In this work magnetic susceptibility of soil samples originating from two different cultivation systems: mineral fertilization (conventional) and organic farming has been investigated. The investigations were carried out for soils collected from the long-term static experiment. The soil samples were taken from humus horizon under barley and winter wheat during 3 years (1996-1998). The sampling was made three times each year: in spring, after sprouting; in summer, during intensive growth and in autumn, post harvest. Soil reaction, organic carbon and granulometric composition were also determined. All measurements were repeated three times at the temperature 20°C. The magnetic susceptibility was only slightly dependent on the cultivation system. For the soils from organic farming system, the average value of magnetic susceptibility was equal to χ = 9.72 x 10^–6 SI, whereas the average magnetic susceptibility for the soils from conventional cultivation was slightly lower and equal to χ = 8.03 x 10^–6 SI. The duration time of the field experiment and the sampling period did practically not influence the values of the magnetic susceptibility. Those values were dependent on the kind of cultivated cereals. The magnetic susceptibility was higher for the samples taken under barley than for the samples taken under wheat Also, greater differentiation of the magnetic susceptibility was observed from the samples from organic farming than for the samples from conventional cultivation. Both soil reaction and the content of organic carbon did not correlate with the magnetic susceptibility. This can be explained by a rather short duration period of our experiments and fine changes of soil reaction during only three years. However, the experiments confirmed the existence of the correlations between the magnetic susceptibility and the granulomctric composition of the investigated soils.