The paper demonstrates distribution of the content of total and available phosphorus and activity of the alkaline and acid phosphatase against the selected properties of salt-affected Mollic Gleysols. In the adequately prepared soil, the following were determined: pH, total organic carbon, the exchangeable cations (Ca, Mg, Na, K), salinity, the content of phosphorus, the activity of phosphomonoesterases. The distribution of the elements in the soil profiles was described with the value of the Distribution Index. To evaluate the availability of phosphorus, the Index of Mobility was used. The content of phosphorus varies, and it depends on physicochemical soil properties. Both the content of phosphorus available to plants and the activity of phosphatases in the profiles showed a high variation that depends both on the sampling date and on the depth. The lowest content of phosphorus was found in the profiles sampled in spring, during an intensive plant growth, while the greatest content was received in soil profiles sampled in summer. The research showed also a high variation in the time of the activity of phosphatases as well as their changes depending on the soil parameters, which was confirmed by the recorded values of the correlations between the activity of alkaline and acid phosphomonoesterases and the content of carbon, respectively, (r = 0.47, P \ 0.05) and (r = 0.62, P \ 0.05) as well as available phosphorus (r = 0.32, P \ 0.05) and (r = 0.38, P \ 0.05). A many-year seasonal salinity of soil did not decrease the activity of the phosphomonoesterases since it was mostly connected with the natural content of organic carbon.

The research results have shown that the enzyme pH index (0.49-0.83) confirmed the neutral or alkaline nature of the soils. Neither the changes in the content of available phosphorus nor in the activity of dehydrogenases, catalase, alkaline and acid phosphatase in soil were due to the factors triggering soil salinity; they were a result of the naturally high content of carbon of organic compounds, which was statistically verified with the analysis of correlation between the parameters. There were recorded highly significant values of the coefficients of correlation between the content of available phosphorus in soil and the activity of alkaline (r = 0.96; P < 0.05) and acid phosphatase (r = 0.91; P < 0.05) as well as dehydrogenase (r = 0.90; P < 0.05). To sum up, one can state that Mollic Gleysols in Inowrocław are the soils undergoing seasonal salinity; however, a high content of ions responsible for salinity is balanced with a high content of organic carbon, humus, phosphorus and calcium directly affecting the fertility of the soils analyzed. The activity of the enzymes depended on the natural content of carbon of organic compounds and not on the factors affecting the soil salinity, which points to the potential of such tests for soil environment monitoring.