Uncertainty in phosphorus fluxes and budgets across the U.S. long-term agroecosystem research network

Authors: WELIKHE, PAULINE - Purdue University; Williams, Mark; King, Kevin; Bos, Janae; AKLAND, MARK - University Of Kentucky; Baffaut, Claire; BECK, GLYNN - University Of Kentucky; Bierer, Andrew; Bosch, David - Dave; BROOKS, ERIN - University Of Idaho; Buda, Anthony; Cavigelli, Michel; FAULKNER, JOSHUA - University Of Vermont; Feyereisen, Gary; Fortuna, Ann Marie; Gamble, Joshua; Hanrahan, Brittany; HUSSAIN, MIR ZAMAN - Michigan State University; Kovar, John; LEE, BRAD - University Of Kentucky; Leytem, April; Liebig, Mark; LINE, DANIEL - North Carolina State University; MACRAE, MERRIN - University Of Waterloo; Moorman, Thomas; Moriasi, Daniel; MUMBI, ROSE - Purdue University; NELSON, NATHAN - Kansas State University; ORTEGA-PIECK, ALINE - University Of Idaho; OSMOND, DEANA - North Carolina State University; Penn, Chad; Pisani, Oliva; Reba, Michele; Smith, Douglas; UNRINE, JASON - University Of Kentucky; WEBB, PEARL - University Of Arkansas; White, Kathryn; WILSON, HENRY - Agriculture And Agri-Food Canada; Witthaus, Lindsey

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2023
Publication Date: 5/5/2023
Citation: Welikhe, P., Williams, M.R., King, K.W., Bos, J.H., Akland, M., Baffaut, C., Beck, G., Bierer, A.M., Bosch, D.D., Brooks, E., Buda, A.R., Cavigelli, M.A., Faulkner, J., Feyereisen, G.W., Fortuna, A., Gamble, J.D., Hanrahan, B.R., Hussain, M., Kovar, J.L., Lee, B., Leytem, A.B., Liebig, M.A., Line, D., Macrae, M., Moorman, T.B., Moriasi, D.N., Mumbi, R., Nelson, N., Ortega-Pieck, A., Osmond, D., Penn, C.J., Pisani, O., Reba, M.L., Smith, D.R., Unrine, J., Webb, P., White, K.E., Wilson, H., Witthaus, L.M. 2023. Uncertainty in phosphorus fluxes and budgets across the U.S. long-term agroecosystem research network. Journal of Environmental Quality. 52(4):837-885. https://doi.org/10.1002/jeq2.20485.
DOI: https://doi.org/10.1002/jeq2.20485

Interpretive Summary: Phosphorus is an essential nutrient for crop growth and is routinely applied to agricultural lands; however, small amounts of phosphorus entering surface waters can cause eutrophication and harmful algal blooms. In this study, we use data collected from 24 research locations across the U.S. and Canada to better understand phosphorus inputs and outputs to diverse agricultural production systems. Phosphorus inputs (fertilizer/manre application, atmospheric deposition, phosphorus applied in irrigation water) and phosphorus outputs (crop removal, losses in runoff and tile drainage) were used to calculate phosphorus budgets for 61 production systems including cropland, forage, rangeland, and bioenergy systems. Inputs, outputs, and budgets were highly variable across the production systems. Results indicate areas where improved data collection could further our understanding of phosphorus cycling and transport. Findings also highlight important steps such as efficient use of fertilizers, adoption of P-based manure management, and consideration crop rotation for improved phosphorus management.

Technical Abstract: Phosphorus (P) budgets can be useful tools for understanding nutrient cycling and quantifying the effectiveness of nutrient management planning and policies; however, uncertainties in agricultural nutrient budgets are not often quantitatively assessed. The objective of this study was to evaluate uncertainty in P fluxes (fertilizer/manure application, atmospheric deposition, irrigation, crop removal, surface runoff, leachate) and the propagation of these uncertainties to annual P budgets. Data from 56 cropping systems in the P-FLUX database, which spans diverse rotations and landscapes across the U.S. and Canada, were evaluated. Results showed that across cropping systems, average annual P budget was 22.4 kg P ha-1 (range = -32.7 to 340.6 kg P ha-1), with an average uncertainty of 13.1 kg P ha-1 (range = 1.0 to 87.1 kg P ha-1). Fertilizer/manure application and crop removal were the largest P fluxes across cropping systems and, as a result, accounted for the largest fraction of uncertainty in annual budgets (61 and 37%, respectively). Remaining fluxes individually accounted for <2% of the budget uncertainty. Uncertainties were large enough that determining whether P was increasing, decreasing, or not changing was inconclusive in 39% of the budgets evaluated. Findings indicate that more careful and/or direct measurements of inputs, outputs, and stocks are needed. Recommendations for minimizing uncertainty in P budgets based on the results of the study were developed. Quantifying, communicating, and constraining uncertainty in budgets among production systems and multiple geographies is critical for engaging stakeholders, developing local and national strategies for P reduction, and informing policy.