Field scale phosphorus balances and legacy soil pressures in mixed-land use catchments

McDonald, Noeleen; Wall, David P.; Mellander, Per‐Erik; Buckley, Cathal; Shore, Mairead; Shortle, G.; Leach, Simon; Burgess, Edward; O'Connell, Tina; Jordan, Phil

doi:10.1016/j.agee.2018.12.014

Cited by 25 publications

(19 citation statements)

References 28 publications

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“…These values were below the 11.7 change point, which has been identified as a threshold where P is likely to be strongly fixed/released [37]. This indicates that P is not strongly attenuated in the stream sediments and may be liable to release under suitable stream conditions (temperature, pH [32,38]). Hence, the processes of in-stream mobilization are unlikely to contribute to low-flow P concentrations in water samples in this catchment.…”

Section: Catchment-specific Controls and Implications For Managementmentioning

confidence: 92%

“…For the purposes of the survey, low-flow was considered as the 70th percentile of discharge and no antecedent rainfall in the preceding 48 h. Sampling dates and conditions are shown in Table 2. Sampling locations were predetermined based on visual inspection of the catchments (including access to the stream, livestock drinking points, and field drains), targeted distribution of samples across the entire watercourse, and particular areas of interest determined from previous studies at these sites [11,15,31,32]. Mainstream sampling points begin with the letter M, tributary points with T, and ditches with D. A target of 50 samples per catchment was determined, permitting a sample density of about 5-6 samples per km stream length.…”

Section: Synoptic Surveymentioning

confidence: 99%

“…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%

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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: Catchment-specific Controls and Implications For Managementmentioning

confidence: 92%

Section: Synoptic Surveymentioning

confidence: 99%

Section: Well-drained Grasslandmentioning

confidence: 99%

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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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“…A more likely reason for the absence of trends were that a small proportion of samples that came from the same farm in the dataset (<5%). Coupled with on-farm spatial variation in P, which can be as high as 100% in many grassland farms (McDonald et al, 2019), the likelihood of detecting a change associated with repeated measures is probably low. Trends within a land use such as dairy farms may not occur as New Zealand dairy farms are largely able to balance P inputs and outputs.…”

Section: State and Trends In Olsen P Concentrationsmentioning

confidence: 99%

The Ability to Reduce Soil Legacy Phosphorus at a Country Scale

McDowell

Dodd

Pletnyakov

et al. 2020

Front. Environ. Sci.

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The build-up of soil phosphorus (P) beyond plant requirements can lead to a longterm legacy of P losses that could impair surface water quality. Using a database of ∼4,50,000 samples collected from 2001-2015 we report the level of soil P enrichment by soil type, land use and region and the time it would take for Olsen P to decline to agronomic targets (20-0 mg L −1 ) if P fertilizer was stopped. We also modeled the time it would take for water extractable P (WEP), an indicator of P losses in surface runoff, to decline to an environmental target (0.02 mg L −1 ). Some 63% of the samples were enriched beyond agronomic targets. The area-weighted median time to reach the agronomic target was predicted to occur within a year for 75% of samples but varied up to 11.8 years in some land uses. However, the area-weighted time to reach an environmental target was 26-55 years for the 50th and 75th percentile of areas. This indicates that while an agronomic target can be easily met, additional strategies other than stopping P fertilizer inputs are required to meet an environmental target.

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“…The distance between the two catchments is ~20 km. The catchments are characterised in detail in Fealy et al (2010), Jordan et al (2012), Wall et al (2011) and McDonald et al (2019) and summarised here. The well-drained arable catchment (1,120 ha) consists of generally well-drained brown earth soils (Cambisols) (88%), with lesser areas including gleyic brown earths, brown podzolics and groundwater gleys.…”

Section: Study Sitesmentioning

confidence: 99%

The Beast from the East: impact of an atypical cold weather event on hydrology and nutrient dynamics in two Irish catchments

Vero

McDonald

McGrath

et al. 2020

Irish Journal of Agricultural and Food Research

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A historic lack of continuous stream nutrient monitoring at the catchment scale limits understanding of the effects of snowstorms. The most significant snowstorm since 1985, nicknamed “the Beast from the East”, occurred in February–March 2018. High-frequency stream outlet monitoring in two close but hydrologically and agriculturally contrasting catchments (<1,200 ha) captured phosphorus (total and reactive), total oxygenated nitrogen (TON), temperature and discharge dynamics during and after the event. The grassland catchment consists of poorly drained gley soils and exhibits overland flow pathways, while the arable catchment consists of well-drained brown earths and is dominated by subsurface pathways. Nitrate (NO 3 -N) concentrations were initially elevated (3.50 and 7.89 mg/L for poorly drained grassland and well-drained arable catchments, respectively) before becoming diluted by meltwater. Total reactive phosphorus (TRP) displayed a distal (anti-clockwise) concentration-discharge hysteresis in the poorly drained grassland catchment suggesting low mobilisation from the soil. Conversely, the well-drained arable catchment displayed proximal (clockwise) hysteresis, indicative of the mobilisation from stream and bank sediment. These relatively infrequent snow events behave similarly to heavy rainfall as regards nutrient losses, albeit subject to a time-lag induced by the speed of snowmelt and the soil moisture deficit (SMD) prior to snowfall. Antecedent land management is crucial to mitigate risk. The current absence of records and analyses of catchment response, particularly nutrient dynamics, to atypical cold weather events in Ireland limits understanding of their effects on water quality. The present study provides the first such baseline information from which land management strategies and the implications for attaining environmental targets can be explored.

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Field scale phosphorus balances and legacy soil pressures in mixed-land use catchments

Cited by 25 publications

References 28 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

The Ability to Reduce Soil Legacy Phosphorus at a Country Scale

The Beast from the East: impact of an atypical cold weather event on hydrology and nutrient dynamics in two Irish catchments

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