Effects of organic-mineral fertilization and crop rotation (spring barley, clover with grass as companion crop, potato, winter wheat) depleting the soil from organic matter on alkaline phosphatase [E.C.3.1.3.1] activity as well as on the content of total and available phosphorus were studied. The experiment was carried out on typical brown podozolic soil at the Grabowo Experimental Station of the Pulawy Institute of Tillage, Fertilization and Soil Science. Several variants of manure fertilization (control, 20 t ha-1, 40 t ha-1, 60 t ha-1, 80 t ha-1) and mineral nitrogen fertilization (control, 40 kg N ha-1, 80 kg N ha-1, 120 N kg ha-1) were used. Soil samples were taken in 2002 over the vegetation period of winter wheat three times from interrows and twice from the rhizosphere zone. Phosphatase activity was assayed according to Tabatabai and Bremner, total phosphorus concentration as described by Mehta, while available phosphorus by Egnera-Riehma method. Alkaline phosphatase activity and the content of phosphorus fractions under study were higher in soil samples from plots fertilized with higher doses of manure. Fertilization with ammonium nitrate caused negligible changes in the enzyme activity and phosphorus concentration in the soil. An increased activity of the enzyme was noted in samples of the rhizosphere zone. Both phosphatase activity and the content of specific phosphorus forms were significantly affected by the timing of sampling. A statistical analysis of the differences between the studied factors in the rhizosphere zone gave a significant correlation between Pog and FAL (r = 0.37) and PE-R and FAL (r = 0.37).