The atmospheric nitrogen fixation thermodynamic probability study depending on the mixed mineral fertilizers composition

The mixed mineral fertilizers component composition effect on the binding atmospheric nitrogen thermodynamic probability in soils was studied. The studies were carried out by the physical and chemical modelling method based on the Selector software package. The systems following final indicators were calculated: the Gibbs system energy, the corresponding independent components chemical potentials, the solution components amount, the evolved gases amount, the solution pH, and the system redox potential. The results obtained in this work make it possible to conclude that the atmospheric nitrogen fixation in a nitrate ion form is thermodynamically resolved, and the problem lies in finding conditions conducive to this process implementation. It was revealed that the thermodynamic probability of atmospheric nitrogen oxidation depends both on the mineral fertilizer main component and on this component form, in particular, on its redox or acid-base characteristics. According to the modelling results, limestone as a mixed mineral fertilizers component contributes to a significant increase in the binding atmospheric nitrogen thermodynamic probability with the most oxidized form formation. The nitrogen presence in mixed mineral fertilizers in the most oxidized form (the nitrogen oxidation state is +5) can contribute to the conditions' creation favorable for fixing atmospheric nitrogen. An increase in the urea and ammonium hydrate content in ammonia water, where nitrogen is in the maximum reduced oxidation state of -3, on the contrary, leads to a decrease in the atmospheric nitrogen binding thermodynamic probability to form oxide forms.