Decreasing nitrate-N loads to coastal ecosystems with innovative drainage management strategies in agricultural landscapes: An experimental approach

Investigating the role of organic carbon amendments and microbial denitrification gene abundance in nitrogen removal from experimental agricultural drainage ditches with low‐grade weirs

“…At the high‐flow rate, the DOC treatment still had the greatest reduction (27.1%) followed by control (17.2%) and POC (11.6%); this trend was perhaps due to minimal release of organic carbon from Bermudagrass hay under the high‐flow rate. Maximum reduction in the current study was 31% in the ditch with weirs and 23% in the ditch without weirs, which is similar to previous studies using experimental drainage ditches to compare ditches with and without weirs (Kröger, Pierce, Littlejohn, Moore, & Farris, ). Effects of flow rate on ‐N removal in drainage ditches have varied considerably in previous studies, ranging from a 45% increase to a 100% decrease in ‐N concentration (Faust et al, ; Kröger et al, ; Littlejohn et al, ; Robertson & Merkley, ).…”

“…Furthermore, using experimental drainage ditches with the same size dimensions, slope, and plant communities in the study design helped control for similar discharges, which makes comparing nutrient concentrations between ditches useful. Regardless of organic carbon treatment, flow, or presence/absence of weirs, observed reductions in ‐N concentrations from inflow to outflow were much lower than expected based on previous studies of streams and drainage ditches in agricultural landscapes (Kröger et al, , ; Littlejohn et al, ; Robertson & Merkley, ). It is possible that ‐N and organic carbon‐containing overlying water did not have adequate time for exchange into sediments, where denitrification primarily occurs, due to low HRT.…”

Two centuries of nitrogen dynamics: Legacy sources and sinks in the Mississippi and Susquehanna River Basins

“…For the MRB, which is the more legacy-driven system and thus more bound by inertia, short-term gains will be more difficult to achieve. In this case, a targeted short-term approach like the increased use of constructed wetlands to intercept runoff from tile drains and flooding streams [Mitsch et al, 2001] would need to be integrated with longer-term approaches of reductions in N application rates and modification of tile drainage networks to slow the transport of N to nearby waterbodies [Kröger et al, 2012;Drury et al, 2014]. In the SRB, where both animal manure and urban wastewater represent significant current year sources, upgrades to wastewater treatment plants (WWTPs) [Carey and Migliaccio, 2009;Zimmerman and Dooley, 2014] and more innovative forms of manure management, including the development of biogas reactors for both waste treatment and energy production [Weiland, 2006], may have a larger short-term impact.…”

Tiered on-the-ground implementation projects for Gulf of Mexico water quality improvements

“…Since drainage ditches are typically ephemeral in the Lower Mississippi Alluvial Valley, the increased water volume and duration can enhance biological and geochemical conditions for N and P retention and removal. Low-grade weirs enhance hydraulic residence of the drainage ditch, decrease flow velocities, and increase sediment settling and overall nutrient removal (Kröger et al 2011(Kröger et al , 2012. Low-grade weirs can be stair-stepped through the landscape and can provide multiple opportunities within Figure 1 (a) Small edge-of-field structures, such as slotted pipes, can decrease the transport of sediment from fields into primary water bodies by limiting bed-flow sediment.…”