Study of Potassiun Status and Effect of Physical and Chemical Properties of Soil on it in Paddy Soils of Guilan Province

The soil potassium status and effect of soil physical and chemical properties on it were investigated using 109 surface soils (0-30cm) from four regions in Guilan province. Neutral molar ammonium acetate extractable K (K-NH4OAc), boiling molar nitric acid extractable K (K-HNO3) and water soluble K were determined. Results showed that CEC and clay were normally frequency distributed while distribution frequency of other variables such as silt organic carbon and pH were not normal and have significant skew and kurtosis. In addition sand, K-NH4OAc and K-HNO3 has logarithmic normal distribution. Water-soluble potassium was affected by sand, pH, O.C and K-NH4OAc (R2a=0.73**). Ammonium extractable potassium was affected by soluble potassium, non-exchangeable potassium and CEC (R2a=0.72**). Boiling nitric acid was affected by exchangeable potassium and silt (R2a=0.55**). Geographic distribution of K-NH4OAc data shows amount of it in central parts of Guilan, particularly Sepidrood river watershed is more than other regions. Fomanat region soils have the less clay, CEC, K-NH4OAc and K-HNO3. According this study about 68.8 percent of Guilan soils was classified in the range of medium to very low potassium status.