may help to maximize economic returns from marginal crop land and reduce agricultural non-point source pollution. However, little is known about the performance of perennial bioenergy crops in agroforestry systems in the North Central Region. Moreover, the effectiveness of these crops in reducing certain types of agricultural non-point source pollution relative to conventional annual cropping systems is unknown. Therefore, experiments were conducted to 1) evaluate the establishment and productivity of dedicated woody and herbaceous perennial bioenergy crops in riparian alley cropping agroforestry systems, and 2) to evaluate the effects of dedicated perennial bioenergy crops on surface runoff and sediment loss relative to conventional and alternative annual cropping practices.
In the first experiment, basal area of poplar clone ‘NM6’ averaged 1,045 and 1,744 mm2 tree-1 at two sites after two seasons, while that of willow clone ‘Fish Creek’ averaged 770 and 1,609 mm2 tree-1. Prairie cordgrass and a native polyculture were among the most productive herbaceous crops at both sites, averaging between 7.1 and 11.9 Mt ha-1 by the second growing season. During the first two years following establishment, competition for resources did not reduce establishment success or productivity of woody and herbaceous crops along the tree-crop interface. These results suggest that hybrid poplar and willow along with certain herbaceous bioenergy crops may be well suited to alley cropping on riparian sites, though more research is needed to evaluate crop persistence and productivity within the alley cropping environment. In the second experiment, a native grass mixture reduced the average sediment concentration in surface runoff by 87% and 90% relative to a corn-soybean rotation and no-till corn, respectively. Sediment concentrations in surface runoff from short-rotation willow did not differ from the corn-soybean rotation, but were reduced in fall surface runoff by 51% relative to no-till corn. These results suggest that soil conservation can be improved in short-rotation willow systems, but confirm previous findings that native grasses can provide excellent sediment retention relative to annual systems.
University of Minnesota M.S. thesis. October 2012. Major: Natural Resources Science and Management. Advisors:Craig C. Sheaffer, Dean A. Current. 1 computer file (PDF); viii, 85 pages, appendices A-B.
Gamble, Joshua D..
Development of agroforestry systems for bioenergy crop production and soil conservation..
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