Effects of ammonium nitrate, wheat straw and Phylazonit MC bacterial fertilizer on the N supply of soil

An incubation experiment was set up to investigate the effects of NPK fertilizers, wheat straw and food waste compost in combination with Phylazonit MC biofertilizer on the changes in 0.01 M CaCl2 extractable nitrogen forms (NO3+ -N, NH4+-N, organic-N fraction) of three types of soils. The quantities and changes in CaCl2-NH4+-N mainly depended on the adsorption capacity of soils. Higher CaCl2 extractable NH4+-N values were measured in the calcareous chernozem and sandy soil with the application of NPK treatment, while in case of the chernozem soil with loamy texture no significant differences were found between the NPK and control treatments. NH4+ immobilization appeared in pots given straw treatment. The quantity of CaCl2 -NH4+-N changed within the incubation period, the direction and extent of the change were dependent of the production rates and consumption processes. In all soils the 0.01 M CaCl2 extractable NO3--N was the largest pool for plant nutrition. The highest CaCl2 -NO3--N values were found in pots given NPK and combined NPK+straw treatments, while the lowest values were measured in straw-treated pots. Wheat straw, with higher C/N ratio caused a temporary immobilization, followed by remineralization. Food waste compost, with lower C/N ratio, proved to have a good N supplying capacity. The contrasted effect of straw and compost was more conspicuous in sandy soil, in which the original NO3--N content was the lowest. Higher CaCl2 -organic N values were measured for pots treated with straw and with compost, as compared to the control. During the incubation period the amount of soluble organic-N changed, the direction and extent of the change depended on the soil type and treatments. The effect of Phylazonit MC was on the quantity of CaCl2 extractable N fractions was not really expressed, and the significancy of the effect varied and was dependent of the soil type. Biofertilizer amendment increased the extractable NO3--N in sandy soil, decreased the negative effect of wheat straw, and it also might help in decomposing wheat straw and food waste compost. The application of Phylazonit MC in the calcareous chernozem caused a significantly higher amount of organic-N, especially in straw-treated pots