Exchangeable Characteristics of Potassium in Five Important Soils of Taiwan

The application of potassium fertilizer by farmers is often not appropriate and causing environmental pollution. By understanding the adsorptive characteristics of potassium (K) on different soils, we can prevent excessive application of K‐fertilizer that can cause environmental impact. The Gapon exchange coefficient (K_G), for exchange between K and Ca, was considered as an important factor influencing the adsorption of K. This study was conducted to compare the constant K_G of five important farm soils in Taiwan. The K_G and CEC were then used to predict K buffering capacity (PBC). Finally, the relationship between exchangeable K ratio (E_P) and K adsorption ratio (PAR) was examined. The results show that five soils have same trends, indicating that K_G decreases with increase in K saturation. The CEC and K_G of Liuying (Ly) soil are both high, so that their K buffering capacity is high. The K_G and CEC of Chanjing (Cj) and Sanhua (Sh) soil show moderate values. The CEC of Erling (El) soil is high, but its K_G is low, so that its K buffering capacity is moderate. On the other hand, the K_G of Newniaokang (Nnk) soil is high but its CEC is low, so its K buffering capacity is also moderate. The correlations between E_P and PAR of five soil show linear relationship at three treatments of CaCl₂ concentration. This study may provide an important clue to the fertilization management of K‐fertilizer on the different soil properties in Taiwan.