Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGING AGRICULTURAL WATER QUALITY IN FIELDS AND WATERSHEDS: NEW PRACTICES AND TECHNOLOGIES Title: Reconnecting tile drainage to riparian buffer hydrology for enhanced nitrate removal

Authors
item Jaynes, Dan
item Isenhart, Tom -

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 13, 2014
Publication Date: February 17, 2014
Citation: Jaynes, D.B., Isenhart, T.M. 2014. Reconnecting tile drainage to riparian buffer hydrology for enhanced nitrate removal. Journal of Environmental Quality. 43:631-638.

Interpretive Summary: Streamside buffers are a proven practice for removing the nutrient nitrate from both overland flow and shallow groundwater before it can enter the stream. However, in landscapes with tile drainage most of the subsurface flow leaving farmers’ fields is passed through the buffers in tiles leaving little opportunity for nitrate removal. We investigated the feasibility of re-routing a fraction of field tile drainage as subsurface flow through a riparian buffer for increasing nitrate removal. In the first two years, over 18,000,000 liters (475,000 gal) or 55% of the total flow from the tile outlet was infiltrated as shallow groundwater within the riparian buffer. The infiltrated tile flow contained 228 kg (500 lbs) of nitrate which was completely removed within the buffer and did not enter the stream. Re-directing tile drainage as subsurface flow through a riparian buffer increased the buffer’s nitrate removal benefit and is a promising management practice for farmers interested in improving surface water quality within tile-drained, agricultural landscapes. Wide-scale adoption of the practice will benefit the Nation through reduced nitrate pollution of surface waters.

Technical Abstract: Riparian buffers are a proven practice for removing NO3 from both overland flow and shallow groundwater. However, in landscapes with artificial subsurface (tile) drainage most of the subsurface flow leaving fields is passed through the buffers in drainage pipes leaving little opportunity for NO3 removal. We investigated the feasibility of re-routing a fraction of field tile drainage as subsurface flow through a riparian buffer for increasing NO3 removal. We intercepted an existing field tile outlet draining a 10.1 ha area of a row cropped field in central Iowa, USA, and re-routed a fraction of the discharge as subsurface flow along 335 m of an existing riparian buffer. Tile drainage from the field was infiltrated through a perforated pipe installed 75 cm below the surface by maintaining a constant head in the pipe at a control structure installed in-line with the existing field outlet. During two years, over 18,000 m3 or 55% of the total flow from the tile outlet was redirected as infiltration within the riparian buffer. The redirected water seeped through the 60-m wide buffer, raising the watertable approximately 35 cm. The redirected tile flow contained 228 kg of NO3. Based on the strong decrease in NO3 concentrations within the shallow groundwater across the buffer, we hypothesize that all the NO3 was removed within the buffer either by plant uptake, microbial immobilization, or denitrification and did not enter the stream. Re-directing tile drainage as subsurface flow through a riparian buffer increased its NO3 removal benefit and is a promising management practice to improve surface water quality within tile-drained landscapes.

Last Modified: 9/22/2014
Footer Content Back to Top of Page