Impact of controlled drainage on subsurface drain flow and nitrate load: A synthesis of studies across the U.S. Midwest and Southeast

Authors: HELMERS, MATTHEW - Iowa State University; Abendroth, Lori; REINHART, BENJAMIN - Purdue University; CHIGHLADZE, GIORGI - Iowa State University; PEASE, LINDSAY - University Of Minnesota; BOWLING, LAURA - Purdue University; YOUSSEF, MOHAMED - North Carolina State University; GHANE, EHSAN - Michigan State University; AHIABLAME, LAURENT - University Of California; BROWN, LARRY - The Ohio State University; FAUSEY, NORMAN - Retired ARS Employee; FRANKENBERGER, JANE - Purdue University; JAYNES, DAN - Retired ARS Employee; King, Kevin; KLADIVKO, EILEEN - Purdue University; NELSON, KELLY - University Of Missouri; STROCK, JEFFREY - University Of Minnesota

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2021
Publication Date: 10/20/2021
Publication URL: https://handle.nal.usda.gov/10113/7546149
Citation: Helmers, M.J., Abendroth, L.J., Reinhart, B.D., Chighladze, G., Pease, L., Bowling, L., Youssef, M., Ghane, E., Ahiablame, L., Brown, L., Fausey, N., Frankenberger, J., Jaynes, D., King, K.W., Kladivko, E., Nelson, K., Strock, J. 2021. Impact of controlled drainage on subsurface drain flow and nitrate load: A synthesis of studies across the U.S. Midwest and Southeast. Agricultural Water Management. 259. Article 107265. https://doi.org/10.1016/j.agwat.2021.107265.
DOI: https://doi.org/10.1016/j.agwat.2021.107265

Interpretive Summary: Millions of row crop acres in the U.S. Midwest benefit from subsurface artificial tile drainage installed to reduce waterlogged conditions. However, the presence of this drainage system can have negative environmental impacts such as increased nutrient pollution in nearby streams. Controlled drainage is a practice that limits the amount of water exiting these artificially drained fields by “holding back" the water through the installation of control structures. This research examined the potential reduction in nutrient loss, specifically nitrate-nitrogen, when less water is released during key periods of the year. The use of the control structures did reduce the yearly amount of water (from 28 to 52%) and nitrogen (32 to 37%) leaving the field compared to uncontrolled systems. The amount and timing of the reduction varied within the year based on seasons. More water and corresponding nitrogen were released from the tile drain systems during winter months in eastern Midwest states while the release was greater during the spring months in western and northern states. This difference in timing of water and nutrients leaving row crop fields is due primarily to freeze-thaw timing and rainfall. In areas with greatest spring tile flow, controlled drainage has less usefulness as a water quality strategy due to the need to balance water quality goals with field operations. More water must be released in the spring to allow fields to dry out in time for planting. Therefore, in the western and northern parts of the Midwest, additional conservation practices will be needed to meet springtime water quality goals. This research benefits farmers, scientists, and municipalities by providing an understanding of the timing when highest amounts of water and nitrogen are released and the reduction possible when control structures are installed.

Technical Abstract: Controlled drainage (CD), sometimes called drainage water management, is a practice whereby the drainage system outflow is managed during specific periods to retain more water in the field. Although CD has been shown to reduce downstream nitrate load, seasonal patterns have been less consistent which can potentially impact the effectiveness of conservation practices. The main objective of this study was to assess the regional and seasonal impact of conventional free drainage (FD) and CD on drainage flow and nitrate load. Using experimental data from ongoing and historical CD experiments across the Corn Belt and in North Carolina, we evaluated subsurface drain flow, nitrate load, and performance of CD systems. Across the data set and regions, there was little difference in annual flow from FD conditions. Seasonally, more northern and western sites experienced a greater percentage of the annual flow occurring in the spring. There was no nitrate concentration reduction with CD. Flow and nitrate load reductions with CD did not vary by plant hardiness zone across the region, but the season with the greatest reduction did shift from winter to spring moving north and west in the study area. Drainage flow reductions with CD (in mm) did not vary based on precipitation category and consequently, the percent reduction in nitrate load was lower with higher precipitation. Overall, this analysis found CD to be an effective practice for reducing drain flow and nitrate loading directly delivered by the drains to downstream water bodies across the region.