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Purpose: The effects of soil pH manipulation and KCl addition on NO production in adjacent forest and grassland soils in central Alberta were studied in a 16-day laboratory incubation experiment. Materials and methods: The soils were subjected to four pH and two salt treatments: CK (control)-no addition of acid or alkali solution (pH 4.50 and 4.48 for the forest and grassland soils, respectively; same below); HCl-addition of HCl solution to lower soil pH (3.95 and 3.75); L-KOH and H-KOH-addition of 6 mL of 0.2 (5.36 and 5.57) and 0.4 (6.41 and 6.72) mol L KOH solution, respectively, to increase soil pH to two different levels. In order to differentiate between the effect of a change in pH and of changed salt concentrations on NO production, 6 mL of 0.2 (L-KCl) (4.56 and 4.41) or 0.4 mol L (H-KCl) (4.59 and 4.42) KCl solutions were also applied as treatments to create two levels of salt application rates. Results and discussion: Increasing pH promoted gross nitrification and cumulative NO production in both soils, particularly in the forest soil. However, cumulative NO production decreased in the forest soil but increased in the grassland soil when pH decreased. Cumulative NO production in the grassland soil was 36 times higher in the L-KCl treatment (1,442 μg N kg) than in the CK (40 μg N kg), whereas the H-KCl treatment reduced cumulative NO production. In contrast, in the forest soil, both KCl treatments reduced cumulative NO production. Conclusions: (1) The most important factor to increase NO production in this study was increasing soil pH, suggesting that careful soil pH management could be used as a tool to control soil NO production; (2) salt effect was also involved in affecting NO production. [ABSTRACT FROM AUTHOR]