Cover crops and precipitation influence soluble reactive phosphorus losses via tile drain discharge in an agricultural watershed

Trentman, Matt T.; Tank, Jennifer L.; Royer, Todd V.; Speir, Shannon L.; Mahl, Ursula H.; Sethna, Lienne R.

doi:10.1002/hyp.13870

Cited by 11 publications

(8 citation statements)

References 64 publications

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“…(2015) also observed higher P sorption and lower bioavailable P in one site with higher concentrations of iron oxides than in a nearby site that had lower iron oxides. Furthermore, a companion study found that cover crops were also more effective in reducing P loss from soils to tile drains in SDW than in KDW and attributed these results to the underlying geochemical properties and legacy fertilizer application described above (Trentman et al., 2020).…”

Section: Discussionmentioning

confidence: 98%

“…Differences in geochemical properties between the watersheds could also play a role in the extent to which cover crops affect soil P. Clay soils in KDW are likely more conducive to inorganic P retention because both extractable iron and aluminum are more abundant relative to P (Trentman et al., 2020). This higher abundance of iron and aluminum relative to P allows for more P sorption capacity (Andersson et al., 2015) and reduced potential for cover crop uptake in KDW vs. SDW.…”

Section: Discussionmentioning

confidence: 99%

“…Immobilization of NO 3 – –N reduces NO 3 – –N loss through tile drains to downstream water bodies (Hanrahan et al., 2018; Kladivko et al., 2014). There is less certainty about how cover crops influence P loss to waterways, with some studies reporting reductions (Eichler‐Löbermann et al., 2008; Kovar et al., 2011; Trentman et al., 2020) and others reporting increases (Bergström et al., 2015; Ulén, 1997) or no effect (Liu et al., 2012). In addition, cover crops can increase P stratification in agricultural soil by concentrating bioavailable P in shallow soil layers (Sharpley, 2003), which in turn can increase export of P to surface waters (Baker et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

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Effect of winter cover crops on soil nutrients in two row‐cropped watersheds in Indiana

et al. 2021

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The midwestern United States is a highly productive agricultural region, and extended crop-free periods in winter/spring can result in nitrogen (N) and phosphorus (P) losses to waterways that degrade downstream water quality. Planting winter cover crops can improve soil health while reducing nutrient leaching from farm fields during the fallow period. In this study, we used linear mixed effects models and multivariate statistics to determine the effect of cover crops on soil nutrients by comparing fields with cover crops (n = 9) versus those without (n = 6) in two Indiana agricultural watersheds: the Shatto Ditch Watershed, which had >60% of croppable acres in winter cover crops, and the Kirkpatrick Ditch Watershed, which had ∼20%. We found that cover crops decreased soil nitrate-N by >50% and that the magnitude of reduction was related to the amount of cover crop biomass. In contrast, cover crops had variable effects on water extractable P and Mehlich III soil test P. Finally, cover crop biomass significantly increased soil N mineralization and nitrification rates, demonstrating that cover crops have the potential to supply bioavailable N to cash crop after termination. Our study showed that widespread implementation of winter cover crops holds considerable promise for reducing nutrient loss and improving soil health. The degree to which these results are generalizable across other systems depends on factors such as climate, soil characteristics, and past and current agronomic practices.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of winter cover crops on soil nutrients in two row‐cropped watersheds in Indiana

et al. 2021

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“…At the eld scale, we expected to see lower DSi concentrations in water from tiles draining elds planted with cover crops versus those without cover crops, particularly during the fall and early winter when cover crops were actively growing. Because cover crops at this study location strongly reduce N loss (Hanrahan et al 2018, Trentman et al 2020 In Review), we predicted water from tile drains in cover cropped elds would have a higher Si:N molar ratio than elds without cover crops. The effect of cover crops on P loss to surface water is variable, and depends, in part, on precipitation patterns (Trentman et al 2020), thus we expected no strong directionality in the response of Si:P molar ratios to winter cover crops.…”

Section: Introductionmentioning

confidence: 99%

Silicon concentrations and stoichiometry in two agricultural watersheds: implications for management and downstream water quality

