Navigating the Socio-Bio-Geo-Chemistry and Engineering of Nitrogen Management in Two Illinois Tile-Drained Watersheds

Abstract

Reducing nitrate loads from corn and soybean, tile-drained, agricultural production systems in the Upper Mississippi River basin is a major challenge that has not been met. We evaluated a range of possible management practices from biophysical and social science perspectives that could reduce nitrate losses from tile-drained fields in the Upper Salt Fork and Embarras River watersheds of east-central Illinois. Long-term water quality monitoring on these watersheds showed that nitrate losses averaged 30.6 and 23.0 kg nitrate N ha -1 yr -1 (Embarras and Upper Salt Fork watersheds, respectively), with maximum nitrate concentrations between 14 and 18 mg N L -1 . With a series of on-farm studies, we conducted tile monitoring to evaluate several possible nitrate reduction conservation practices. Fertilizer timing and cover crops reduced nitrate losses (30% reduction in a year with large nitrate losses), whereas drainage water management on one tile system demonstrated the problems with possible retrofit designs (water flowed laterally from the drainage water management tile to the free drainage system nearby). Tile woodchip bioreactors had good nitrate removal in 2012 (80% nitrate reduction), and wetlands had previously been shown to remove nitrate (45% reductions) in the Embarras watershed. Interviews and surveys indicated strong environmental concern and stewardship ethics among landowners and farmers, but the many financial and operational constraints that they operate under limited their willingness to adopt conservation practices that targeted nitrate reduction. Under the policy and production systems currently in place, large-scale reductions in nitrate losses from watersheds such as these in east-central Illinois will be difficult.

Temperature and Substrate Control Woodchip Bioreactor Performance in Reducing Tile Nitrate Loads in East-Central Illinois

“…fields in the upper Midwest of the United States is a well-established environmental issue (e.g., David et al, 2010). Many in-field and edge-of-field techniques have been proposed and evaluated for reducing these nitrate losses, including fertilizer management, cover crops, perennial crops, water table management, constructed wetlands, buffer strips, two-stage ditches, saturated buffers, and bioreactors (e.g., USEPA, 2008;Schipper et al, 2010b;Skaggs et al, 2012;Jaynes and Isenhart, 2014;David et al, 2015;Groh et al, 2015). The effectiveness of these practices is variable from location to location and temporally due to differing tile flow amounts and nitrate concentrations.…”

“…We installed two bioreactors in the Embarras River watershed in east-central Illinois, the site of extensive previous work on tile drainage and nitrate loss (e.g., David et al, 1997David et al, , 2015Gentry et al, 2014). The watershed has extensive poorly and very poorly drained Mollisols that are typically tile drained and would be an excellent candidate for using wood chip bioreactors to reduce riverine nitrate loads that average 30 kg N ha −1 yr −1 (Gentry et al, 2014).…”

“…Daily precipitation data were obtained from two nearby sites located to the southwest (Tuscola) and the northeast (Philo) of the Bioreactor 1 field and averaged (MRCC, 2015). We installed Bioreactor 1 in March 2012 on a patterndrained 20-ha field with Drummer series soils (fine-silty, mixed, superactive, Mesic Endoaquolls) in a corn and soybean rotation; Year 1 results were reported in David et al (2015). Seed corn fertilized with 168 kg N ha −1 as anhydrous ammonia at planting was grown during 2012, but, due to the severe drought and poor crop yield, the seed corn was not harvested.…”

“…Based on a process-based bioreactor performance model, Bioreactor 1 would have needed to be 9 times as large as the current system to remove 50% of the nitrate load from this 20-ha field. et al, 2010b;Skaggs et al, 2012;Jaynes and Isenhart, 2014;David et al, 2015;Groh et al, 2015). The effectiveness of these practices is variable from location to location and temporally due to differing tile flow amounts and nitrate concentrations.…”

Nutrients in the nexus

“…Analyzing data from the USDA Agricultural Resource Management Survey (ARMS) of corn growers, Weber and McCann (2015) reported that of the 1840 observations, 27 % of the farmers in the study received their application recommendations from a fertilizer retailer, whereas 50 % said they did not receive any recommendations from anyone. In a survey of Illinois farmers, David et al (2015) found that out of pocket expenses were quoted as being the greatest factor that limited farmers' ability and willingness to implement water quality nutrient management, followed closely by lack of government funds for cost sharing and concerns about reduced yields. They indicated that financial incentives and more readily available evidence to demonstrate effective local pollution reduction would have the greatest effect on adoption rates.…”