Soil Electrical Conductivity and Water Content Affect Nitrous Oxide and Carbon Dioxide Emissions in Intensively Managed Soils

Abstract

Accumulation of soluble salts resulting from fertilizer N may affect microbial production of N(2)O and CO(2) in soils. This study was conducted to determine the effects of electrical conductivity (EC) and water content on N(2)O and CO(2) production in five soils under intensive cropping. Surface soils from maize fields were washed, repacked and brought to 60% or 90% water-filled pore space (WFPS). Salt mixtures were added to achieve an initial in situ soil EC of 0.5, 1.0, 1.5 and 2.0 dS m(-1). The soil cores were incubated at 25 degrees C for 10 d. Average CO(2) production decreased with increasing EC at both soil water contents, indicating a general reduction in microbial respiration with increasing EC. Average cumulative N(2)O production at 60% WFPS decreased from 2.0 mg N(2)O-N m(-2) at an initial EC of 0.5 dS m(-1) to 0.86 mg N(2)O-N m(-2) at 2.0 dS m(-1). At 90% WFPS, N(2)O production was 2 to 40 times greater than that at 60% WFPS and maximum N(2)O losses occurred at the highest EC level of 2.0 dS m(-1). Differences in the magnitude of gas emissions at varying WFPS were due to available substrate N and the predominance of nitrification under aerobic conditions (60% WFPS) and denitrification when oxygen was limited (90% WFPS). Differences in gas emissions at varying soil EC may be due to changes in mechanisms of adjustment to salt stress and ion toxicities by microbial communities. Direct effects of EC on microbial respiration and N(2)O emissions need to be accounted for in ecosystems models for predicting soil greenhouse gas emissions.

The contribution of nitrogen transformation processes to total N2O emissions from soils used for intensive vegetable cultivation

“…3). Positive correlation between N 2 O and EC has been reported previously (Amos et al 2005;Adviento-Borbe et al 2006). These correlations reinforce what is known about the relationships of certain soil indigenous parameters (i.e., acidification and salinity) and high N 2 O emission.…”

“…The rates at which these processes promote N 2 O release depend not only on environmental factors, such as temperature (Kesik et al 2006), soil pH (Stevens et al 1997;Mørkved et al 2007), organic matter content (Hayakawa et al 2009) and soil texture (Ruser et al 2006;Beare et al 2009), but also agricultural managements, including crop type (Yang and Cai 2005) and fertiliser addition (Cai et al 1997;Meng et al 2005). These factors, both individually and via interactions, can significantly affect N 2 O emissions, primarily by altering the N 2 O production processes and N 2 O product ratios of both nitrification (N 2 O/(NO 2 -+NO 3 -)) and denitrification (N 2 O/(N 2 O+N 2 )) (Martikainen and De Boer 1993;Stevens et al 1997;De Boer and Kowalchuk 2001;Khalil et al 2004;Adviento-Borbe et al 2006;Mørkved et al 2007). It has been reported that high amounts of N fertiliser in vegetable fields lead to transient and localized changes in soil physical, chemical and biochemical characteristics.…”

Leaf gas exchange in cowpea and CO2 efflux in soil irrigated with saline water

“…Adviento-Borbe et al (2006), analyzing the effect of four levels of soil electrical conductivity (ECs) -0.5, 1.0, 1.5 and 2.0 dS m -1 -on soil microbial respiration, observed that this variable was reduced with the increase in electrical conductivity, mainly because of the osmotic stress. Yuan et al (2007), studying eleven soils with EC varying from 0.32 to 23.05 dS m -1 , aiming to account for the effects of salinity on the size, activity and structure of the community of soil microorganisms in arid soils in a Chinese province, observed a negative exponential relationship between the EC and the carbon of the microbial biomass, nitrogen of the microbial biomass and basal respiration of the soil.…”

Nitrous oxide fluxes and dissolved N gases (N2 and N2O) within riparian zones along the agriculturally impacted San Joaquin River

“…N 2 O fluxes generally increase with increasing soil moisture (Adviento-Borbe et al 2006;Liu et al 2007), but moisture content associated with maximum N 2 O fluxes are reported between 30 and 80 % water-filled pore space (Granli and Bockman 1994;Ciarlo et al 2007). In addition, other microbial processes can contribute to N 2 O production, including nitrification and nitrifier denitrification (Kaplan 1983;Wrage et al 2001).…”