Organic phosphorus, as a form of phosphorus in the soil, is a constituent of numerous chemical compounds, of which depends availability of phosphorus to plants. Most agricultural soils contain 20 to 60 % of organically bound phosphorus, and it comes into the soil after disintegration of plant residues or addition of organic fertilizer and is subject to the mineralization process under the influence of microorganisms in the soil. Microbiological transformations of phosphorus include processes of mineralization of organic phosphorous compounds (phosphomineralization), degradation of phosphorous inorganic compounds (phosphomobilization) and reduction of oxidized inorganic phosphorus forms (dephosphorylation). The aim of this study was to examine the influence of microbial fertilizer on increasing the availability of organic phosphorus in the soil. It is also assumed that the content of organic phosphorus in the soil, as well as the activity of microorganisms, are under a great influence of humus content and soil pH, so the aim was to determine the correlations between these properties. Statistical analysis of data (ANOVA) showed a statistically significant difference in the content of organic phosphorus, before trial setting without chloroform on KMP and pMP treatments while statistically significant difference in the content of organic phosphorus with chloroform was determined between the K and p treatments. A very high statistically significant correlation, also, was found between the content of organic phosphorus and humus content before trial setting (r = 0,94), which significantly decreased (r = 0,42) after the soybean harvest. High correlation was also found between exchangeable acidity and organic phosphorus content before trial setting (r = 0,67), which also decreased after soybean harvest (r = 0,53). However, after the soybean harvest, the data analysis did not show statistically significant differences in organic phosphorus content between the treatments with nor without the use of chloroform. Generally, it can be concluded that the application of microbial fertilizer have led to an increase in the availability of organic phosphorus in the soil.