Denitrification in the vadose zone: Modelling with percolating water prognosis and denitrification potential

Lenhart, Simon; Ortmeyer, Felix; Banning, Andre

doi:10.1016/j.jconhyd.2021.103843

Cited by 5 publications

(2 citation statements)

References 26 publications

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“…However, a concomitant increase in riverine N exports from the Willamette River Basin has not been observed (Metson et al, 2020) prompting questions about the fate of surplus N. Soil surplus N can be lost through gaseous releases, such as via the process of denitrification, leached to the groundwater, or accumulated within the soil profile. Denitrification, or the process by which nitrate is sequentially reduced to molecular dinitrogen under mostly anaerobic conditions, largely depends on various factors like soil type, reduction capacity, degree of saturation, and water residence time (Lenhart et al, 2021;Oh et al, 2023), which can impact oxygen concentrations and the presence of electrons donors (i.e., reactive organic carbon or reduced minerals). However, most studies in agricultural settings have shown that denitrification tends to be very limited in the unsaturated vadose zone (Green et al, 2008;Onsoy et al, 2005;Parkin & Meisinger, 1989;Rivett et al, 2007;.…”

Section: Core Ideasmentioning

confidence: 99%

Vadose zone flushing of fertilizer tracked by isotopes of water and nitrate

Weitzman,

Brooks,

Compton

et al. 2024

Vadose Zone Journal

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A substantial fraction of nitrogen (N) fertilizer applied in agricultural systems is not incorporated into crops and moves below the rooting zone as nitrate (NO3−). Understanding mechanisms for soil N retention below the rooting zone and leaching to groundwater is essential for our ability to track the fate of added N. We used dual stable isotopes of nitrate (δ15N–NO3− and δ18O–NO3−) and water (δ18O–H2O and δ2H–H2O) to understand the mechanisms driving nitrate leaching at three depths (0.8, 1.5, and 3.0 m) of an irrigated corn field sampled every 2 weeks from 2016 to 2020 in the southern Willamette Valley, Oregon, USA. Distinct periods of high nitrate concentrations with lower δ15N–NO3− values indicated that a portion of that nitrate was from recent fertilizer applications. We used a mixing model to quantify nitrate fluxes associated with recently added fertilizer N versus older, legacy soil N during these “fertilizer signal periods.” Nitrate leached below 3.0 m in these periods made up a larger proportion of the total N leached at that depth (∼52%) versus the two shallower depths (∼13%–16%), indicating preferential movement of recently applied fertilizer N through the deep soil into groundwater. Further, N associated with recent fertilizer additions leached more easily when compared to remobilized legacy N. A high volume of fall and winter precipitation may push residual fertilizer N to depth, potentially posing a larger threat to groundwater than legacy N. Optimizing fertilizer N additions could minimize fertilizer losses and reduce nitrate leaching to groundwater.

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Section: Core Ideasmentioning

confidence: 99%

Vadose zone flushing of fertilizer tracked by isotopes of water and nitrate

Weitzman,

Brooks,

Compton

et al. 2024

Vadose Zone Journal

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“…Excess N, which is not assimilated by plants, is then transported in large quantities as NO 3 − to groundwater (Sebilo et al 2013 ; Baram et al 2017 ). Lenhart et al ( 2021 ) modeled this transport of NO 3 − through the vadose zone. Due to climate change and a resulting decrease in water resources in many regions, further increases in NO 3 − concentrations are expected in the future (Fleck et al 2017 ; Ortmeyer et al 2021a ).…”

Section: Introductionmentioning

confidence: 99%

Modified microbiology through enhanced denitrification by addition of various organic substances—temperature effect

Ortmeyer

Guerreiro

Begerow

et al. 2023

Environ Sci Pollut Res

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Worldwide, the environmental nitrate (NO3−) problem is increasingly coming into focus. These increases in NO3− concentration result mainly from agricultural inputs and are further exacerbated by decreasing and finite geogenic NO3− degradation capacity in aquifers. Thus, treatment methods are becoming more and more important. In this study, the effects of enhanced denitrification with addition of organic carbon (C) on thereby autochthonous occurring microbiology and compared at room temperature as well as 10 °C were investigated. Incubation of bacteria and fungi was carried out using natural sediments without degradation capacity and groundwater with high NO3− concentrations. Addition of the four applied substrates (acetate, glucose, ascorbic acid, and ethanol) results in major differences in microbial community. Cooling to 10 °C changes the microbiology again. Relative abundances of bacteria are strongly influenced by temperature, which is probably the explanation for different denitrification rates. Fungi are much more sensitive to the milieu change with organic C. Different fungi taxa preferentially occur at one of the two temperature approaches. Major modifications of the microbial community are mainly observed whose denitrification rates strongly depend on the temperature effect. Therefore, we assume a temperature optimum of enhanced denitrification specific to each substrate, which is influenced by the microbiology.

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