Q/I Parameters of Potassium in the Soils of Mazandaran under Tobacco Cultivation

Quantity-intensity (Q/I) relationships provide insight into a soil’s immediate K status. Q/I parameters of potassium and their relationships with some soil properties were investigated on 15 combined top soil samples (0-30 Cm) collected from the cultivated tobacco fields in Mazandaran. The amount of the equilibrium activity ratio for potassium (ARe^K) ranged from 0.0009 to 0.0313 (Cmol/l)^0.5. The adsorbed K held specifically at edge /wedge shaped positions in Darabkola, Chalamardi and Ervet soils. In contrast, soils of Valaghoz and Parvarichabad held the K at planar surfaces. Labile K (-DK°) ranged from 0.007 to 1.44 with a mean value of 0.332 Cmol/kg. The lowest value found in Ervet soil and the highest one in Parvarichabad soil. However, NH4AOc-exchangeable K values were always considerably higher than DK° values. This suggests that there were over estimation by NH4AOc (1N). Therefore, DK° is a better estimate of soil labile K than exchangeable K by NH4AOc (1N) soil test. The Kx values ranged from 0.050 to 1.026 Cmol/kg and the values for PBC^K varied from 11.29 to 208.60 with an average of 99.24 (Cmol/kg)/(Cmol/l)^0.5. The Paja and Darabkola-baboyeh soils had the lowest and highest values for PBC^K, respectively. There were significantly and positively correlations with each other among the DK°, ARe^K and NH4AOc-K at 1% probability level. The Q/I parameters provide useful information for understanding available K stauts of soils and can be used for K-fertilizer recommendations.