Urea Fluctuations in Stream Baseflow across Land Cover Gradients and Seasons in a Coastal Plain River System

Tzilkowski, Sarah Suzanne; Buda, Anthony R.; Boyer, E. W.; Bryant, Ray B.; Kleinman, Peter J. A.; Kennedy, Casey D.; Allen, Arthur L.; Folmar, Gordon J.; May, Eric

doi:10.1111/1752-1688.12716

Cited by 6 publications

(17 citation statements)

References 63 publications

(141 reference statements)

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“…Additionally, the annual median urea-N concentration was highest during 2016 (0.06 mg N L −1 ) but ranged from 0.04 to 0.06 mg N L −1 from 2015 to 2018 (data not shown). These annual median urea-N concentrations concur with the median concentration of 0.05 mg N L −1 reported from a single field ditch site in the Tzilkowski et al (2019) synoptic watershed study. Ammonium-N concentrations followed a pattern similar to urea; higher concentrations in summer and lower concentrations in spring and fall.…”

Section: Urea-n Concentrations By Month Season and Yearsupporting

confidence: 84%

“…The positive relationship between urea‐N concentrations and temperature has been found in bottom waters of lakes (Bogard, Donald, Finlay, & Leavitt, 2012); tidal and nontidal streams (Tzilkowski et al., 2019); and drainage ditch, forest, and wetland sediments during a mesocosm experiment (King et al., 2017). Urea‐N accumulation in low oxygen and redox environments has also been reported in the bottom waters of lakes and within waterlogged sediments (Bogard et al., 2012; Pulford & Tabatabai, 1988).…”

Section: Resultsmentioning

confidence: 93%

“…Although dilution may occur, the resulting urea‐N concentrations may still be environmentally relevant. Thus, drainage ditches should be considered a potential source of urea‐N accumulation in coastal waters, concurrent with in situ urea formation in forested and open wetlands (Tzilkowski et al., 2019). Climate change scenarios have predicted more frequent and intense storm events, emphasizing the need for better management of urea‐N accumulation in agricultural drainage ditches.…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies found urea‐N concentrations in the Chesapeake Bay and its tributaries to vary based on season, depth, and proximity to agricultural land on the Eastern Shore of Maryland (Glibert, Trice, Michael, & Lane, 2005; Lomas, Trice, Glibert, Bronk, & McCarthy, 2002). Urea‐N concentrations within the Manokin River Watershed were recently associated with higher proportions of wetlands under baseflow conditions (Tzilkowski et al., 2019). Although fertilizer inputs play a major role in urea‐N loading (Glibert et al., 2006), more recent findings suggest that biologically driven processes associated with wetlands are also a very influential component (Tzilkowski et al., 2019).…”

Section: Introductionmentioning

confidence: 99%

“…Urea‐N concentrations within the Manokin River Watershed were recently associated with higher proportions of wetlands under baseflow conditions (Tzilkowski et al., 2019). Although fertilizer inputs play a major role in urea‐N loading (Glibert et al., 2006), more recent findings suggest that biologically driven processes associated with wetlands are also a very influential component (Tzilkowski et al., 2019). However, uncertainties remain regarding the fate, transport, and balance between external inputs and regeneration of urea‐N from agricultural environments.…”

Section: Introductionmentioning

confidence: 99%

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Seasonal and temporal factors leading to urea‐nitrogen accumulation in surface waters of agricultural drainage ditches

et al. 2020

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Urea‐nitrogen (N) is commonly applied to crop fields, yet it is not routinely monitored despite its association with reduced water quality and its ability to increase toxicity of certain phytoplankton species. The purpose of this work was to characterize temporal fluctuations in urea‐N concentrations and associated environmental conditions to infer sources of urea‐N in agricultural drainage ditches. Physicochemical properties and N forms in ditch waters were measured weekly during the growing seasons of 2015–2018. Fertilizer application was only associated with spring peaks of urea‐N concentrations in ditches next to cornfields, whereas summer peaks in ditches adjacent to corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] fields were not associated with fertilizer applications. Environmental conditions of warmer temperatures, lower dissolved oxygen concentrations, and lower redox potentials were correlated with higher urea‐N concentrations. In 2018, peaks of urea‐N and ammonium‐N during the summer co‐occurred with peaks of dissolved organic N and total dissolved N, suggesting they might be associated with the breakdown of organic matter and with the turnover of the organic N pool. Although the highest urea‐N concentrations occurred when ditch surface waters were hydrologically disconnected from nearby streams, heavy rainfalls can potentially flush accumulated urea‐N into coastal waters, where it may affect algal bloom toxicity. Therefore, implementation of available drainage ditch management practices is recommended, but these strategies need to be optimized for targeting periods with high rainfall that coincide with fertilizer additions as well as for periods with low rainfall that promote stagnant water conditions.

