Effect of sodium chloride on denitrification in glucose amended soil treated with ammonium and nitrate nitrogen

Laboratory incubations were conducted to study the effect of sodium chloride (NaCl) on denitrification and respiratory gases (CO 2 , O 2 ) from soil treated with ammonium or nitrate and incubated at 20 % moisture. The same samples were assayed for denitrifying enzyme activity (DEA) after incubation at 40 % moisture with glucose and NO 3 – . Under aerobic conditions (20 % water content), a flush of activity was observed at 6 hours after start of incubation and subsided to negligible levels at 12 hours. Sodium chloride significantly depressed N 2 O and CO 2 emissions and O 2 consumption. Significantly more loss of N 2 O occurred from NH 4 + ‐ than NO 3 – ‐treated soil at all NaCl levels and was attributed to higher microbial activity. A highly significant positive correlation was obtained between N 2 O emission and respiratory gases. The respiratory quotient (CO 2 evolved/O 2 ) was higher for NH 4 + ‐treated soil and decreased with the amount of NaCl. At 40 % moisture, N 2 O emissions were higher than at 20 % and peaked at 37 hours followed by a sharp decrease. Short‐term incubations of soil with NH 4 + or NO 3 – did not have an effect on denitrifying enzyme activity (DEA) while NaCl had a positive effect, particularly in previously NO 3 – ‐treated soil.