Tile Drainage and In-stream Eutrophication
Title: Does quantity and quality of tile drainage water impact in-stream eutrophication potential? Evidence from a long-term biofuel cropping systems experiment.
Time Period: 2019-2021
Research Team: Marshall D. McDaniel, Mriganka De, Michael L. Thompson, Matt Liebman, and Matthew J. Helmers
Project Description: The challenge with farming is balancing crop nutrient needs while minimizing losses. Fertilizer nitrogen (N) and phosphorus (P) are added to agricultural fields to increase yields, but these nutrients also limit algal growth in the aquatic ecosystems and in excess can lead to eutrophication. Tile drainage is used extensively across the U.S. Midwest to also improve yields, but these tile drainage lines can directly transport nutrients to streams - effectively bypassing natural stream buffers. The quantity (i.e. load) and quality (i.e. chemical composition of nutrients and carbon) of the tile drainage water likely plays a crucial role in stream water quality, but most tile drainage studies focus on only the quantity of total dissolved and inorganic forms of N and P. This, however, may not be giving us the whole story of how tile drainage water can affect stream water quality. Instead, we propose to delve further into the chemical forms of N and P (and dissolved organic carbon) in tile drainage water, and look at how management practices affect these. Furthermore, we will evaluate the eutrophication potential of the same tile water in order to gain a more comprehensive understanding of the effects of tile drainage water on stream water eutrophication. We will analyze tile drainage water samples from an ongoing, long-term experiment near Boone, IA called the Comparison of Biofuel cropping Systems (or COBS). The COBS experiment consists of five treatments: continuous corn, corn-soybean, corn with cover crop, fertilized prairie, and unfertilized prairie. Our specific research objectives are to:
1. Assess the impact of the five different management practices on chemical composition and bioavailability of dissolved organic matter in tile drainage water.
2. Determine the eutrophication potential of tile drain water from these different management practices.
Funders: Iowa Nutrient Research Center
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