Browsing by Subject "Soil conservation"
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Item Development of agroforestry systems for bioenergy crop production and soil conservation.(2012-10) Gamble, Joshua D.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.Item Quantifying the Impacts of Climate Change on Soil Erosion and Runoff in Minnesota Agricultural Watersheds using the WEPP Model(2022-08) Kohrell, GarnerIn the past several decades, soil water erosion and runoff in agricultural regions across the Midwestern United States have contributed to significant A-horizon soil losses, declining soil productivity, and the widespread impairment of water resources. Rising temperatures and changes in precipitation trends have the potential to significantly impact future soil water erosion and runoff in the Midwest, yet relatively few studies have attempted to quantify these impacts. To help expand this area of research, the Water Erosion Prediction Project (WEPP) Model was used to quantify growing season soil water erosion and runoff for a baseline period (1965-2019) and two future periods (2020-2059 & 2060-2099) in agricultural hillslopes across three Minnesota HUC12 watersheds. Future daily weather inputs were generated for WEPP using downscaled daily climate projections from two CMIP5 climate models (HadGEM2-CC and GFDL-ESM2G) and three emissions scenarios (RCP 4.5, RCP 6.0, and RCP 8.5). The climate scenarios were combined with varying adoption rates of perennial crops, conservation tillage systems, and cover crops in order to determine the effectiveness of these mitigation strategies in reducing future soil loss and runoff. When the baseline management scenario was used, most future climate scenarios showed decreases in runoff (34-58%), soil loss (3.3-40%), and the number of hillslopes with unsustainable soil loss (1-8%). However, there were also moderate to significant increases in runoff (17-38%), soil loss (4.2-40%), and the number of hillslopes with unsustainable soil loss (+3%) in several of the moderate emissions scenarios (RCP 4.5 and RCP 6.0). Watersheds with steep slopes and widespread conventional row crop systems had a significantly greater number of hillslopes with unsustainable soil losses, even if runoff and soil loss were projected to decrease in the future. Additionally, growing season runoff and edge-of-field sediment delivery values required to meet TSS total maximum daily loads (TMDLs) were only met in the highest emissions scenarios (RCP 8.5) where future soil loss and runoff significantly decreased. In order to mitigate agricultural runoff and unsustainable soil losses in Minnesota under current and future climates, we recommend implementing a combination of perennial alfalfa cropping systems and reduced tillage systems across hillslopes in watersheds with widespread steep slopes and conventional row cropping systems. However, requirements for TSS TMDLs were still only met in the highest emissions scenarios when these systems were implemented into the majority of hillslopes. As a result, additional off-site mitigation measures will likely be required in at-risk watersheds to meet TSS TMDLs and soil conservation goals under most future climates.