Comparison of Three Potassium Determination Methods in Fertilizers

A comparison of three methods for the determination of potassium in fertilizers was conducted using 26 fertilizer samples, which were chosen to represent the ones used in the country’s agriculture. Based on physical and chemical properties, the samples were divided into three categories. The amounts of potassium oxide in fertilizers were determined by gravimetric sodium tetra phenyl boron method, volumetric sodium tetra phenyl boron method and flame photometric method. Potassium recovery rate in the three methods were determined using analytical grade material. The results showed that the recovery rate in the three methods was satisfactory. There was no significant difference at the 5% level between the mean value of potassium oxide determined by gravimetric (22.24%), volumetric (22.19%) and flame photometric (22.47 percent) methods, but the difference between flame photometric method and volumetric method was significant at 5% level. Despite small differences in potassium content measured by flame photometric method and volumetric method, the difference was significant in 15 fertilizers, which can be attributed to our failure to eliminate interfering factors and to use internal standard in flame photometric method. The results showed that there was no significant difference between the two extractions methods (boiling method and shaking method). Based on the results of this study, the flame photometric method has acceptable accuracy and precision and is applicable in all Soil, Water, and Fertilizer Laboratories in the country, thus, it can be introduced as an appropriate method along with gravimetric and volumetric tetra phenyl boron methods that are known and used at international level.