The links between potassium availability and soil exchangeable calcium, magnesium, and aluminum are mediated by lime in acidic soil.

Purpose: The aims of this study were to investigate the links between potassium (K) uptake by crops and soil K, exchangeable calcium (Ca²⁺), magnesium (Mg²⁺), and aluminum (Al³⁺) when using lime in acidic soil in southern China.Materials and methods: Soil samples of three treatments (chemical NP fertilizers, NPK, and NPK plus straw (NPKS)) were collected from a 26-year field experiment (0-20 cm) and then a rhizobox experiment was conducted with seven lime application rates (0-2.26 g kg⁻¹). We investigated the soil exchangeable K⁺, Ca²⁺, Mg²⁺, and Al³⁺ and non-exchangeable K (NEK) in the rhizosphere soil (RS) and non-rhizosphere soils (NRS), and K uptake by crops.Results and discussion: As lime addition rates increased, the average concentration of exchangeable K (EK) in RS under NPK and NPKS treatments decreased to 46.5 mg kg⁻¹ and 70.4 mg kg⁻¹ for maize and wheat, respectively. In treatments with lime application, the NEK concentration was higher in RS and NRS compared with the no-lime in NP treatment but was lower in RS in treatments with K fertilizer input (NPK and NPKS). The K uptake by crops under lime application significantly (p < 0.05) increased by 37.6% to 155.1% compared with the no-lime treatments. Lime application significantly increased soil exchangeable Ca²⁺ (42.9 to 255.7%) and decreased exchangeable Al³⁺ (23.7 to 86.6%). According to structural equation modeling, lime indirectly influenced K uptake by crops through its effects on soil exchangeable Ca²⁺+Mg²⁺ and Al³⁺, EK, and NEK, which accounted for up to 39% (RS) and 46% (NRS) of the variation in the K uptake by crops. Lime directly and negatively affected EK and NEK in NRS but had no direct effects on EK and NEK in RS.Conclusions: Our results suggested that lime-induced K uptake by crops was mediated by K⁺, Ca²⁺, and Al³⁺, and that lime application resulted in higher soil K availability. [ABSTRACT FROM AUTHOR]