Recent work in our laboratory showed that 2-ethynylpyridine is a potent inhibitor of nitrification in soil. To further evaluate this compound as a soil nitrification inhibitor, we compared the effects of 2-ethynylpyridine and 16 compounds patented or proposed as fertilizer amendments for inhibition of nitrification in soil. We measured production of NO2 and NO3 in soils incubated under aerobic conditions at 20, 25, or 30 °C after treatment with (NH4)2SO4 or urea. The data obtained showed that 2-ethynylpyridine compared favorably with nitrapyrin [N-Serve; 2-chloro-6-(trichloromethyl)pyridine] and etridiazole [Dwell; 5-ethoxy-3-trichloromethyl-1,2,4-thiadiazole] for inhibition of nitrification in soil and was considerably more effective than the other nitrification inhibitors tested (dicyandiamide [DCD], thiourea [Tu], guanylthiourea [ASU], potassium azide, 4-amino-1,2,4-triazole [ATC], 2-amino-4-chloro-6-methylpyridine [AM], 2-mercaptobenzothiazole [MBT], 2,4-diamino-6-trichloromethyltriazine, sulfathiazole [ST], sodium thiocarbonate [Na2CS3], N-2,5-dichlorophenylsuccinamide [DCS], 4-nitrobenzotrichloride, 4-mesylbenzotrichloride, and ammonium thiosulfate [(NH4)2S2O3]). Other studies showed that 2-ethynylpyridine is more effective for inhibiting nitrification of NH4-N than of urea-N, that it has very little, if any, effect on hydrolysis of urea or denitrification of NO3 in soil, and that its effectiveness as a soil nitrification inhibitor is markedly affected by soil type and temperature. These findings and other work reported indicate that 2-ethynylpyridine deserves consideration as a fertilizer amendment for retarding nitrification of fertilizer N in soil.
Journal Paper no. J-13760 of the Iowa Agric. and Economics Exp. Stn., Ames. Project 2655. This work was supported in part by the Iowa State Water Resources Research Inst. and by C.I.L. Inc., London, ON, Canada.