Watershed-scale effects of a novel agricultural conservation practice on atrazine in channelized agricultural headwater streams

Authors: Gonzalez, Javier; Smiley, Peter; Smith, Douglas; Livingston, Stanley

Submitted to: Popular Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2026
Publication Date: 9/30/2026
Citation: Gonzalez, J.M., Smiley, P.C., Smith, D.R., Livingston, S.J. 2026. Watershed-scale effects of a novel agricultural conservation practice on atrazine in channelized agricultural headwater streams. Popular Publication. https://doi.org/10.1002/jeq2.70273.
DOI: https://doi.org/10.1002/jeq2.70273

Interpretive Summary: Atrazine is a common herbicide used in corn production, but it can wash into nearby streams during spring rains and affect water quality. This study looked at whether replacing traditional field drainage structures called tile risers with blind inlets could reduce the amount of atrazine entering streams. Blind inlet is conservation practices that reduces sediment losses and improves water quality by filtering runoff through layers of soil and gravel before water reaches subsurface drainage pipes. Researchers compared the concentrations and amounts of instream atrazine in two agricultural watersheds in northeastern Indiana over eight years. After the tile risers were replaced with blind inlets in one watershed, atrazine levels and related drinking water and aquatic life indexes in the stream during spring storm events were reduced by > 95% compared to the untreated watershed. No differences in atrazine occurred in the summer or fall. These results indicate that replacing tile risers with blind inlets will help reduce springtime herbicide runoff, which makes them a promising conservation practice for improving water quality within agricultural watersheds in the Midwestern United States. These findings will benefit American farmers, producers, and communities as they identify a conservation practice that will protect agricultural drinking water sources and enhance their recreational and subsistence fishing opportunities within agricultural streams. Additionally, the findings will also support conservation efforts led by the Natural Resources Conservation Service (NRCS), including programs such as the Regenerative Pilot Program and the Conservation Effects Assessment Project (CEAP) by providing the NRCS with much needed information on the conservation outcomes associated with a water management practice.

Technical Abstract: There is a need for conservation practices capable of reducing elevated atrazine concentrations that commonly occurs in the spring within agricultural streams of the Midwestern United States. Blind inlets are a novel water control structure that is an alternative to conventional tile risers. Information is lacking on the effect of replacing tile risers with blind inlets on atrazine in channelized agricultural headwater streams at the watershed scale. Our research questions were: 1) does replacing tile risers with blind inlets reduce atrazine concentrations and loads during spates within channelized agricultural headwater streams? and 2) do these effects differ seasonally? We conducted an eight-year before-after-control-impact experiment in two channelized agricultural headwater streams in northeastern Indiana. During the before period (2004–2009) when both watersheds had tile risers, eight atrazine responses variables during spring spates did not differ P > 0.400) between streams. After replacing tile risers with blind inlets in the impact stream (2010–2011), mean and maximum atrazine concentrations, total atrazine loads, mean drinking water toxicity index scores, and mean fish chronic toxicity index scores during spring spates were lower (P < 0.001) in the impact stream compared to the control stream. Additionally, replacing tile risers with blind inlets did not affect any of the atrazine response variables during summer and fall spates. These results indicate that replacing conventional tile risers with blind inlets is an effective conservation practice for reducing elevated springtime atrazine concentrations and loads in channelized agricultural headwater streams in the Midwestern United States.