Nitrification inhibitors can increase post-harvest nitrous oxide emissions in an intensive vegetable production system

Abstract

To investigate the effect of nitrification inhibitors (NIs) 3,4-dimethylpyrazole phosphate (DMPP) and 3-methylpyrazole 1,2,4-triazole (3MP + TZ), on N2O emissions and yield from a typical vegetable rotation in sub-tropical Australia we monitored soil N2O fluxes continuously over an entire year using an automated greenhouse gas measurement system. The temporal variation of N2O fluxes showed only low emissions over the vegetable cropping phases, but significantly higher emissions were observed post-harvest accounting for 50–70% of the annual emissions. NIs reduced N2O emissions by 20–60% over the vegetable cropping phases; however, this mitigation was offset by elevated N2O emissions from the NIs treatments over the post-harvest fallow period. Annual N2O emissions from the conventional fertiliser, the DMPP treatment, and the 3MP + TZ treatment were 1.3, 1.1 and 1.6 (sem = 0.2) kg-N ha−1 year−1, respectively. This study highlights that the use of NIs in vegetable systems can lead to elevated N2O emissions by storing N in the soil profile that is available to soil microbes during the decomposition of the vegetable residues. Hence the use of NIs in vegetable systems has to be treated carefully and fertiliser rates need to be adjusted to avoid an oversupply of N during the post-harvest phase.

Microplastic fibers affect dynamics and intensity of CO2and N2O fluxes from soil differently

“…this is necessary to obtain precise results for trace gas emissions 28,[68][69][70][71][72] . Future endeavors aimed at quantifying trace gas flux responses to microplastic addition should also rely on such measurements.…”

Opportunities to improve nitrogen use efficiency in an intensive vegetable system without compromising yield

“…However, this can also decrease the marketable yield for some vegetable crops (Di Mola et al., 2020), so farmers may be reluctant to adopt this strategy. Use of the nitrification inhibitor 3,4‐dimethylpyrazole phosphate (DMPP) has been effective at reducing N 2 O emissions from applied fertilizer‐N in vegetable systems (Lam et al., 2018), but the impact on NUE and vegetable yield is not guaranteed (Pfab et al., 2012; Scheer et al., 2017). Rose et al.…”

Global Research Alliance N2O chamber methodology guidelines: Guidelines for gap‐filling missing measurements

“…Emission peaks typically make up a considerable portion of annual emissions: up to 90% for freeze–thaw emissions (Wagner‐Riddle et al., 2017), up to 97% postharvest and after summer rainfall in semiarid regions (Barton, Hoyle, Stefanova, & Murphy, 2016), up to 50% within the first weeks after N fertilizer events (Shcherbak et al., 2014), and up to 30% within a few weeks of manure application (Chadwick et al., 2011). Peak events have also been observed during tillage, residue management (Scheer et al., 2017), and irrigation, though these have been less studied and often coincide with N application events.…”

“…With increasing gap numbers or gap duration it becomes more likely that gap‐filling will be used over periods where soil conditions and chemistry, and thus emission rates, may change—adding to uncertainty in emission estimates. Beyond the already‐mentioned challenge of underestimating emissions due to missing peak emission events, sampling strategies that do not sample outside of the growing season present issues, as they may be difficult to extrapolate to an annual value or accurate EF (Scheer et al., 2017; Wagner‐Riddle et al., 2017). Although some studies have examined the influence of sampling frequency from chamber methods on reported annual emissions (Barton et al., 2015; Mishurov & Kiely, 2011; Savage, Phillips, & Davidson, 2014), research into determining and testing gap‐filling methods has been limited (Bigaignon, Fieuzal, Delon, & Tallec, 2020; Cowan et al., 2019; De Rosa et al., 2018; Taki, Wagner‐Riddle, Parkin, Gordon, & VanderZaag, 2018; Webb et al., 2019).…”