Inhibition of Nitrification in Soil by Acetylenic Compounds

Abstract

AbstractRecent work has shown that acetylene (ethyne) is a potent inhibitor of nitrification in soil. To discover if substituted acetylenes inhibit nitrification in soil, we determined the effects of seventeen monosubstituted (HC ≡ CR) acetylenes (propyne, 1‐butyne, 2‐ethynylpyridine, phenylacetylene, 3‐butyn‐2‐one, 1‐phenyl‐2‐propyn‐1‐ol, 1‐pentyne, 4‐phenyl‐1‐butyne, 5‐phenyl‐1‐pentyne, 1‐ethynylcycloh‐examine, 2‐propyn‐1‐ol, 2‐propyn‐1‐amine, 1‐hexyne, 3‐butyn‐1‐ol, 1‐heptyne, 1‐octyne, acetylene monocarboxylic acid) and of seven disubstituted (RC ≡ CR′) acetylenes (2‐butyne, 3‐phenyl‐2‐propyn‐1‐ol, diphenylacetylene, 2‐butyn‐1‐ol, 2‐butyn‐1,4‐diol, acetylene dicarboxylic acid, 2‐butynoic acid) on production of (NO‐3 + NO‐2)‐N in soils treated with (NH4)2SO4. The data obtained showed that most of the substituted acetylenes tested inhibited nitrification in soil and that some were potent inhibitors of nitrification. The results with the four gaseous compounds tested showed that acetylene, propyne, and 1‐butyne inhibited nitrification in soils at partial pressures as low as 0.1 or 1.0 Pa, whereas 2‐butyne had little or no effect on nitrification at partial pressures as high as 10 Pa. The data obtained with the 21 nongaseous compounds tested showed that 2‐ethynylpyridine, phenylacetylene, and 3‐butyn‐2‐one had the greatest inhibitory effect on nitrification and that acetylene monocarboxylic acid, acetylene dicarboxylic acid, and 2‐butynoic acid had the least effect. Studies to measure production of C2H2 in soils treated with the nongaseous compounds showed that the inhibition of nitrification observed with these compounds was not due to C2H2 formed by their decomposition in soil. Experiments reported indicate that 2‐ethynylpyridine and phenylacetylene compare favorably with nitrapyrin (N‐Serve) and etridiazole (Dwell) as soil nitrification inhibitors and have potential practical value for retarding nitrification of fertilizer N in soil.