Dolomite and limestone influence on oxygen and nitrogen activity in mixed mineral fertilizers

The purpose of the study is a comparative analysis of the effect of dolomite and limestone, widely used components of mixed mineral fertilizers, on the activity of the most important biogenic elements, in particular, oxygen and nitrogen. The influence of dolomite and limestone used in the composition of mixed mineral fertilizers on the activity of the most important biogenic elements, in particular oxygen and nitrogen, was studied by the method of physicochemical modeling using the Selector software package. In binary mixed mineral fertilizers based on dolomite or limestone with the participation of double superphosphate and potassium chloride, the chemical activity of oxygen increases with an increase in the content of dolomite or limestone in mixtures in the solubility range of these minerals. In binary mixed mineral fertilizers with the participation of ammonium nitrate, the chemical activity of oxygen increases with an increase in the content of dolomite and only to a small extent with an increase in the content of limestone. The chemical activity of nitrogen decreases for all variants of mixtures with an increase in the content of dolomite and limestone in mixtures. At the same time, in the limestone-ammonium nitrate system, the decrease in nitrogen activity is minimal. In the systems limestone - ammonium nitrate and dolomite - ammonium nitrate, an increased content of nitrate ions is noted, and a higher content is in a mixture based on limestone. The formation of additional nitrate ions in the systems under study may be due to the thermodynamic probability of atmospheric nitrogen fixation, which is consistent with the change in the redox potentials of the systems. It can be assumed that calcium ions have a positive effect on the process of atmospheric nitrogen fixation, which is more pronounced in limestone, where the mass fraction of calcium is higher. The influence of dolomite and limestone on the properties of the studied mixed mineral fertilizers includes two components: an increase in the activity of oxygen in mixtures; creating a thermodynamic probability of fixing atmospheric nitrogen, more pronounced for mixed fertilizers based on limestone.