Documenting the types and extent of conservation practices in a watershed is necessary to determine their water quality impacts. A conservation practice inventory for the South Fork of the Iowa River, 85% in corn (Zea mays L.) and soybean [Glycine max L. (Merr.)] rotations, showed only 7% of cropland was managed using no-tillage. About 30% of cropland receives manure annually, prior to corn. Su...

Best management practices (BMPs) are widely promoted in agricultural watersheds as a means of improving water quality and ameliorating altered hydrology. We used a paired watershed approach to evaluate whether focused outreach could increase BMP implementation rates and whether BMPs could induce watershed-scale (4000 ha) changes in nutrients, suspended sediment concentrations, or hydrology in a...

Chloride is a relatively unreactive plant nutrient that has long been used as a biogeochemical tracer but also can be a pollutant causing aquatic biology impacts when concentrations are high, typically from rock salt applications used for deicing roads. Chloride inputs to watersheds are most often from atmospheric deposition, road salt, or agricultural fertilizer, although studies on agricultur...

In this study, a set of nitrogen reduction strategies were modeled to evaluate the feasibility of improving water quality to meet total maximum daily loads (TMDLs) in two agricultural watersheds. For this purpose, a spatial-process model was calibrated and used to predict monthly nitrate losses (1994-96) from Sand and Bevens Creek watersheds located in south-central Minnesota. Statistical compa...

Constructed wetlands positioned in the landscape between row crop agriculture and surface waters can be used to intercept tile drainage and serve as agricultural waste water detention basins. A potential exit pathway in constructed wetlands for detained water and possibly NO3 -N is via seepage through and under an earthen berm. The objective of this study was to determine if seepage was an impo...

The quality of water draining fields fertilized with liquid swine (Sus scrofa) manure (LSM) sidedressed into standing corn (Zea mays L.) at rates ranging from 0 to 94 m(3) ha(-1), either topdressed (TD) onto the surface, or injected (INJ) into the soil once annually for each of three consecutive years was evaluated. Liquid swine manure application rate was a critical driver of preferential flow...

Tillage influences N fate and transport by changing soil structure, aeration, macropore continuity, plantresidue placement, and organic-matter mineralization rates. Our objective was to use 15-year N budgets to compare four primary tillage treatments for continuous corn (Zea mays L.) production on tile-drained Aquic Hapludolls (FAO: Haplic Phaeozems) in northeastern Iowa, USA. A carbon-based N ...