Dissipation of nitrapyrin (nitrification inhibitor) in subtropical soils

Nitrapyrin (2-chloro-6-(trichloromethyl)pyridine) is a specific nitrification inhibitor, applied in soils for reducing the nitrification process of nitrogenous fertilizers. The overall effect of nitrapyrin is enhancing the efficiency of nitrogenous fertilizers in soils and also controlling environmental pollution in water by preventing nitrate leaching in soils. Dissipation of nitrapyrin was evaluated in subtropical soils at two fortification levels of 2 and 4 µg∙g -1 . The extraction of nitrapyrin was done by quick, easy, cheap, rugged and safe (QuEChERS) method and quantitative analysis – by high-performance liquid chromatography (HPLC). Nitrapyrin residues declined consistently with time in both types of soils and were not detectable (<0.05 µg∙g -1 ) on the 45 th day at 2 µg∙g -1 and on the 60 th day at 4 µg∙g -1 application rate. Dissipation of nitrapyrin occurred in a single phase with the persistence data fitting well to the first-order kinetics. The half-life of nitrapyrin was 9.6 and 9.9 d at 2 µg∙g -1 and 16.1 d and 17.3 d at 4 µg∙g -1 application rate in both types of soils. The results revealed higher persistence of nitrapyrin at higher concentration (4 µg∙g -1 ) in both types of soils, probably because of high temperature and humidity in subtropical soils.