Complex zinc (II) compounds as nitrification inhibitors

Abstract

This work was aimed at synthesizing a number of new complex compounds, nitrification inhibitors containing Zn2+, and determining their structure, composition and biological activity. Four substances with different ratios of ligands (4-amino-1,2,4-trazole (ATC)) and dicyandiamide (DCD)) were synthesized. Some physicochemical properties were determined, such as thermal behavior and solubility of complexes in pure KAS-28 (a saturated solution of urea and ammonium nitrate containing 28% nitrogen) and its 50 % solution. The content of Zn2+ in each substance was determined. The functional groups belonging to the ligands were established using IR spectroscopy. It was established that the attachment of ATC in solution takes place monodentately to one zinc atom through the N1 atom, and in crystals it occurs bidentately to two zinc atoms through the N1 and N2 atoms (1, 2-coordination). The attachment of DCD, most likely, proceeds through the C=NH group. The level of biological activity of complex compounds was determined by the potentiometric method. A direct measurement of the concentration of NH4+ and NO3– ions was carried out. The greatest influence on the nitrification process was found in the complex with the following probable empirical formula [Zn(ATC)2(DCD)1(H2O)1]SO4. When using it, the smallest loss of ammonium and the smallest formation of nitrates in the soil were observed. This indicates the influence on both stages of nitrification.