Nitric Oxide and Nitrous Oxide Production from Soil: Water and Oxygen Effects

Abstract

Abstract This study was designed to determine the effects of water and O 2 on the speciation of denitrification gases (NO and N 2 O). Nitric oxide was found to be the principal end product from soil incubated under low‐moisture conditions, whereas the relative amount of N 2 O increased under wetter moisture regimes. The total amount of NO plus N 2 O produced increased with increasing water content for the Brookston clay loam (fine‐loamy, mixed, mesic Typic Argiaguoll), whereas it peaked at 150 g kg −1 (15%) water content with the Fox sandy loam (fine‐loamy over sandy or sandy or sandy‐skeletal, mixed, mesic, Typic Hapludalf). The decrease in NO plus N 2 O at higher water contents was probably the result of the subsequent reduction of N 2 O to N 2 in the Fox sandy loam soil. The residence time of the denitrification gases in the soil increased with increasing water content, hence facilitating the subsequent conversions of NO to N 2 O and N 2 . The thickness of the water film surrounding the microbes affected both the diffusion of O 2 through the water and into the microbes as well as the diffusion of denitrification gases (NO, N 2 O, and N 2 ) from the microbes into the atmosphere. In the sandy loam soil, O 2 content and soil water affected both the amount and species of evolved denitrification gases. Oxygen was more effective in decreasing NO production at lower than at higher water contents.