Direct Nitrous Oxide Emissions From Tropical And Sub-Tropical Agricultural Systems - A Review And Modelling Of Emission Factors

Abstract

There has been much debate about the uncertainties associated with the estimation of direct and indirect agricultural nitrous oxide (N2O) emissions in developing countries and in particular from tropical regions. In this study, we report an up-to-date review of the information published in peer-review journals on direct N2O emissions from agricultural systems in tropical and sub-tropical regions. We statistically analyze net-N2O-N emissions to estimate tropic-specific annual N2O emission factors (N2O-EFs) using a Generalized Additive Mixed Model (GAMM) which allowed the effects of multiple covariates to be modelled as linear or smooth non-linear continuous functions. Overall the mean N2O-EF was 1.2% for the tropics and sub-tropics, thus within the uncertainty range of IPCC-EF. On a regional basis, mean N2O-EFs were 1.4% for Africa, 1.1%, for Asia, 0.9% for Australia and 1.3% for Central & South America. Our annual N2O-EFs, estimated for a range of fertiliser rates using the available data, do not support recent studies hypothesising non-linear increase N2O-EFs as a function of applied N. Our findings highlight that in reporting annual N2O emissions and estimating N2O-EFs, particular attention should be paid in modelling the effect of study length on response of N2O.

Soil pH as the chief modifier for regional nitrous oxide emissions: New evidence and implications for global estimates and mitigation

“…Also, a meta‐analysis by Albanito et al. () did not support a nonlinear response of N 2 O emission to N fertilization. A possible explanation for this discrepancy is that N 2 O ∆EFs may differ with environmental factors and cancel each other out when data from different regions were collated.…”

“…Besides environmental factors highlighted in previous analysis, also other factors may modify N 2 O emission (Albanito et al, 2017;Gerber et al, 2016;Liu et al, 2017;Rashti et al, 2015;Stehfest & Bouwman, 2006;Zhou et al, 2015Zhou et al, , 2017 and thus influence our results. For example, soil N 2 O emissions usually vary significantly with agricultural managements, such as fertilizer type (Burton, Li, & Grant, 2008;Gao, Asgedom, Tenuta, & Flaten, 2015;Lebender, Senbayram, Lammel, & Kuhlmann, 2014;Zhou et al, 2017), application mode and time (Burton, Zebarth, Gillam, & MacLeod, 2008;Halvorson & Del Grosso, 2013;Tenuta, Gao, Flaten, & Amiro, 2016), crop type (Gerber et al, 2016), irrigation pattern (Han et al, 2017; S anchez-Mart ın, Arce, Benito, Garcia-Torres, & Vallejo, 2008), and tillage practice (Liu, Mosier, Halvorson, & Zhang, 2005).…”

Re-assessing nitrous oxide emissions from croplands across Mainland China

“…From the collected literature, data pairs of N2O emissions under a fertilizer treatment and a nonfertilized control were retrieved and archived, retaining a total of 71 studies. In addition, 33 studies meeting our criteria in the dataset used by Albanito et al (2017) were checked and added to the primary dataset. Finally, a dataset comprising 853 data pairs from a total of 104 studies were constructed and used in this study.…”

“…An issue of uncertainty may have arisen with annual average data of temperature and precipitation of the study locations as crop seasonal temperature and precipitation were not reported in most the studies. Moreover, for the absence of multiyear information in our dataset though estimation of annual emissions may vary with experiment length (Albanito et al, 2017). In addition, average data from large scale observations were used in cases where local data were missing, rising the uncertainties for our model.…”

Vergelijking klimaateffecten van de gangbare vs. de biologische landbouw

“…Het gebruik van compost leidde vervolgens tot de minste N2O-emissie, waarbij wel moet worden opgemerkt dat mogelijk N2O vrijgekomen is bij het produceren van de compost (Bos et al 2017). Het is sowieso belangrijk om, als N2O emissies worden gerapporteerd en emissiefactoren worden geschat, meer rekening te houden met het effect van de lengte van de studie op de respons van N2O (Albanito et al 2017). …”