The Phosphorus Indicators Tool: a simple model of diffuse P loss from agricultural land to water

Field drainage, in the form of permanently installed pipes or temporary mole drains, is extensively used in Britain to reduce the incidence of waterlogging, and increase the length of the grazing season. Whereas the installation of artificial drains significantly improves the structural stability of the soil, water quality in recipient streams may be adversely affected by the accelerated rate of nutrient transport, and the circumvention of critical storage areas such as buffer zones. This research investigates the importance of phosphorus (P) loss in tile drainage for a mixed agricultural catchment (120 ha) in the UK. Phosphorus concentrations in drain discharge were low (<100 μg Total P l−1) and stable during base-flow periods (<0.5 1 min−1), and generally lower than in the receiving stream. In contrast, temporary (hours) elevated P peaks exceeding 1 mg Total P l−1 were measured in drain-flow during high discharge periods (>10 1 min−1). Large sediment-associated particulate P losses were measured during the first major drain-flow events of the autumn. Field drains are evidently effective conduits for P export from agricultural catchments. Recommendations for controlling P loss from diffuse agricultural sources are therefore critically dependent on a better understanding of surface and subsurface transport pathways.

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Phosphorus loss assessment tools: a review of underlying concepts and applicability in cold climates

Environmental Science and Pollution Research ◽

10.1007/s11356-019-06800-9 ◽

2019 ◽

Vol 27 (4) ◽

pp. 3794-3802

Author(s):

Reza Habibiandehkordi ◽

D. Keith Reid ◽

Pradeep K. Goel ◽

Asim Biswas

Keyword(s):

Surface Waters ◽

Agricultural Land ◽

Assessment Tools ◽

Optimal Placement ◽

Quality Data ◽

Cold Climates ◽

Loss Assessment ◽

Water Quality Data ◽

Phosphorus Loss ◽

P Loss

AbstractIdentifying critical source areas (CSAs) of a watershed by phosphorus (P) loss assessment tools is essential for optimal placement of beneficial management practices (BMPs) to address diffuse P pollution. However, lack of significant progress in tackling diffuse P pollution could be, in part, associated with inefficacy of P loss assessment tools for accurately identifying CSAs. Phosphorus loss assessment tools have been developed to simulate P loss from the landscape where runoff is mainly driven by rainfall events. Therefore, they may underperform in cold climates where the land is often frozen during winter and runoff is dominated by snowmelt. This paper (i) reviews the strengths and weaknesses of current P loss assessment tools and their underlying assumptions in simulating soil P dynamics and P transfer to runoff, and (ii) highlights a number of challenges associated with modeling P transfer from agricultural land to surface waters in cold climates. Current P loss assessment tools do not appear to fully represent hydrological and biogeochemical processes responsible for P loss from CSAs, particularly in cold climates. Effort should be made to develop P loss assessment tools that are capable of considering P dynamics through the landscape as a result of abiotic perturbations that are common in cold climates, predicting runoff and P movement over frozen/partially frozen soils, and considering material-P connectivity between landscape and surface waters. Evaluating P loss assessment tools with water quality data is necessary to ensure such modifications result in improved identification of CSAs.

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Phosphorus accumulation in Canadian agricultural soils over 30 yr

Canadian Journal of Soil Science ◽

10.1139/cjss-2019-0023 ◽

2019 ◽

Vol 99 (4) ◽

pp. 520-532

Author(s):

Keith Reid ◽

Kimberley D. Schneider

Keyword(s):

Prince Edward Island ◽

Agricultural Land ◽

Agricultural Soils ◽

P Loss ◽

Livestock Density ◽

Phosphorus Accumulation ◽

Soil Test P ◽

P Balance ◽

Key Driver ◽

Significant Regression

Phosphorus (P) loss to freshwater is a key driver of eutrophication, and understanding the scale and spatial distribution of potential P sources is a key pre-requisite for implementing policies for P management to minimize environmental impacts. Soil test P (STP) is a useful indicator of the accumulation of P in soils, but these data are not readily available for most agricultural land in Canada, so the cumulative P balance (P inputs as manure or fertilizer minus removal of P in crops) is calculated as a proxy for this value. Cumulative P balance is an important calculation within the indicator of risk of water contamination by P, so allocations of manure and fertilizer P to cropland were updated within the calculation of P balance, and for Ontario, data from 1961 to 1980 were added to account for P applications during that period. The STP concentrations were calculated from the resulting cumulative P balances. When compared with reported STP concentrations, the predicted concentrations showed a statistically significant regression at the national (R2 = 78%) and provincial scale (Ontario, R2 = 36%; Prince Edward Island, R2 = 36%; Manitoba, R2 = 72%; British Columbia, R2 = 40%). There was significant variation in the cumulative P balance across Canada, with the highest values corresponding with areas of high livestock density, whereas large zones of P deficit were detected across the Prairies.

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Evaluating measures to control the impact of agricultural phosphorus on water quality

Water Science & Technology ◽

10.2166/wst.1999.0541 ◽

1999 ◽

Vol 39 (12) ◽

pp. 149-155 ◽

Cited By ~ 18

Author(s):

Louise Heathwaite ◽

Andrew Sharpley

Keyword(s):

Surface Runoff ◽

Agricultural Land ◽

Point Sources ◽

Control Measures ◽

Scale Model ◽

Control Mechanisms ◽

P Loss ◽

Transport Control ◽

The Impact ◽

Field Approaches

Current issues in phosphorus loss from non-point sources are reviewed. The need to balance both source and transport control mechanisms in field approaches aimed at controlling P loss from agricultural land is explored. Other control measures such as P source manipulation are evaluated. A case is made for integrating work on P loss at various research scales, from plot to hillslope to catchment, and a simple field-scale model to evaluate the factors controlling P loss in surface runoff is presented.

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