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.
Highlights
The Northern Great Plains is an area of fertile soils and high agricultural productivity, considered part of the ‘bread basket’ of North America (Fig. 1)
We review the state of our knowledge among multiple management practices applied
While nutrient release from soil organic matter (SOM) likely occurs with every tillage pass, the effects are most evident in nitrate concentrations in snowmelt runoff from soils that had been tilled the previous fall either after crop harvest or during fallow
Summary
The Northern Great Plains is an area of fertile soils and high agricultural productivity, considered part of the ‘bread basket’ of North America (Fig. 1). Throughout the region, lakes and rivers are affected by high nutrient concentrations, contributing to harmful cyanobacterial blooms, and loss of ecosystem services (Beaver et al.2014; Kehoe et al 2015; Maheaux et al 2015) This is not a new issue, with evidence of poor water quality, even prior to agricultural development (Palliser and Spry 1968; Hall et al 1999), due to naturally high nutrient concentrations in soils of this landscape (Barica 1987). High spatial and temporal variation affect application of paired designs and before-after study designs for BMP assessment These challenges are acute in regions such as the Northern Great Plains, which are characterized by periodic runoff and high inter-annual variability. We briefly https://mc06.manuscriptcentral.com/er-pubs summarize key aspects of nutrient management in this region and focus mainly on the effect of soil and water management BMPs on nutrient transport in the Northern Great Plains. Their transport, both spatially and temporally, is beyond the scope of this review
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