255-6 Illinois Stream Nitrate Concentrations and Loads: Response to Fall Fertilization.

See more from this Division: S04 Soil Fertility & Plant Nutrition
See more from this Session: Nutrient Losses
Tuesday, October 18, 2011: 2:35 PM
Henry Gonzalez Convention Center, Room 213B
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Mark B. David, Natural Resources and Environmental Sciences, University of Illinois, Urbana, IL and Lowell Gentry, Natural Resources & Environmental Sciences, University of Illinois at Urbana-Champaign, Urbana, IL
Tile drained fields in the upper Midwest are a major source of nitrate to the Gulf of Mexico. Winter/spring nitrate loads in the Mississippi River are a major cause of the Gulf of Mexico hypoxic zone that forms each summer. We utilized long-term stream monitoring data from several east-central Illinois agricultural watersheds to examine the recent response in nitrate concentrations and loads. These watersheds are dominantly corn and soybean, with average nitrate-N loads of 30 kg N/ha/yr. Due to wet conditions in the fall of 2009, little fall N fertilizer was applied in this area (where typically > 50 is fall applied). Fall 2010 had typical fertilization patterns, with extensive application of anhydrous ammonia to many fields. In 2010 we observed the lowest stream water nitrate concentrations (< 10 mg nitrate-N/L in all streams, with many only 4-6 mg N/L) in our period of record (1993 through 2010). In early 2011 nitrate concentrations in all monitored rivers were 7 to 56% greater, with several above 10 mg N/L. Our long-term record and the events of 2009-2011 demonstrates the complex nature of nitrate leaching from tile drained agricultural fields, and how quickly changes can occur in response to a factor such as fall N.
See more from this Division: S04 Soil Fertility & Plant Nutrition
See more from this Session: Nutrient Losses