et al. 2022

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Agriculture alters the biogeochemical cycling of nutrients such as nitrogen (N), phosphorus (P), and silicon (Si) which contributes to the stoichiometric imbalance among these nutrients in aquatic systems. Limitation of Si relative to N and P can facilitate the growth of non-siliceous, potentially harmful, algal taxa which has severe environmental and economic impacts. Planting winter cover crops can retain N and P on the landscape, yet their effect on Si concentrations and stoichiometry is unknown. We analyzed three years of biweekly concentrations and loads of dissolved N, P, and Si from subsurface tile drains and stream water in two agricultural watersheds in northern Indiana. Intra-annual patterns in Si concentrations and stoichiometry showed that cover crop vegetation growth did not reduce in-stream Si concentrations as expected, although, compared to fallow conditions, winter cover crops increased Si:N ratios to conditions more favorable for diatom growth. To assess the risk of non-siliceous algal growth, we calculated a stoichiometric index to quantify biomass growth facilitated by excess N and P relative to Si. Index values showed a divergence between predicted algal growth and what we observed in the streams, indicating other factors in uence algal community composition. The stoichiometric imbalance was more pronounced at high ows, suggesting increased risk of harmful blooms as environmental change increases the frequency and intensity of precipitation in the midwestern U.S. Our data include some of the rst measurements of Si within small agricultural watersheds and provide the groundwork for understanding the role of agriculture on Si export and stoichiometry.

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“…In agricultural watersheds, farmers often implement conservation practices to reduce nutrient losses from their fields to adjacent waterways, and include conservation tillage practices (Allmaras & Dowdy, 1985; Phillips et al, 1980), the two‐stage ditch (Mahl et al, 2015; Roley et al, 2012; Speir et al, 2020), and the planting of winter cover crops in the fallow season (Hanrahan et al, 2018; Kaspar & Singer, 2011; Kladivko et al, 2014; Strock et al, 2004; Trentman et al, 2020). Given the pervasive water quality challenges in agricultural landscapes, effective conservation practices are needed, but the patchwork geomorphology of rivers means an alteration within the watershed at the field scale may be masked when exploring dynamics at the watershed scale (De Jager & Houser, 2012; De Paula, Gerhard, De Barros Ferraz, & Wenger, 2018).…”

Section: Introductionmentioning

confidence: 99%

Water transport pathways influence the propagation of field‐scale NO₃⁻‐N reductions to the watershed scale

Grose

Speir

Thellman

et al. 2022

Hydrological Processes

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Diffuse nutrient runoff from agricultural fields can result in the eutrophication of downstream water bodies, highlighting a need for conservation efforts to reduce dissolved nitrogen (N) and phosphorus (P) loading to adjacent waterways. However, few studies explore how the impacts of field‐scale conservation manifest at the watershed scale. We explored how sources of streamflow and nutrients may influence the magnitude of the impact of conservation practices at a field versus watershed scale at the Shatto ditch watershed (SDW), where the planting of winter cover crops reduced field‐scale nitrate‐N (NO3−‐N) losses from subsurface tile drains by 69%–90%; yet watershed NO3−‐N export only decreased by 13%. To resolve this discrepancy, we used a water budget approach paired with water stable isotope (18O and 2H) analysis to determine the composition of streamflow across seasons, sampling five times from November 2018 to September 2019. While we hypothesized that watershed‐scale patterns in nutrient export were driven by direct groundwater upwelling, we found that this pathway only accounted for 43% of streamflow on average. We also developed a NO3−‐N mass balance for the watershed during our November 2018 sampling; results indicated groundwater upwelling contributed only ~1% of NO3−‐N export at the watershed outlet, while subsurface tile drains contributed the remaining 99%. Specifically, three large county tile drains (with an unknown drainage area and extent of conservation practice implementation) contributed ~69% of the watershed NO3−‐N export, obscuring the impacts of field‐scale conservation in SDW. Our study highlights the importance of cross‐scale analyses to accurately evaluate the effect of conservation given the interactions between sources of streamflow and nutrient loss at the watershed scale.

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Cover crops and precipitation influence soluble reactive phosphorus losses via tile drain discharge in an agricultural watershed

Cited by 11 publications

References 64 publications

Effect of winter cover crops on soil nutrients in two row‐cropped watersheds in Indiana

Effect of winter cover crops on soil nutrients in two row‐cropped watersheds in Indiana

Silicon concentrations and stoichiometry in two agricultural watersheds: implications for management and downstream water quality

Water transport pathways influence the propagation of field‐scale NO₃⁻‐N reductions to the watershed scale

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Cover crops and precipitation influence soluble reactive phosphorus losses via tile drain discharge in an agricultural watershed

Cited by 11 publications

References 64 publications

Effect of winter cover crops on soil nutrients in two row‐cropped watersheds in Indiana

Effect of winter cover crops on soil nutrients in two row‐cropped watersheds in Indiana

Silicon concentrations and stoichiometry in two agricultural watersheds: implications for management and downstream water quality

Water transport pathways influence the propagation of field‐scale NO3−‐N reductions to the watershed scale

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Product

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Water transport pathways influence the propagation of field‐scale NO₃⁻‐N reductions to the watershed scale