Exploring saturated drainageways for nitrate reduction in tile-drained agricultural lands

This study evaluates the effectiveness of a saturated grassed waterway as a nitrate (NO₃⁻N) reduction practice in agricultural landscapes. Conducted in a 130-ha field in Black Hawk County, Iowa, the research monitored flow and NO₃⁻N concentration to quantify mass loss within the drainageway. The study site featured a grassed waterway established in the 1970s, which was modified to function as a saturated buffer by diverting tile drainage into a perforated distribution line. From January to May 2024 16% of the total tile flow was diverted into the drainageway, resulting in an average infiltration rate of 0.01 m day-1. NO₃⁻N concentrations in tile drainage water ranged from 5.3 mg L-1 to 27.2 mg L-1, averaging 13.9 mg L-1. The diverted flow resulted in a significant reduction of NO₃⁻N concentrations, with a 97% decrease from the distribution line to the monitoring wells 6.5 meters away. The total mass of NO₃⁻N removed within the drainageway was 166 kg N, representing a 96% reduction in diverted load. These findings support the broader applicability of saturated drainageways as effective NO₃⁻N reduction hotspots, especially in areas with organic-rich soils. The study highlights the potential for utilizing nitrate loss hotspots in various landscape positions to improve water quality. Further research is needed to explore long-term performance and optimal design practices for these systems.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

thesis

Discipline thesis:degree_discipline

Environmental science

Department dc:contributor.department

Department of Natural Resource Ecology and Management

Grantor

Iowa State University

Year dc:date.issued

2024

Author dc:creator

• Merryman, Jennifer Rene

Advisors dc:contributor.advisor

• Isenhart, Thomas M
• Schilling, Keith E
• Moore, Peter L

Language dc:language.iso

en

DOI

https://doi.org/10.31274/td-20250502-319

OAI identifier oai:identifier

oai:dr.lib.iastate.edu:20.500.12876/JvNVPAev