A long-term static fertilization experiment was carried out at the Mochełek Experimental Station. Soil samples were taken from the 5–25 cm layer of the Ap horizon in the 52nd year of the experiment at the moment of cultivation of spring barley with red clover as companion crop at the following dates: 28 April, 25 May, 29 June, and 07 September. The content of total sulphur (0.041–0.202 g kg-1) in the soil under study should be considered low. Soils samples taken from plots fertilized with manure and minerals contained more of this element. The values of the C:S ratio changed with soil fertilization. It reached 25 in case of the control, while it increased to 44 and 49 for the plots fertilized exclusively with minerals and fertilized both with manure and mineral fertilizers, respectively. Such a C:S value indicated high resistance of sulphur to mineralization. This observation was additionaly confirmed by the content of mineral sulphur amounting to 8–16% of the total S, supporting an opinion that sulphur in the soil under study is not available to plants at a great deal. A significant increase of the S-SO42- content (13.98–17.45 mg kg-1) was observed in soil samples fertilized with manure and mineral fertilizers. Concentration of available sulphur assayed by the KCl-40 test reached 34–48% of total sulphur. The content of this sulphur fraction changed over vegetation period. The lowest value was noted in the samples taken in September.
Arylosulphatase activity ranged from 16.98 to 30.83 g PNP g-1 h-1. It reached its peak in the case of soil sampled at the beginning of spring barley vegetation period. The enzyme was more active in the soil fertilized with minerals and manure than in other samples.