Differential potassium buffer behavior of individual soils related to potassium corrective treatments

Although the basic chemistry and behavior of potassium in the soil is well understood, little of this knowledge is used in soil testing and practical soil fertility mangement. In this study the K buffer behavior of three individual soils (Hagerstown silt loam (Typic Hapludalf), Gatesburg sand (Entic Haplorthod) and Gilpin channery silt loam (Typic Hapludult)) was investigated. The buffer relationships determined indicated very different K behavior for these soils even though exchangeable K soil tests indicated similar K levels. It was also determined that for these soils the buffer relationship was apparently independent of previous K management, indicating that the K buffer behavior could be included as part of soil characterization data. The role of nonexchangeable K in determining K buffer behavior was also investigated. It was found that the levels of solution K where the release of nonexchangeable K becomes measurable (0.27 − 0.83 × 10⁻⁴ M) are similar to solution K levels reportedly required for crop growth (0.02 − 0.95 × 10⁻⁴ M). It was also found that these soils were capable of maintaining a relatively high level of exchangeable K even after extraction of significant amounts of nonexchangeable K with sodium tetraphenyl boron. It was concluded that K buffering behavior of individual soils could and should be included in K management decisions involving corrective soil treatments and/or crop removal estimation. Otherwise, based on current soil tests, soils with very different K buffer behavior will be treated similarly.