scholarly journals Effects of Subsurface Drainage Systems on Water and Nitrogen Footprints Simulated with RZWQM2

2018 ◽  
Vol 61 (1) ◽  
pp. 245-261 ◽  
Author(s):  
Kristina J. Craft ◽  
Matthew J. Helmers ◽  
Robert W. Malone ◽  
Carl H. Pederson ◽  
Linda R. Schott
Keyword(s):  
Gulf Of Mexico ◽  
Field Data ◽  
Subsurface Drainage ◽  
Drainage Water ◽  
N Loss ◽  
Drainage Systems ◽  
Northern Gulf Of Mexico ◽  
Drainage Water Management ◽  
N Loading

Abstract. Developing drainage water management (DWM) systems in the Midwest to reduce nitrogen (N) transport to the northern Gulf of Mexico hypoxic zone requires understanding of the long-term performance of these systems. Few studies have evaluated long-term impacts of DWM, and the simulation of controlled drainage (CD) with the Root Zone Water Quality Model (RZWQM) is limited, while shallow drainage (SD) has not been examined. We tested RZWQM using nine years (2007-2015) of field data from southeast Iowa for CD, SD, conventional drainage (DD), and undrained (ND) systems and simulated the long-term (1971-2015) impacts. RZWQM accurately simulated N loss in subsurface drainage, and the simulations agreed with field data that CD and SD substantially reduced N loss to drainage. As indicated by the field data, the SD N concentration was predicted to be greater than DD and CD, likely due to reduced time of travel to shallower drains. The long-term simulations show that CD and SD reduced annual N lost via tile drainage by 26% and 40%, respectively. Annual reductions in N lost via tile drainage ranged from 28% in the driest years to 22% in the wettest years for CD and from 56% in the driest years to 35% in the wettest years for SD. Considering spring N loading for the purpose of addressing hypoxia in the Gulf of Mexico, CD was found to be less effective than SD, and in many years CD exported more N in the spring than DD. Spring N loading (April through June) was indicated by the EPA Science Advisory Board to have the greatest impact on hypoxia in the northern Gulf of Mexico. Therefore, improvement of CD systems within the months of April through June to reduce N loss via drainage across the upper Midwest landscape may be required. Limited research in the upper Midwest has addressed spring N loading under controlled drainage systems (CD). This research will help model developers, model users, and agricultural scientists more clearly understand N transport under different systems, including CD, SD, and ND, which will aid in developing the design and management of drainage systems to reduce N transport from tile-drained agriculture to surface waters. Keywords: Agricultural simulation model, Drainage water management, Nonpoint-source pollution, Northern Gulf of Mexico hypoxic zone, Nutrient reduction, Subsurface drainage.

Impact of drainage type on simultaneous nitrogen losses in Atlantic Canada

2019 ◽  
Vol 99 (1) ◽  
pp. 70-79
Author(s):  
Erin L. Smith ◽  
Amanda Vosman ◽  
Lisa Kellman ◽  
Vernon Rodd
Keyword(s):  
Nitrous Oxide ◽  
Crop Yields ◽  
Drainage Water ◽  
Economic Losses ◽  
Controlled Drainage ◽  
N Losses ◽  
Drainage Systems ◽  
N Loading ◽  
Conventional Systems ◽  
Insight Into

Nitrogen (N) losses from agricultural tile drainage systems are environmental and economic losses for producers. This field study quantified N losses from three reps of shallow (SD), deep/conventional (DD), and controlled drainage (CD) on farmland in Nova Scotia. Drainage systems were under corn and alfalfa–oats–clover production. Outflow water and gas samples were obtained and analyzed for nitrate and nitrous oxide. Nitrate-N loads were 5.0, 11.1, and 6.4 kg ha−1 in 2015; 1.8, 6.7, and 2.8 kg ha−1 in 2016; and 0.74, 1.8, and 1.6 kg ha−1 in 2017 for SD, DD, and CD, respectively. Controlled drainage reduced NO3−-N loading by 42.3%–58.2% when compared with the conventional/DD in 2 of 3 yr of study, whereas SD was found to reduce NO3−-N loading by 54.9%–73.1% compared with DD in all years studied. Total NO3−-N losses in this study were measured during the growing season (1 Apr. to 31 Oct.); the magnitude of NO3−-N losses and treatment effects may vary if studied year-round. Nitrous oxide fluxes were variable and low in magnitude throughout the study. Cumulated N2O losses were <1% of the applied N for all drainage types. Controlled drainage increased yields compared with SD and DD. The use of CD in the region could aid in reducing climate stresses, as well as overall NO3−-N loads exiting drainage systems and may enhance crop yields compared with conventional systems. Future studies on dissolved N2O losses from drainage water may provide important insight into whether dissolved N2O losses exceed surface emissions.

scholarly journals Extensive reproductive disruption, ovarian masculinization and aromatase suppression in Atlantic croaker in the northern Gulf of Mexico hypoxic zone

2011 ◽  
Vol 279 (1726) ◽  
pp. 28-38 ◽  
Author(s):  
Peter Thomas ◽  
Md. Saydur Rahman
Keyword(s):  
Gulf Of Mexico ◽  
Mississippi River ◽  
Aromatase Activity ◽  
Northern Gulf Of Mexico ◽  
Hypoxia Exposure ◽  
Hypoxic Zone ◽  
Seasonal Hypoxia ◽  
Reproductive Disruptions ◽  
Reproductive Disruption

The long-term impacts on marine ecosystems of the recent dramatic worldwide increase in the incidence of coastal hypoxia are unknown. Here, we show widespread reproductive disruption in Atlantic croakers collected from hypoxic sites approximately 120 km apart in the extensive northern Gulf of Mexico continental shelf hypoxic zone. Gonadal growth and gamete production were impaired in croakers from hypoxic sites compared with fish from reference normoxic sites east of the Mississippi River Delta. Male germ cells were detected in approximately 19 per cent of croaker ovaries collected in the hypoxic region, but were absent in ovaries from normoxic sites. In addition, the sex ratio was skewed towards males at the hypoxic sites. The masculinization and other reproductive disruptions were associated with declines in neuroendocrine function, as well as ovarian and brain expression of aromatase (the enzyme that converts androgens to oestrogens). A similar incidence of ovarian masculinization and decline in ovarian aromatase expression were observed in croaker after chronic laboratory hypoxia exposure, indicating that ovarian masculinization is a specific hypoxia response and is due to decreased aromatase activity. The results suggest severe reproductive impairment can occur over large coastal regions in marine fish populations exposed to seasonal hypoxia, with potential long-term impacts on population abundance.

scholarly journals Long-Term Observations of Epibenthic Fish Zonation in the Deep Northern Gulf of Mexico

PLoS ONE ◽  
2012 ◽  
Vol 7 (10) ◽  
pp. e46707 ◽  
Author(s):  
Chih-Lin Wei ◽  
Gilbert T. Rowe ◽  
Richard L. Haedrich ◽  
Gregory S. Boland
Keyword(s):  
Gulf Of Mexico ◽  
Northern Gulf Of Mexico
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