Variable response to phosphorus mitigation measures across the nutrient transfer continuum in a dairy grassland catchment

Murphy, Paul; Mellander, Per‐Erik; Melland, Alice R.; Buckley, Cathal; Shore, Mairead; Shortle, G.; Wall, David P.; Treacy, M. F.; Shine, O.; Mechan, S.; Jordan, Phillip

doi:10.1016/j.agee.2015.04.008

Cited by 45 publications

(29 citation statements)

References 38 publications

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“…Time lags of 15-20 years beyond the initial WFD deadline of 2015 are projected for P in Irish surface soils to reach the optimum index [35]. Promisingly, the soil P index in the well-drained grassland is trending towards an agronomic optimum thanks to improved nutrient use efficacy supported by field-scale soil sampling and site-specific nutrient recommendations [32,36]. This trend should decrease P entering the subsurface pathway and curtail future leaching losses, subject to a biogeochemical and hydrological time lag.…”

Section: Well-drained Grasslandmentioning

confidence: 99%

Sources and Mechanisms of Low-Flow River Phosphorus Elevations: A Repeated Synoptic Survey Approach

Vero

Daly

McDonald

et al. 2019

Water

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High-resolution water quality monitoring indicates recurring elevation of stream phosphorus concentrations during low-flow periods. These increased concentrations may exceed Water Framework Directive (WFD) environmental quality standards during ecologically sensitive periods. The objective of this research was to identify source, mobilization, and pathway factors controlling in-stream total reactive phosphorus (TRP) concentrations during low-flow periods. Synoptic surveys were conducted in three agricultural catchments during spring, summer, and autumn. Up to 50 water samples were obtained across each watercourse per sampling round. Samples were analysed for TRP and total phosphorus (TP), along with supplementary parameters (temperature, conductivity, dissolved oxygen, and oxidation reduction potential). Bed sediment was analysed at a subset of locations for Mehlich P, Al, Ca, and Fe. The greatest percentages of water sampling points exceeding WFD threshold of 0.035 mg L −1 TRP occurred during summer (57%, 11%, and 71% for well-drained, well-drained arable, and poorly drained grassland catchments, respectively). These percentages declined during autumn but did not return to spring concentrations, as winter flushing had not yet occurred. Different controls were elucidated for each catchment: diffuse transport through groundwater and lack of dilution in the well-drained grassland, in-stream mobilization in the well-drained arable, and a combination of point sources and cumulative loading in the poorly drained grassland. Diversity in controlling factors necessitates investigative protocols beyond low-spatial and temporal resolution water sampling and must incorporate both repeated survey and complementary understanding of sediment chemistry and anthropogenic phosphorus sources. Despite similarities in elevation of P at low-flow, catchments will require custom solutions depending on their typology, and both legislative deadlines and target baselines standards must acknowledge these inherent differences.

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Section: Well-drained Grasslandmentioning

confidence: 99%

Sources and Mechanisms of Low-Flow River Phosphorus Elevations: A Repeated Synoptic Survey Approach

Vero

Daly

McDonald

et al. 2019

Water

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“…Large input of P fertilizer or manure application saturated the soil P sorption capacity, inducing a large rate of loss, especially when the farm is managed using flood irrigation or fertilized before heavy rain (Sinaj et al, 2002;Toor et al, 2005). Positive P balance due to continuous P fertilization would induce the risk of nutrient losses to the surface and groundwater (e.g., eutrophication in river, lake and ocean) (Haygarth et al, 1998;McDowell and Sharpley, 2004;Murphy et al, 2015).…”

Section: Managed Grasslandsmentioning

confidence: 99%

“…Although rare, negative P balance also occurred in managed grasslands due to, for examples high stocking rate and animal production while placing restriction on fertilizer application rate and farm-gate imports (Murphy et al, 2015). While these efforts were initially conducted to increase P use efficiency and decrease P surplus, over time, negative P balance could decrease the sustainability of grassland ecosystem productivity.…”

