Phosphorus transport along the cropland–riparian–stream continuum in cold climate agroecosystems: A review

Authors: Young, Eric; ROSS, DONALD - University Of Vermont; JASI, DEB - University Of Delaware; VIDON, PHILIPPE - State University Of New York- College Of Environmental Science And Forestry

Submitted to: Soil Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2021
Publication Date: 3/9/2021
Citation: Young, E.O., Ross, D.S., Jasi, D.P., Vidon, P.G. 2021. Phosphorus transport along the cropland–riparian–stream continuum in cold climate agroecosystems: A review. Soil Systems. https://doi.org/10.3390/soilsystems5010015.
DOI: https://doi.org/10.3390/soilsystems5010015

Interpretive Summary: Adequate phosphorus (P) availability in agricultural soils is important to support profitable agricultural production in the US and worldwide. However, P lost form agricultural fields in runoff and erosion can contribute to nuisance algae blooms in freshwater systems and contribute to water quality degradation. In dairy systems, soil nutrient management practices (soil P testing, manure management, riparian buffers) are important for ensuring sufficient P while also reducing the risk of runoff P loss from individual crop fields. Many states use agronomic P site indices to categorically or quantitatively assess P transport risk, which combine P source (soil test P, manure/fertilizer P) and transport factors (predicted erosion, soil type/drainage, distance to nearest stream) and assign an individual score reflecting a given field’s P loss potential. Wisconsin is one of the few states accounting for seasonal effects on P transport potential and also provide runoff P loss estimates. While current P transport models and site indices are useful, there is a general consensus that current tools and practices for mitigating P loss from cropland are inadequate in many cold climate regions for maintaining desired water quality. New approaches are needed to improve overall understanding of P transport in cold climate dairy agroecosystems and develop more quantitative P loss estimates.

Technical Abstract: Phosphorus (P) loss from cropland is a global concern. Cold climates (CCs) have several P transport challenges, including freeze-thaw cycles and wet soils with high runoff potential. Riparian buffer zones (uncultivated areas between cropland and streams; RBZs) can overwhelmingly affect P transport to streams, however few RBZ studies focus on P and include measures in both cropland and RBZs. Watershed P transport models and indices help identify critical source areas, however RBZ effects on P transport and cropland-RBZ-stream connectivity are generally not accounted for and the coarse resolution of model outputs can limit applicability. Variable source area hydrology and site microtopography are critical landscape drivers of P transport and need more consideration. Light detection and ranging (LiDAR) and other imagery acquisition tools show promise for mapping cropland-RBZ hydrology, however a better mechanistic understanding of processes controlling mobile P species in relation to hydrology, legacy P, and agricultural management is needed. Broader predictive approaches for multiple, highly resolved data (Bayesian neural networks, artificial intelligence, machine learning algorithms and hybrid models) should be considered to improve P loss prediction and to develop real-time P transport risk tools that quantify risk and uncertainty.