Biogenic nitric oxide emission from saline sodic soils in a semiarid region, northeastern China: A laboratory study

Abstract

It is well‐known that nitric oxide (NO) is an important component in nitrogen biogeochemical cycling produced through biological process of nitrification and denitrification in soils, but the production and the consumption processes of NO in sodic saline soil are less understood. Through a series of laboratory experiments focusing on NO biogenic emissions from four kinds of saline sodic soils of different land use in western Songnen Plain northestern China, we found that the optimum soil moisture for the maximum NO production and emission were 14.0%, 9.0%, 9.5%, and 18% water‐filled pore space (WFPS) for soil samples from natural pasture, man‐made pasture, paddy field of saline sodic soil mixed sandy soil, and paddy field of pure saline sodic soil, respectively. For a given moisture, NO fluxes increased exponentially with soil temperature at any given soil moisture. The optimum soil moisture for the maximum NO emission for a certain soil type, however, was constant and independent of soil temperature. The NO consumption processes for different land uses were similar in all studied saline sodic soils since the difference of NO consumption rate constant in these soils was small (ranged from 1.07 × 10 −6 to 7.45 × 10 −6 m 3 kg −1 s −1 ). The NO emission potential for paddy field soils was about 1.2–2‐fold higher than pasture soils. On the basis of laboratory results and field monitoring data of soil water content and soil temperature, the average NO fluxes from these saline sodic soils in the region were estimated to be 1.3–4.9 ng m −2 s −1 for an entire plant growth period. NO fluxes for pastures mainly occurred in the dry season and were about threefold higher than that for paddy fields, which was strongly influenced by field management.