One of the most important parts in a precision farming system is the crop yield mapping. The pre-processing of the point data from combine harvesters, the transfer of the yield data onto the management grid and the interpolation of the yields are discussed, as well as using of the yield data themselves. The goal of the contribution was to verify, with the help of the field measuring on two stations, the dependence of the yield obtained by processing of the measured yield data from the combine harvester (where the yield monitor is installed) on the weighted yield. This is because of yield va­ria­bi­li­ty, which is the basic dependent variable of majority belonging to the rest kinds of field variation that provides the basic information about the field. Afterwards it is possible to transfer the yield data as the base for the variable application of the fertilizer. By this we access yield effects for the different site – specific treatment.