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Seasonal hypoxia in the northern Gulf of Mexico has been linked to increased nitrogen fluxes from the Mississippi and Atchafalaya River Basins, though recent evidence shows that phosphorus also influences productivity in the Gulf. We developed a spatially explicit and structurally detailed SPARROW water-quality model that reveals important differences in the sources and transport processes that control nitrogen (N) and phosphorus (P) delivery to the Gulf. Our model simulations indicate that agricultural sources in the watersheds contribute more than 70% of the delivered N and P. However, corn and soybean cultivation is the largest contributor of N (52%), followed by atmospheric deposition sources (16%); whereas...
This paper presents results of a study to assess the impacts of climate change on Midwestern streams and the ability of alternative regulations to maintain critical stream conditions. The study focuses on two generic types of regulations, those that restrict withdrawals to a constant flowrate at all times and those that allow withdrawals to increase and decrease with streamflow. Trading of water withdrawal permits is also considered as an adjunt to both policies. The study uses a modeling technique based on the SWAT model, applied to data for a Midwestern river basin. Streamflow was assumed stressed by agricultural irrigation, which is most intense during times when natural streamflows are at their lowest even without...
Much time and money has been spent over the last 40 years in the U.S. by farmers, soil scientists, hydrologists, geomorphologists, engineers, and ecologists attempting to document how agricultural best management practices, natural vegetation in riparian corridors, and stream rehabilitation or bank stabilization reduces sediment yields and improves ecological conditions at watershed outlets. These issues are especially pertinent in the steep erodible landscape of the Driftless Area in southwest Wisconsin, where many miles of world-class spring-fed trout streams remain on state impaired waters lists from excessive sedimentation and degraded habitat even though this area was the birthplace of the conservation movement...
This project is part of the USDA's Mississippi River Basin Initiative. We are providing the water quality monitoring to assess the impact of various best management practices aimed at reducing nutrient runoff from agricultural lands.
Nitrate N from artificially drained soils of the upper Midwest USA is finding its way to the Mississippi River and then to the Gulf of Mexico. There is some concern that this nitrate N is causing hypoxia in the Gulf of Mexico. The DRAINMOD-N model was used to evaluate the long-term effect of N application rate and drain spacing on corn (Zea mays L.) yield and nitrate N losses. Prior to evaluation, the model was calibrated and then validated against long-term field data from southwestern Minnesota. A 24-yr simulation showed that climate plays a major role in determining drainage, yield, and nitrate N losses from a moderately well-drained Normania clay loam (fine-loamy, mixed, mesic Aquic Hapludoll) soil under continuous...
Alternative cropping systems can improve resource use efficiency, increase corn grain yield, and help in reducing negative impacts on the environment. A 6-yr (1993 to 1998) field study was conducted at the Iowa State University's Northeastern Research Center near Nashua, Iowa, to evaluate the effects of non-traditional cropping systems [strip inter cropping (STR)-corn (Zea mays L.)/soybean (Glycine max L.)/oats (Avena sativa L.)]; alfalfa rotation (ROT)-3-yr (1993 to 1995) alfalfa (Medicago sativa L.) followed by corn in 1996, soybean in 1997, and oats in 1998), and traditional cropping system (corn after soybean (CS) and soybean after corn (SC) on the flow weighted average nitrate-nitrogen (NO3-N) concentrations...
...in adopting various best management practices, but the tool...Environmental Policy Integrated Climate (EPIC) model (Williams...Report 97-SR 85.Ames, Iowa: Center for Agricultural and Rural Development, Iowa State University. http...Demonstration of Phosphorus Best Management Practices in the North...