Impact of slurry application method on phosphorus loss in runoff from grassland soils during periods of high soil moisture content

peer-reviewedPrevious studies have reported that the trailing shoe application technique reduces phosphorus (P) in the runoff postslurry application when compared to the traditional splash-plate application technique. However, the effectiveness of the trailing-shoe technique as a means of reducing P losses has not been evaluated when slurry is applied during periods of high soil moisture levels and lower herbage covers. To address this issue, three treatments were examined in a 3 × 4 factorial design split-plot experiment, with treatments comprising three slurry treatments: control (no slurry), splashplate and trailing-shoe, and four slurry application dates: 7 December, 18 January, 1 March and 10 April. Dairy cow slurry was applied at a rate of 20 m3/ha, while simulated runoff was generated 2, 9 and 16 days later and analysed for a range of P fractions. Dissolved reactive P concentrations in runoff at day two was 41% lower when slurry was applied using the trailing-shoe technique, compared to the splash-plate technique (P < 0.05). In addition, P concentrations in runoff were higher (P < 0.05) from slurry applied in December and March compared to slurry applied in January or April, coinciding with periods of higher soil moisture contents. While the latter highlights that ‘calendar’-based non-spreading periods might not always achieve the desired consequences, the study demonstrated that further field-scale investigations into the trailing shoe as a mitigation measure to reduced P loss from agricultural soils is warranted

Approaches to herbicide (MCPA) pollution mitigation in drinking water source catchments using enhanced space and time monitoring

Publication history: Accepted - 30 September 2020; Published online - 8 October 2020Freshwater occurrences of the selective acid herbicide 2-methyl-4-chloro-phenoxyacetic acid (MCPA) are an ongoing regulatory and financial issue for water utility industries as the number and magnitude of detections increase, particularly in surface water catchments. Assessments for mitigating pesticide pollution in catchments used as drinking water sources require a combination of catchment-based and water treatment solutions, but approaches are limited by a lack of empirical data. In this study, an enhanced spatial (11 locations) and temporal (7-hourly to daily sampling) monitoring approach was employed to address these issues in an exemplar surface water source catchment (384 km2). The spatial sampling revealed that MCPA was widespread, with occurrences above the 0.1 μg L−1 threshold for a single pesticide being highly positively correlated to sub-catchments with higher proportions of ‘Improved Grassland’ land use (r = 0.84). These data provide a strong foundation for targeting catchment-based mitigation solutions and also add to the debate on the ecosystems services provided by such catchments. Additionally, of the 999 temporal samples taken over 12 months from the catchment outlet, 25% were above the drinking water threshold of 0.1 μg L−1. This prevalence of high concentrations presents costly problems for source water treatment. Using these data, abstraction shutdowns were simulated for five scenarios using hydrometeorological data to explore the potential to avoid intake of high MCPA concentrations. The scenarios stopped abstraction for 4.2–9.3% of the April–October period and reduced intake of water containing over 0.1 μg L−1 of MCPA by 16–31%. This represents an important development for real-time proxy assessments for water abstraction in the absence of more direct pesticide monitoring data.This work was funded by the Source to Tap project (project reference IVA5018 – www.sourcetotap.eu). The Source to Tap project is supported by the European Union's INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB)

Evaluation of Chemcatcher® passive samplers for pesticide monitoring using high-frequency catchment scale data

Publication history: Accepted - 13 September 2022; Published online - 30 September 2022Passive samplers (PS) have been proposed as an enhanced water quality monitoring solution in rivers, but their performance against high-frequency data over the longer term has not been widely explored. This study compared the performance of Chemcatcher® passive sampling (PS) devices with high-frequency sampling (HFS: 7-hourly to daily) in two dynamic rivers over 16 months. The evaluation was based on the acid herbicides MCPA (2-methyl-4-chlorophenoxyacetic acid), mecoprop-P, fluroxypyr and triclopyr. The impact of river discharge parameters on Chemcatcher® device performance was also explored. Mixed effects modelling showed that time-weighted mean concentration (TWMC) and flow-weighted mean concentration (FWMC) values obtained by the HFS approach were both significantly higher (p 0.05). There was little indication that river flow parameters altered PS performance—some minor effects were not significant or consistent. Despite this, the PS recovery of very low concentrations indicated that Chemcatcher® devices may be used to evaluate the presence/absence and magnitude of acid herbicides in hydrologically dynamic rivers in synoptic type surveys where space and time coverage is required. However, a period of calibration of the devices in each river would be necessary if they were intended to provide a quantitative review of pesticide concentration as compared with HFS approaches.This work was funded in part by the Source to Tap project (project reference IVA5018 – http://www.sourcetotap.eu), supported by the European Union’s INTERREG VA Programme which is managed by the Special EU Programmes Body (SEUPB). The work was also part-funded by the FAIRWAY project (project reference 727984 - http://www.fair way-project.eu/). supported by the European Union’s HORIZON 2020 Programme

