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 (CO2, 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 NO3-. 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 N2O and CO2 emissions and O-2 consumption. Significantly more loss of N2O occurred from NH4+- than NO3--treated soil at all NaCl levels and was attributed to higher microbial activity. A highly significant positive correlation was obtained between N2O emission and respiratory gases. The respiratory quotient (CO2 evolved/O-2) was higher for NH4+-treated soil and decreased with the amount of NaCl. At 40% moisture, N2O emissions were higher than at 20% and peaked at 37 hours followed by a sharp decrease. Short-term incubations of soil with NH4+ or NO3- did not have an effect on denitrifying enzyme activity (DEA) while NaCl had a positive effect, particularly in previously NO3--treated soil.