Methodology for Measuring Greenhouse Gas Emissions from Agricultural Soils Using Non-isotopic Techniques

Abstract

Several approaches exist for measuring greenhouse gases (GHGs), mainly CO2, N2O, and CH4, from soil surfaces. The principle methods that are used to measure GHG from agricultural sites are chamber-based techniques. Both open and closed chamber techniques are in use; however, the majority of field applications use closed chambers. The advantages and disadvantages of different chamber techniques and the principal steps of operation are described. An important part of determining the quality of the flux measurements is the storage and the transportation of the gas samples from the field to the laboratory where the analyses are carried out. Traditionally, analyses of GHGs are carried out via gas chromatographs (GCs). In recent years, optical analysers are becoming increasingly available; these are user-friendly machines and they provide a cost-effective alternative to GCs. Another technique which is still under development, but provides a potentially superior method, is Raman spectroscopy. Not only the GHGs, but also N2, can potentially be analysed if the precision of these techniques is increased in future development. An important part of this chapter deals with the analyses of the gas concentrations, the calculation of fluxes, and the required safety measures. Since non-upland agricultural lands (i.e. flooded paddy soils) are steadily increasing, a section is devoted to the specificities of GHG measurements in these ecosystems. Specialised techniques are also required for GHG measurements in aquatic systems (i.e. rivers), which are often affected by the transfer of nutrients from agricultural fields and therefore are an important indirect source of emission of GHGs. A simple, robust, and more precise methodof ammonia (NH3) emission measurement is also described.

Soil Nitrous Oxide Emissions Following Crop Residues Management in Corn-Wheat Rotation Under Conventional and No-Tillage Systems

“…During corn-wheat crop rotation, N 2 O emissions ranged from 0 to 375 and from 0 to 44 μg m -2 h -1 in residue treatments under NT and CT systems, respectively (Figures 1A and 2A). Large variability in N 2 O emissions has also been reported since production and emission of N 2 O occur through the activity of numerous groups of soil microbiota, various microbial processes (denitrification, nitrification, and chemodenitrification), agricultural practices, and soil conditions (Grant & Pattey, 2003; Hénault et al, 2012; Ma, Sun et al, 2013; Ussiri et al, 2009; Zaman et al, 2021). Also, successive periods of drying and wetting cycles as a result of irrigation and rainfall events were among the other causes of fluctuations in N 2 O emissions.…”

“…The rate of N 2 O emissions was increased after fertilization events (Figures 1 and 2) due to the abundant availability of substrate for nitrification and denitrification. The reason for the increase in N 2 O emissions after fertilization is the provision of N as one of the essential components for the production and release of N 2 O (Zaman et al, 2021), and it was justified by the positive and strong correlation of N 2 O emissions with the ammonium and nitrate (Table 1, Figures 1 and 2).…”

“…Furthermore, in the current study, soil texture type in the NT system (clay loam) could also be another reason for higher N 2 O emissions compared to that in the CT system (soil texture: sandy loam). The existence of more capillary pores in finer textured soils than in light-textured soil helps them to retain soil water more strongly and create and maintain long-term anaerobic conditions which consequently led to higher emissions of N 2 O than in sandy soils (Bouwman et al, 2002; Lesschen et al, 2011; Parton et al, 1996; Stehfest & Bouwman, 2006; Weier et al, 1993; Zaman et al, 2021). Soil texture influences N 2 O emissions due to its effect on aerobic or anaerobic conditions, microbial population, and availability of nitrogen and soil organic carbon (Charles et al, 2017; Lesschen et al, 2011; Meurer et al, 2016; Wang et al, 2021; Xu et al, 2013).…”

“…Especially, nitrous oxide is considered a potent GHGs because of its greater global warming potential (298 more powerful than CO 2 ) (Collins et al, 2017; IPCC, 2007). The N 2 O is a long-lived radiatively active greenhouse gas with an atmospheric lifetime of 114 ± 10 years and the major source of ozone-depleting reactions (Prather & Hsu, 2010; Ussiri & Lal, 2012; Zaman et al, 2021). Soil N 2 O emissions are highly heterogeneous in space and time, given their association with both climatic factors and agricultural management practices (Brown et al, 2001; Rodrigo-Comino et al, 2022).…”

Co-application of biochar and compost with decreased N fertilizer reduced annual ammonia emissions in wetland rice

“…Field measurements of NH 3 were conducted during January 2020-November 2021 in the rice field. A low-cost chamber was deployed in field conditions for NH 3 volatilization measurements (Nichols et al, 2018) and used for monitoring NH 3 fluxes in crop fields (Martins et al, 2021a,b;Zaman et al, 2021). The open chamber method was used to measure NH 3 fluxes in the field site on a daily basis.…”