Research ArticleRESEARCH SECTION

Dynamics of dissolved reactive phosphorus loss from phosphorus source and sink soils in tile-drained systems

P. Welikhe, S.M. Brouder, J.J. Volenec, M. Gitau and R.F. Turco
Journal of Soil and Water Conservation January 2022, 77 (1) 1-14; DOI: https://doi.org/10.2489/jswc.2022.00012

Article Figures & Data

Figures

  • Figure 1
    Figure 1

    Schematic illustration of the area (Ah) and rotational pattern (R) of a concentration-discharge (C-Q) loop for a drainage event with (a) anti-clockwise rotation, and (b) clockwise rotation. Colors represent loop direction over time.

  • Figure 2
    Figure 2

    A bubble plot of flow-weighted dissolved reactive phosphorus (FWDRP) concentrations (ug L–1), total discharge (L d–1 plot–1), and dissolved reactive phosphorus (DRP) loads (g ha–1) for the selected discharge events between October of 2010 and September of 2013 at the Water Quality Field Station (WQFS). The dashed line marks the concentration (20 ug L–1) above which eutrophication is accelerated (Correll 1999).

  • Figure 3
    Figure 3

    Daily dissolved reactive phosphorus (DRP) flux (kg ha–1) to discharge (mm) relationship presented on a log-log scale for (a) phosphorus source soils and (b) phosphorus sink soils. Exponent (b) and coefficient (a) values are defined by equation 1, and R2 values were determined by linear regression on log transformed dissolved reactive phosphorus flux and discharge values.

  • Figure 4
    Figure 4

    Event dissolved reactive phosphorus (DRP) flux (kg ha–1) to discharge (mm) relationship presented on a log-log scale for (a) phosphorus source soils and (b) phosphorus sink soils. Exponent (b) and coefficient (a) values are defined by equation 1, and R2 values were determined by linear regression on log transformed dissolved reactive phosphorus flux and discharge values.

  • Figure 5
    Figure 5

    (a) A proposed conceptual model illustrating dissolved reactive phosphorus (DRP) loss in tile drained fields from phosphorus (P) source soils where (i) discharge at the start of the event when P rich preferential flow (event water) from the surface rapidly flows to tile drains, (ii) discharge during the event when P rich event water is mixed with P poor water from the soil matrix and shallow groundwater, resulting in an overall dilution, and (iii) when the discharge recedes, contributions from soil matrix and shallow groundwater are absent, event water with high P concentrations continues. (b) A proposed conceptual model illustrating DRP loss in tile drained fields from P sink soils where (i) discharge at the start of the event when P poor preferential flow (event water) from the surface rapidly flows to tile drains, (ii) discharge during the event when P poor waters (preferential, matrix, and shallow groundwater) mix, and (iii) when soil matrix and shallow groundwater recede, event water with low P concentrations continues.

  • Figure 6
    Figure 6

    Plot of relative change in solute concentrations (ΔCnew [%]) versus change in rotational patterns (ΔR [%]) for the C-Q hysteresis loops of dissolved reactive phosphorus (DRP). The i, j, and k terms in the plot labels correspond to ith season (winter [W], spring [Sp], summer [Su], and fall [F]) in a water year (2011, 2012, and 2013), the jth plot at the Water Quality Field Station (P10, P11, P12, P26, P30, P32, P43, and P44), and the kth discharge event for the specified plot. Supplementary table S1 provides detailed information on discharge events. Illustrations of the typical C-Q relationships (C, dashed blue line; Q, continuous brown line) are presented for each of the regions A through D of the ΔCnew (%) versus ΔR plot. A few events in phosphorus source soils showed clockwise hysteresis.

Tables

  • Table 1

    A brief description of current no-till treatments at the Water Quality Field Station (abbreviations and year of establishment [yr.est.]), any previous treatments (cropping systems and nitrogen [N] rates applied to maize) dating back to 1997, and phosphorus [P], N, and tillage management.

    Table 1
  • Table 2

    Soil Phosphorus Storage Capacity (SPSC) and Soil Test Phosphorus (STP) for surface soils (20 cm) reported in Welikhe et al. (2020a). Negative and positive SPSC values are associated with P source and P sink soils, respectively. Years 2011, 2012, and 2013 are water years, e.g., 2011 water year begins on October 1, 2010, and ends on September 30, 2011. Refer to table 1 for descripion of treatments.

    Table 2
  • Table 3

    The number of days with missing flow data for tiles in the study plots. The percentage of number of days with missing data per water year is presented parenthetically.

    Table 3
  • Table 4

    Annual (water year) dissolved reactive phosphorus (DRP) loads and flow-weighted dissolved reactive phosphorus (FDRP) concentrations in tile discharge. Plots with negative Soil Phosphorus Storage Capacity values (phosphorus source soils) are in bold. Concentrations above which eutrophication is accelerated i.e., > 20 ug P L–1 (Correll 1999) are italicized. Refer to table 1 for description of treatments.

    Table 4
  • Table 5

    Pearson correlation matrix between general discharge event characteristics and the ΔR (%) and ΔC (%) parameters (combined data for phosphorus [P] source and P sink soils).

    Table 5

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Dynamics of dissolved reactive phosphorus loss from phosphorus source and sink soils in tile-drained systems
P. Welikhe, S.M. Brouder, J.J. Volenec, M. Gitau, R.F. Turco
Journal of Soil and Water Conservation Jan 2022, 77 (1) 1-14; DOI: 10.2489/jswc.2022.00012
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