Phosphorus (P) is an important driver of terrestrial and aquatic ecosystem productivity in cold climate regions. Agriculture is an important contributor of P loss to surface and groundwater and is a leading cause of impaired water quality in US cold climate regions. Implementing agricultural management practices that can mitigate P transport to open waters and streams while maintaining farm viability is critical. Nutrient loss in cold climate agroecosystems is challenged by extended periods of high overland flow potential, frozen soils, and large snowmelt runoff events. In addition to in-field practices, riparian areas (land between crop field edges and streams) should be evaluated and managed appropriately to reduce P transport potential, particularly in sensitive watersheds where cropland overland and subsurface flows contribute to streamflow. Riparian characteristics including slope, vegetation, and connectivity to adjoining cropland all have important impacts on P transport potential to streams. In particular, the hydrologic gradient between cropland and streams and associated changes in soil properties are often linked with changes in the quantity and molecular speciation of P in aqueous and solid phases. Organic carbon, pH, redox potential, and mineralogy impose important constraints on P sorption/desorption and bioavailability in both agricultural and riparian soils. Soil hydrology is an overarching factor affecting runoff flow pathways and P desorption potential from extended water saturation including the reductive dissolution of iron and manganese-P species. A better understanding of linkages between molecular- and field-scale soil processes driving P speciation and fluxes in differing cold climate environments will aid P transport decision support tools aimed at curbing P transport risk to streams.

Phosphorus Transport along the Agricultural-Riparian-Stream Continuum in Cold Climates: Managing for Improved Water Quality

ACS Fall 2021

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