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Section: Urea-n Concentrations By Month Season and Yearsupporting

confidence: 84%

Section: Resultsmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Seasonal and temporal factors leading to urea‐nitrogen accumulation in surface waters of agricultural drainage ditches

et al. 2020

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Natural sources and controlling factors of urea–nitrogen concentrations in agricultural drainage ditches

et al. 2023

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Agricultural drainage ditches accumulate high urea–nitrogen (N) concentrations even in the absence of urea fertilizer applications to adjacent crop fields. The accumulated urea, and other bioavailable forms of dissolved organic nitrogen (DON), can be flushed downstream during substantial rainfall events altering downstream water quality and phytoplankton communities. Sources of urea–N supporting its accumulation in agricultural drainage ditches are poorly understood. A ditch flooding event was simulated using mesocosms with N treatment solutions and monitored for changes in N concentrations, physicochemical properties, dissolved organic matter (DOM) composition, and N cycling enzymes. N concentrations were also monitored in field ditches after two rainfall events. Urea–N concentrations were higher with DON enrichment, but the treatment effects were temporary. The DOM released from the mesocosm sediments was dominated by terrestrial‐derived, high molecular weight material. The lack of microbial‐derived DOM and evidence from the bacterial gene abundances in the mesocosms suggests that urea–N accumulation after rainfall may not be associated with fresh biological inputs. The urea–N concentrations after spring rainfall and flooding with DON substrates indicated the urea from fertilizers may only temporarily affect urea–N concentrations in drainage ditches. Because urea–N concentrations increased with a high degree of DOM humification, sources of urea may derive from the slow decomposition of complex DOM structures. This study provides further insights of sources contributing to high urea–N concentrations and the types of DOM released from drainage ditches to nearby surface waters after hydrological events.

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Spatial and temporal patterns of urea content in a eutrophic stream continuum on the Northern Great Plains

2021

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Urea can degrade water quality and stimulate toxic phytoplankton in P-rich lakes, yet little is known of its sources, abundance, or transportation in lotic systems, particularly within the Northern Great Plains. We measured physico-chemical parameters biweekly during May–September 2010–2012 at 16 stations along a 250 km lotic continuum to quantify spatial and temporal variation in urea concentrations and discharge, and to identify potential regulatory processes. Urea concentrations were similar to those in regional prairie lakes (range 5.2–792.1, median 78.6 μg N L−1) with variable seasonal mean (± SD) concentrations (96.6 ± 96.1 μg N L−1) and fluxes (4.22 × 105 ± 257.6 μg N s−1). Landscape analysis with generalized additive models explained 68.3% of deviance in urea concentrations, with high temporal variability predicted mainly by positive relationships with nutrient content and chlorophyte abundance, but not temperature, dissolved organic matter, bacterial abundance, or urban effluent. Seasonal analysis revealed that during spring, urea content was correlated negatively with leguminous forage cover (% area) and positively with stream discharge, oilseed and cereal crops, and shrubs or deciduous plants, while during summer, urea concentrations were correlated negatively with discharge and leguminous crop cover, as well as nutrient levels. Mean porewater urea concentrations (528.5 ± 229.8 μg N L−1) were over five-fold greater than stream concentrations, suggesting that hyporheic production may offset declining influx from terrestrial sources during summer. We conclude that urea may be ubiquitous in eutrophic prairie streams and that management of its export from land may reduce detrimental effects on downstream lakes.

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Urea Fluctuations in Stream Baseflow across Land Cover Gradients and Seasons in a Coastal Plain River System

Cited by 6 publications

References 63 publications

Seasonal and temporal factors leading to urea‐nitrogen accumulation in surface waters of agricultural drainage ditches

Seasonal and temporal factors leading to urea‐nitrogen accumulation in surface waters of agricultural drainage ditches

Natural sources and controlling factors of urea–nitrogen concentrations in agricultural drainage ditches

Spatial and temporal patterns of urea content in a eutrophic stream continuum on the Northern Great Plains

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