There were numerous research carried out to determine the optimal number of management zones for variable rate application of fertilizer. It was shown that the number of zones is usually determined by field size and spatial variability of soil properties or crop conditions. However, in real industry it is necessary to consider characteristics of field equipment that will be used to apply fertilizer, and also the economics of variable rate technology. In this study, we investigated the relationship between within-field variability, number of management zones and feasibility of product application using variable rate maps with the different number of zones ranging from 3 to 12. It was found that in many cases the increase of the number of zones did not improve the accuracy of variable rate application of fertilizer. In most cases, the optimal number of management zones varied from 3 to 7. Based on the natural variability, creation of 10-12 zones was not economically efficient and caused major difficulties for the application of fertilizer in the field.