Dinitrogen and nitrous oxide produced by denitrification and nitrification in soil with and without barley plants

TLDR: In this article, the effect of barley roots on denitrification was examined, and a pot experiment was designed to compare N2O production and denitification in soils with and without barley plants.

Abstract: To examine the effect of barley roots on denitrification, a pot experiment was designed to compare N2O production and denitrification in soils with and without barley plants. Denitrification, N2O resulting from denitrification and nitrification, and respiration were estimated by incubating pots with soil with and without intact plants in plastic bags at high moisture levels. C2H2-inhibition of nitrous oxide reductase (partial pressure of 10 kPa C2H2) was used to determine total denitrification rates while incubations with ambient air and with C2H2 at partial pressures of 2.5–5 Pa were used to estimate the amounts of N2O released from autotrophic nitrification and from denitrification processes. Other sources of N2O were presumed to be negligible. Potential denitrification, nitrification and root biomass were measured in subsamples collected from four soil depths. A positive correlation was found between denitrification rates and root biomass. N2 was the predominant denitrification product found close to roots; N2O formed by non autotrophic nitrifiers, assumed to be denitrifiers originated in soil not affected by growing roots. Apparently, roots promote denitrification because they consumed oxygen, thereby increasing the anaerobic volume of the soil. The ratio of actual to potential denitrification rates increased over time, especially in the presence of roots.