Surface Runoff and Tile Drainage Transport of Phosphorus in the Midwestern United States

Abstract

The midwestern United States offers some of the most productive agricultural soils in the world. Given the cool humid climate, much of the region would not be able to support agriculture without subsurface (tile) drainage because high water tables may damage crops and prevent machinery usage in fields at critical times. Although drainage is designed to remove excess soil water as quickly as possible, it can also rapidly transport agrochemicals, including phosphorus (P). This paper illustrates the potential importance of tile drainage for P transport throughout the midwestern United States. Surface runoff and tile drainage from fields in the St. Joseph River Watershed in northeastern Indiana have been monitored since 2008. Although the traditional concept of tile drainage has been that it slowly removes soil matrix flow, peak tile discharge occurred at the same time as peak surface runoff, which demonstrates a strong surface connection through macropore flow. On our research fields, 49% of soluble P and 48% of total P losses occurred via tile discharge. Edge-of-field soluble P and total P areal loads often exceeded watershed-scale areal loadings from the Maumee River, the primary source of nutrients to the western basin of Lake Erie, where algal blooms have been a pervasive problem for the last 10 yr. As farmers, researchers, and policymakers search for treatments to reduce P loading to surface waters, the present work demonstrates that treating only surface runoff may not be sufficient to reach the goal of 41% reduction in P loading for the Lake Erie Basin.

Incorporating Rainfall-Runoff Events into Nitrate-Nitrogen and Phosphorus Load Assessments for Small Tile-Drained Catchments

“…This means that, for both the P-PO 4 and P tot loads, the runoff pattern seems to play in general a more dominant role than land use within the monitored catchments, as discovered also by other studies in similar and different climate and cropping systems [5,9,12,19]. The differences in total runoff in sites with similar geographical conditions were caused most probably by the different areas of their recharge zones [43].…”

“…RMSE expresses the cumulative degree of the relative error of a particular method, related to M6, when both accuracy and precision are taken into account [45]. Accuracy (E) was calculated as a ratio of M6 to M1 to M5 (Equation (8)), and precision was expressed by the standard deviation s of E. The RMSE was then calculated according to Equation (9).…”

“…Intensively managed tile-drained landscapes have been found to have a considerable potential for N and P losses, with regard to different soil conditions and cropping systems, especially during periods with elevated flows [3][4][5][6][7][8][9]. Nutrient concentrations in drainage waters may change rapidly within a rainfall-runoff event due to variable pre-event and event soil/catchment moisture conditions, related soil biogeochemical processes [10][11][12][13], precipitation characteristics, and water flow paths into drainage and with different origin and residence times [14][15][16][17].…”

“…Therefore, it is crucial to develop an approach to identify the processes responsible for the input of pollutants from land to water via tile drainage. To reveal the rapid discharge/concentration changes, describe the related processes, and estimate the true pollutant loads, a proper monitoring programme and appropriate methods for the evaluation of matter fluxes are necessary to support [6,18,38] the design of field to catchment scale mitigation measures for tile drainage or on drained land, as well as when estimating their effects [2,9,22,[38][39][40].…”

Engineering solutions for food-energy-water systems: it is more than engineering

“…For example, no-till conservation has dramatically decreased erosion and associated P loss, although the loss of P in dissolved, more immediately reactive form without the incorporation of applied P can reverse total P gains and be sufficient to stimulate algal blooms (Richards et al 2010;Sharpley and Smith 1994;Tiessen et al 2010). Another trade-off resulting from the cultivation of new lands fueled by corn for bioethanol that is facilitated by tile drainage will directly connect new source areas to stream and ditches, indirectly increasing the potential for P loss (Smith et al 2014(Smith et al , 2015. Clearly, there needs to be a more effective communication and coordination among all involved in agricultural production, policy development, and strategy implementation.…”