In a long-term maize fertilization experiment set up on calcareous, sandy soil in the mid-region of rivers Danube and Tisza, the individual variability of the hybrid NK-PX MSC 20 (hybrid of Martonvasar) was studied in the respect of ear mass quantity Twenty ears were taken and individually measured from each plot in the five series, six treatments (phi K-240, N120P60K240, N120P120K240, N240P60K240, N240P120K240). Based on the tests and evaluations, the results can be summarized as follows: The differences between the repetition (soil heterogenity) appeared also in the individual ear masses. On the average of the fertilization treatments the individual ear yield varied in the repetitions between 184 grams and 260 grams. Due to the soil heterogenity between the repetitions, there were significant differences both in fertilization treatments and in the average of those. The standard deviations characterizing the individual variability, showed inhomogenity, significant differences between the repetitions and soils, respectively. The fertilization raised significantly the individual ear yield mass from 120 g to 260 grams. The standard deviations, the individual variability of ear masses showed provable deviations on the effect of fertilization. Its extent proved to be the smallest at control and at good supply level. The ratio of maximum and minimum ear masses was at the individual measurements within the extreme values of 1:2,5 and 1:6,7. The individual variability of a plant (in present case the maize ear mass) is a genetical basis that may be influenced in cartain limits by external factors (e.g soil) and human activity (e.g. fertilization). Its extent in the experiment can be altered by increasing the replications and individual number of samplings.