Does Quantity and Quality of Tile Drainage Water Impact In-stream Eutrophication Potential? Evidence from a Long-term Biofuel Cropping Systems Experiment

October 25, 2017

Marshall McDaniel, Mriganka De, Michael Thompson, Matt Liebman, Matthew Helmers

Issue: 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 in excess can lead to eutrophication. Tile drainage is used extensively across the U.S. Midwest, and these tile drainage lines can directly transport nutrients to streams. 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 only on the quantity of total dissolved and inorganic forms of N and P. This may not provide the whole story of how tile drainage water can affect stream water quality. Objective: This project will measure chemical composition and eutrophication potential of subsurface drainage (tile-flow) from a variety of management practices. The goal is to look at how management practices affect the quality of tile drainage water resulting from soil N and P cycling and losses, and how that quality directly relates to in-stream water eutrophication. Approach: Tile drainage water samples will be collected and analyzed from an ongoing, long-term experiment in central Iowa called the Comparison of Biofuel Cropping Systems (COBS). The COBS experiment consists of five treatments: continuous corn, corn-soybean, corn with cover crop, fertilized prairie, and unfertilized prairie.

Grant provided by: The Iowa Nutrient Research Center