Pathways for nutrient loss to water with emphasis on phosphorus

Teagasc wishes to acknowledge the support of the Environmental Research Technological Development and Innovation (ERTDI) Programme under the Productive Sector Operational Programme which was financed by the Irish Government under the National Development Plan 2000-2006.End of project reportThe main objective of this project was to study phosphorus (P) loss from agricultural land under a range of conditions in Ireland, to quantify the main factors influencing losses and make recommendations on ways to reduce these losses. This report is a synthesis of the main conclusions and recommendations from the results of the studies. The final reports from the individual sub-projects in this project are available from the EPA (www.epa.ie).Environmental Protection Agenc

Guiding phosphorus stewardship for multiple ecosystem services

The essential role of phosphorus (P) for agriculture and its impact on water quality has received decades of research attention. However, the benefits of sustainable P use and management for society due to its downstream impacts on multiple ecosystem services are rarely acknowledged. We propose a conceptual framework—the “phosphorus-ecosystem services cascade” (PESC)—to integrate the key ecosystem processes and functions that moderate the relationship between P released to the environment from human actions and ecosystem services at distinct spatial and temporal scales. Indirect pathways in the cascade via soil and aquatic processes link anthropogenic P to biodiversity and multiple services, including recreation, drinking water provision, and fisheries. As anthropogenic P cascades through catchments, it often shifts from a subsidy to a stressor of ecosystem services. Phosphorus stewardship can have emergent ecosystem service co-benefits due to synergies with other societal or management goals (e.g., recycling of livestock manures and organic wastes could impact soil carbon storage). Applying the PESC framework, we identify key research priorities to align P stewardship with the management of multiple ecosystem services, such as incorporating additional services into agri-environmental P indices, assessing how widespread recycling of organic P sources could differentially impact agricultural yields and water quality, and accounting for shifting baselines in P stewardship due to climate change. Ultimately, P impacts depend on site-specific agricultural and biogeophysical contexts, so greater precision in targeting stewardship strategies to specific locations would help to optimize for ecosystem services and to more effectively internalize the downstream costs of farm nutrient management

Lough Melvin: Developing cost-effective measures to prevent phosphorus enrichment of a unique aquatic habitat

peer-reviewedLough Melvin, located on the border of Leitrim (Republic of Ireland) and Fermanagh (Northern Ireland), is unique among Irish lakes, supporting a fish community typical of a natural post-glacial salmonid lake, and has been designated as a Special Area of Conservation (SAC). The biodiversity of the lake is vulnerable to changes in water quality resulting from eutrophication, and over the last 15 years, phosphorus (P) concentrations have increased to the upper range of mesotrophic classification. Agriculture has been reported as one of the main contributors of P loadings to the lake, which poses an apparent paradox in light of the low-intensity nature of farming practices in the catchment. The objectives of the project reported on here were to identify the dominant P pressure and pathway risks governing P loss in the catchment, and to evaluate and select potential mitigation measures, based on an assessment of cost-effectiveness and farmer preference. Throughout this project, we employed an explicitly participatory approach, with farmer stakeholders inputting directly into the identification and evaluation of mitigation measures. We identified risks on 50 survey farms by using the modified P Ranking Scheme. A suite of 25 potential mitigation strategies was identified from the literature and on-farm interviews. For each measure, we derived the order of magnitude of potential costs, impact, and cost-effectiveness, and measures were preferentially ranked by 25 participating farmers. The resulting ranking of measures showed that support for nutrient management planning and soil analysis was the most cost-effective and popular measure aimed at reducing P pressures in the long term, while installation of sediment traps in drainage ditches was the most cost-effective and popular measure aimed at reducing P transport vectors in the short term. We demonstrate that through this careful evaluation and selection of mitigation measures, over 50% of potential total reduction in P loss can be achieved at c. 5% of potential total cost. In addition, we show that measures commonly proposed to mitigate against “high-visibility risks” are not necessarily cost-effective or acceptable to farmer stakeholders. The results of this study are specific to the biophysical environment and farming context of the Lough Melvin catchment, however, we suggest that the approach taken in our project may be used as a template for the formulation of regional catchment management plans, such as the draft river basin district management plans required under the Water Framework Directive.This project was part of the Lough Melvin Nutrient Reduction Programme, administered by the Northern Regional Fisheries Board (Republic of Ireland) and funded by INTERREG IIIa, administered by the Environment and Heritage Service (Northern Ireland)