Section: Managed Grasslandsmentioning

confidence: 99%

“…Surface runoff is another main output pathway of P caused by the erosion of TPP, desorption of labile P, and dissolution of non-labile P from surface soil Murphy et al, 2015). Excessive mineral and manure application on managed grassland soils often leads to P-enriched surface soils (and subsequent elevated soil test P, STP), which are very susceptible to runoff losses (Mittelstet et al, 2011;Turtola and Jaakkola, 1995).…”

Section: Surface Runoffmentioning

confidence: 99%

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Soil phosphorus budget in global grasslands and implications for management

Zhou

Daryanto

Xin

et al. 2017

Journal of Arid Environments

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Grasslands, accounting for one third of the world terrestrial land surface, are important in determining phosphorus (P) cycle at a global scale. Understanding the impacts of management on P inputs and outputs in grassland ecosystem is crucial in environmental management since a large amount of P is transported through rivers and groundwater and detained by sea reservoir every year. To better understand the P cycle in global grasslands, we mapped the distribution of different grassland types around the world and calculated the corresponding P inputs and outputs for each grassland type using data from the literature. The distribution map of P input and output revealed a nonequilibrium condition in many grassland ecosystems, with: (i) a greater extent of inputs than outputs in most managed grasslands, but (ii) a more similar inputs and outputs in the majority of natural grasslands. Based on the mass balance between P input and output, we developed a framework to achieve sustainable P management in grasslands and discussed the measures targeting a more balanced P budget. Greater challenge is usually found in heavily-managed than natural grasslands to establish the optimum amount of P for grass and livestock production while minimizing the adverse impacts on surface waters. This study provided a comprehensive assessment of P budget in global grasslands and such information will be critical in determining the appropriate P management measures for various grassland types across the globe.

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“…The data originated from three river catchment observatories in Ireland that have different hydrological responses to rainfall and thus cover a range of potential monitoring scenarios. These datasets have previously provided important insights into agrienvironmental policies (Murphy et al 2015;Shore et al 2016) and nutrient hydrological pathway dynamics and seasonality (Jordan et al 2012;Mellander et al 2012;Dupas et al 2017). The specific objectives of the present study were to (1) assess the fitness of different parametric models in reproducing the highfrequency data and (2) compare the performances of these and alternative statistical models in estimating water quality statistics and determining the physicochemical status of the three study rivers.…”

Section: Introductionmentioning

confidence: 99%

Benchmarking inference methods for water quality monitoring and status classification

Jung

Senf

Jordan

et al. 2020

Environ Monit Assess

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River water quality monitoring at limited temporal resolution can lead to imprecise and inaccurate classification of physicochemical status due to sampling error. Bayesian inference allows for the quantification of this uncertainty, which can assist decision-making. However, implicit assumptions of Bayesian methods can cause further uncertainty in the uncertainty quantification, so-called second-order uncertainty. In this study, and for the first time, we rigorously assessed this second-order uncertainty for inference of common water quality statistics (mean and 95th percentile) based on sub-sampling high-frequency (hourly) total reactive phosphorus (TRP) concentration data from three watersheds. The statistics were inferred with the low-resolution sub-samples using the Bayesian lognormal distribution and bootstrap, frequentist t test, and face-value approach and were compared with those of the high-frequency data as benchmarks. The t test exhibited a high risk of bias in estimating the water quality statistics of interest and corresponding physicochemical status (up to 99% of sub-samples). The Bayesian lognormal model provided a good fit to the high-frequency TRP concentration data and the least biased classification of physicochemical status (< 5% of sub-samples). Our results suggest wide applicability of Bayesian inference for water quality status classification, a new approach for regulatory practice that provides uncertainty information about water quality monitoring and regulatory classification with reduced bias compared to frequentist approaches. Furthermore, the study elucidates sizeable second-order uncertainty due to the choice of statistical model, which could be quantified based on the high-frequency data.

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Variable response to phosphorus mitigation measures across the nutrient transfer continuum in a dairy grassland catchment

Cited by 45 publications

References 38 publications

Sources and Mechanisms of Low-Flow River Phosphorus Elevations: A Repeated Synoptic Survey Approach

Sources and Mechanisms of Low-Flow River Phosphorus Elevations: A Repeated Synoptic Survey Approach

Soil phosphorus budget in global grasslands and implications for management

Benchmarking inference methods for water quality monitoring and status classification

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