potassium status of two clayey calcareous soils treated with zeolite under wetting-drying cycles

Zeolite application to clayey soils may change potassium (k) pools distribution and its release rate. to test this hypothesis, two heavy-textured calcareous soils with different mineralogy (smectitic and mixed by xrd) from southern iran were selected. experiment was a completely randomized factorial arrangement. treatments consisted of two soils and two zeolite levels (0 and 5%) and wetting-drying treatment. soil samples were incubated in 50% of saturation percentage for 90 days. then, three wetting-drying cycles were done on samples. different forms of k and k release to 0.01 m cacl2, hcl and ch3cooh by 12 successive 15 min extractions of soil samples were determined. zeolite increased the content of different k forms in soil 1 (smectitic), while it increased soluble and exchangeable k and decreased non-exchangeable k in soil 2 (mixed mineralogy). this may be due to the high cec (189 cmol(+)/kg) and k content (2.13% k2o) of the used zeolite. wetting-drying cycles increased non-exchangeable k in soil 1 and exchangeable k in zeolite treated soils. cacl2 extracted more k than hcl and ch3cooh solutions (682, 281 and 292 mg kg^-1, respectively) because ca ions are more efficient than h ions in replacing k from surface sites in the k-bearing minerals. zeolite and wetting-drying had no effect on k release from soil 1 while they significantly decreased k release rate from soil 2.