Potassium quantity - intensity (Q/I) curves for two soils as affected by Zeolite additions

Potassium is one of the most plentiful nutrients in the soil surface with important physiological roles in plant، improving their quality. Quantity-intensity (Q/I) relationships present beneficial information when assessing plant potassium availability and fertilizer application management. The objective of this research was to determine the K Q/I relationships and their related parameters; labile K (∆Ko)، slowly exchangeable K (KX)، potassium activity ratio (ARK)، potassium activity ratio at equilibrium (ARke) and potassium buffering capacity (PBCk) for two different soils as are affected by zeolite additions. Soil samples with illite and kaolinite prevailing in their clay fraction obtained respectively from 0-30 cm depths of Rahmat Abad series (Gorgan University-Pardis) and Lavark (Isfahan). Texture، cation exchang capacity (CEC) and K (using 1 M NH4OAc) were same for both soils. Zeolite increased PBCk with high K intensities in soil solution. With ARke less than (mol-1) 0. 5/ (meq. 100g-1) 0. 001 in a soil with illite prevailing in clay fraction، K from non specific sites in zeolite may increase buffering rate for plant roots K uptake. For plant potassium uptake in Pardis (no correlation with NH4-OAc extractable potassium)، no correlation is expected with potassium buffering capacity (PBCk) but there might be a correlation with potassium activity ratio at equilibrium (ARke) or labile K (∆Ko) which needs further investigation.