Enhanced N2O Production Induced by Soil Salinity at a Specific Range

Yawei Li,Zhiming Qi,Qi Wei,Boyi Liu,Shimeng Liu,Linxian Liao,Haiyu Wang,Junzeng Xu

doi:10.3390/ijerph17145169

Abstract

Nitrous oxide (N2O) as a by-product of soil nitrogen (N) cylces, its production may be affected by soil salinity which have been proved to have significant negative effect on soil N transformation processes. The response of N2O production across a range of different soil salinities is poorly documented; accordingly, we conducted a laboratory incubation experiment using an array of soils bearing six different salinity levels ranging from 0.25 to 6.17 dS m−1. With ammonium-rich organic fertilizer as their N source, the soils were incubated at three soil moisture () levels—50%, 75% and 100% of field capacity ()—for six weeks. Both N2O fluxes and concentrations of ammonium, nitrite and nitrate (NH4+-N, NO2−-N and NO3−-N) were measured throughout the incubation period. The rates of NH4+-N consumption and NO3−-N accumulation increased with increasing soil moisture and decreased with increasing soil salinity, while the accumulation of NO2−-N increased first then decreased with increasing soil salinity. N2O emissions were significantly promoted by greater soil moisture. As soil salinity increased from 0.25 to 6.17 dS m−1, N2O emissions from soil first increased then decreased at all three soil moisture levels, with N2O emissions peaking at electric conductivity (EC) values of 1.01 and 2.02 dS m−1. N2O emissions form saline soil were found significantly positively correlated to soil NO2−-N accumulation. The present results suggest that greater soil salinity inhibits both steps of nitrification, but that its inhibition of nitrite oxidation is stronger than that on ammonia oxidation, which leads to higher NO2−-N accumulation and enhanced N2O emissions in soil with a specific salinity range.

Highlights

With more than 8.3 × 106 km2 of salt-affected lands globally, soil salinization is one of the most severe forms of land degradation [1]
The cumulative nitrous oxide (N2 O) emissions at 100% of θfc for all salinity treatments were 5.0–15.3 times greater than cumulative N2O emissions at 100% of θfc for all salinity treatments were 5.0–15.3 times greater than those at 75% θfc, and 4.7−37.6 times greater than those at 50% θfc (Figure 4)
Nitrous oxide emissions were found significantly increased with an increasing soil salinity within a certain range of 1.01–2.02 dS m−1, it increased in different magnitudes under three soil moisture levels

Summary

Introduction

With more than 8.3 × 106 km of salt-affected lands globally, soil salinization is one of the most severe forms of land degradation [1]. Situated in arid and semi-arid regions [2], the expanse of such lands is increasing in several regions of the world due to climate change, seawater intrusion and irresponsible irrigation and drainage management [3]. Soil salinization severely inhibits plant growth and production [4], and has a profound impact on soil nutrient cycling: soil nitrogen (N). Transformations are significantly altered in salt-affected soils [5,6]. Emissions of nitrous oxide (N2 O), a by-product of soil N transformation and a potent greenhouse gas, from different ecosystems has been a hot research topic in the past decades [7,8]. Public Health 2020, 17, 5169; doi:10.3390/ijerph17145169 www.mdpi.com/journal/ijerph

Methods

Discussion

Conclusion