Considering Soil Potassium Pools with Dissimilar Plant Availability

Soil potassium (K) has traditionally been portrayed as residing in four functional pools: solution K, exchangeable K, interlayer (sometimes referred to as “fixed” or “nonexchangeable”) K, and structural K in primary minerals. However, this four-pool model and associated terminology have created confusion in understanding the dynamics of K supply to plants and the fate of K returned to the soil in fertilizers, residues, or waste products. This chapter presents an alternative framework to depict soil K pools. The framework distinguishes between micas and feldspars as K-bearing primary minerals, based on the presence of K in interlayer positions or three-dimensional framework structures, respectively; identifies a pool of K in neoformed secondary minerals that can include fertilizer reaction products; and replaces the “exchangeable” K pool with a pool defined as “surfaceadsorbed” K, identifying where the K is located and the mechanism by which it is M. J. Bell (*) School of Agriculture and Food Science, The University of Queensland, Brisbane, QLD, Australia e-mail: [email protected] M. D. Ransom · A. M. Florence Department of Agronomy, Kansas State University, Manhattan, KS, USA e-mail: [email protected] M. L. Thompson Department of Agronomy, Iowa State University, Ames, IA, USA e-mail: [email protected] P. Hinsinger Eco&Sols, University of Montpellier, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France e-mail: [email protected] P. W. Moody Department of Science, Information Technology and Innovation, Brisbane, QLD, Australia e-mail: [email protected] C. N. Guppy School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia e-mail: [email protected] © The Author(s) 2021 T. S. Murrell et al. (eds.), Improving Potassium Recommendations for Agricultural Crops, https://doi.org/10.1007/978-3-030-59197-7_7 163 held rather than identification based on particular soil testing procedures. In this chapter, we discuss these K pools and their behavior in relation to plant K acquisition and soil K dynamics.