Good water status: The integration of sustainable grassland production and water resources in Ireland

Peer-reviewedThe challenge for sustainable grassland production is to integrate economically profitable farming systems with environmental protection. The Water Framework Directive aims to attain at least “good status” for all waters by 2015, to be achieved through the introduction of measures across all sectors of society. Historically, the impact of grassland agriculture on water quality was investigated in isolation. More recently it has been highlighted that water quality and other environmental impacts such as greenhouse gas emissions must be considered in an integrated manner. Catchment hydrology is critical to understanding the drivers behind nutrient transport to surface water and groundwaters. Flashy catchments are more susceptible to phosphorus, sediment and ammonium loss, whereas contrastingly baseflow dominated catchments are more susceptible to nitrate transport. Understanding catchment hydrology enables the targeting of measures for the mitigation of diffuse agricultural contaminants. This increased understanding can also be used to support extended deadlines for the achievement of good status. This paper reviews the potential effects of grassland agriculture on water quantity and the transport of pesticides and nutrients to water in the context of achieving good status for all waters by 2015 under the Water Framework Directive

Agriculture and Eutrophication: Where Do We Go from Here?

The eutrophication of surface waters has become an endemic global problem. Nutrient loadings from agriculture are a major driver, but it remains very unclear what level of on-farm controls are necessary or can be justified to achieve water quality improvements. In this review article, we use the UK as an example of societies’ multiple stressors on water quality to explore the uncertainties and challenges in achieving a sustainable balance between useable water resources, diverse aquatic ecosystems and a viable agriculture. Our analysis shows that nutrient loss from agriculture is a challenging issue if farm productivity and profitability is to be maintained and increased. Legacy stores of nitrogen (N) and phosphorus (P) in catchments may be sufficient to sustain algal blooms and murky waters for decades to come and more innovation is needed to drawdown and recover these nutrients. Agriculture’s impact on eutrophication risk may also be overestimated in many catchments, and more accurate accounting of sources, their bioavailabilities and lag times is needed to direct proportioned mitigation efforts more effectively. Best practice farms may still be leaky and incompatible with good water quality in high-risk areas requiring some prioritization of society goals. All sectors of society must clearly use N and P more efficiently to develop long-term sustainable solutions to this complex issue and nutrient reduction strategies should take account of the whole catchment-to-coast continuum. However, the right balance of local interventions (including additional biophysical controls) will need to be highly site specific and better informed by research that unravels the linkages between sustainable farming practices, patterns of nutrient delivery, biological response and recovery trajectories in different types of waterbodies

A new direction for tackling phosphorus inefficiency in the UK food system

The UK food system is reliant on imported phosphorus (P) to meet food production demand, though inefficient use and poor stewardship means P is currently accumulating in agricultural soils, wasted or lost with detrimental impacts on aquatic environments. This study presents the results of a detailed P Substance Flow Analysis for the UK food system in 2018, developed in collaboration with industry and government, with the key objective of highlighting priority areas for system interventions to improve the sustainability and resilience of P use in the UK food system. In 2018 the UK food system imported 174.6 Gg P, producing food and exportable commodities containing 74.3 Gg P, a P efficiency of only 43%. Three key system hotspots for P inefficiency were identified: Agricultural soil surplus and accumulation (89.2 Gg P), loss to aquatic environments (26.2 Gg P), and waste disposal to landfill and construction (21.8 Gg P). Greatest soil P accumulation occurred in grassland agriculture (85% of total accumulation), driven by loadings of livestock manures. Waste water treatment (12.5 Gg P) and agriculture (8.38 Gg P) account for most P lost to water, and incineration ashes from food system waste (20.3 Gg P) accounted for nearly all P lost to landfill and construction. New strategies and policy to improve the handling and recovery of P from manures, biosolids and food system waste are therefore necessary to improve system P efficiency and reduce P accumulation and losses, though critically, only if they effectively replace imported mineral P fertilisers