Soil and water management: opportunities to mitigate nutrient losses to surface waters in the Northern Great Plains

Abstract

The Northern Great Plains is a key region to global food production. It is also a region of water stress that includes poor water quality associated with high concentrations of nutrients. Agricultural nitrogen and phosphorus loads to surface waters need to be reduced, yet the unique characteristics of this environment create challenges. The biophysical reality of the Northern Great Plains is one where snowmelt is the major period of nutrient transport, and where nutrients are exported predominantly in dissolved form. This limits the efficacy of many beneficial management practices (BMPs) commonly used in other regions and necessitates place-based solutions. We discuss soil and water management BMPs through a regional lens—first understanding key aspects of hydrology and hydrochemistry affecting BMP efficacy, then discussing the merits of different BMPs for nutrient control. We recommend continued efforts to “keep water on the land” via wetlands and reservoirs. Adoption and expansion of reduced tillage and perennial forage may have contributed to current nutrient problems, but both practices have other environmental and agronomic benefits. The expansion of tile and surface drainage in the Northern Great Plains raises urgent questions about effects on nutrient export and options to mitigate drainage effects. Riparian vegetation is unlikely to significantly aid in nutrient retention, but when viewed against an alternative of extending cultivation and fertilization to the waters’ edge, the continued support of buffer strip management and refinement of best practices (e.g., harvesting vegetation) is merited. While the hydrology of the Northern Great Plains creates many challenges for mitigating nutrient losses, it also creates unique opportunities. For example, relocating winter bale-grazing to areas with low hydrologic connectivity should reduce loadings. Managing nutrient applications must be at the center of efforts to mitigate eutrophication. In this region, ensuring nutrients are not applied during hydrologically sensitive periods such as late autumn, on snow, or when soils are frozen will yield benefits. Working to ensure nutrient inputs are balanced with crop demands is crucial in all landscapes. Ultimately, a targeted approach to BMP implementation is required, and this must consider the agronomic and economic context but also the biophysical reality.

Landscape Controls on Nutrient Export during Snowmelt and an Extreme Rainfall Runoff Event in Northern Agricultural Watersheds

“…The eutrophication of aquatic ecosystems is a significant environmental problem within the northern Great Plains (Baulch et al, 2019). Eutrophication in the region is characterized by harmful algal blooms and driven by high nutrient concentrations, particularly of P. Soils and aquatic systems in the region are naturally fertile with relatively high concentrations of P (Barica and Allan, 1988); however, since the 1970s, eutrophication issues have continued to increase.…”

4R Management of Phosphorus Fertilizer in the Northern Great Plains

“…Soil and water conservation practices should be selected to match local conditions, to ensure that they apply the “right strategy” in the “right place” (Dodd and Sharpley, 2016). The snowmelt‐dominated runoff and relatively level landscapes of the northern Great Plains create unique challenges for selecting and using conservation strategies that are effective for reducing the risk of P loss in this region (Baulch et al, 2019; Kieta et al, 2018; Tiessen et al, 2010). Those challenges also imply that conservation practices do not easily compensate for suboptimal nutrient management practices, which makes the latter group of practices especially important in this region.…”

The Latitudes, Attitudes, and Platitudes of Watershed Phosphorus Management in North America

“…Indeed, runoff and P mobilization in the Lake Erie and Lake Winnipeg watersheds primarily occur throughout the nongrowing season (Macrae et al, 2007; Ford et al, 2018; King et al, 2018; Plach et al, 2019) and is most often dominated by spring snowmelt (Macrae et al, 2007), although large‐magnitude events can occur at other times of year, including the summer months (Macrae et al, 2010; Van Esbroeck et al, 2017). Mitigation strategies that are effective under rainfall‐dominated conditions during the growing season have not been successful during the winter period (Baulch et al, 2019; Kieta et al, 2018). Around Lake Winnipeg, spring snowmelt over frozen ground represents the dominant P transport pathway, with a shallow frost lens impeding infiltration and therefore rendering ineffective strategies to improve soil infiltration, as described above, or trapping strategies that require infiltration (e.g., riparian buffers zones).…”

“…Climate change is also expected to lead to an intensification of the hydrologic cycle, with greater rainfall volumes and intensities, but also greater periods of drought between rainfall events (Najjar et al, 2010;Verma et al, 2015;Dumanski et al, 2015;Wang et al, 2018). Changes in the timing, form, and intensity of precipitation are already being noted in some regions (Shook and Pomeroy, 2012;Wang et al, 2018;Baulch et al, 2019). Thus, larger contrasts between wet and dry conditions and greater potential for peak flow conditions following intense rainfall are expected.…”

“…Further, cropping, nutrient management, and drainage systems reflect the interaction of this climate with local physiography. Different mitigation strategies are needed to account for these contrasting conditions (Ulen et al, 2012; Baulch et al, 2019). Our ability to recommend and employ P mitigation efforts is further challenged by the fact that we are working toward a “moving target,” where temperatures are increasing and the hydrologic cycle is intensifying (Ockenden et al, 2017).…”