Development of Soil Nitrification Inhibitors: Activity of 6, 6-disubstituted-l, 4, 5, 6-tetrahydro-l, 2, 4, 5-tetrazine-3 (2H) thions

6, 6-Disubstituted-l, 4, 5, 6-tetrahydro-l, 2, 4, 5-tetrazine-3(2H)thiones, synthesized by condensing aldehydes/ketones with thiocarbohydrazide, and combining N containing hyterocyclics with the C=S moiety, have been found as only mild nitrification inhibitors. 6-Methyl-l, 4, 5, 6-tetrahydro-l, 2, 4, 5-tetrazine-3 (3H) thione was the mosl effective, showing 56% nitrification inhibition up to 16 d at 10% of the applied nitrogen.