Global evaluation of inhibitor impacts on ammonia and nitrous oxide emissions from agricultural soils: A meta‐analysis

Abstract

Inhibitors are widely considered an efficient tool for reducing nitrogen (N) loss and improving N use efficiency, but their effectiveness is highly variable across agroecosystems. In this study, we synthesized 182 studies (222 sites) worldwide to evaluate the impacts of inhibitors (urease inhibitors [UI], nitrification inhibitors [NI] and combined inhibitors) on crop yields and gaseous N loss (ammonia [NH3] and nitrous oxide [N2O] emissions) and explored their responses to different management and environmental factors including inhibitor application timing, fertilization regime, cropping system, water management, soil properties and climatic conditions using subgroup meta‐analysis, meta‐regression and multivariate analyses. The UI were most effective in enhancing crop yields (by 5%) and reducing NH3 volatilization (by 51%), whereas NI were most effective at reducing N2O emissions (by 49%). The application of UI mitigates NH3 loss and increases crop yields especially in high NH3‐N loss scenarios, whereas NI application would minimize the net N2O emissions and the resultant environmental impacts especially in low NH3‐N loss scenarios. Alternatively, the combined application of UI and NI enables producers to balance crop production and environmental conservation goals without pollution tradeoffs. The inhibitor efficacy for decreasing gaseous N loss was dependent upon soil and climatic conditions and management practices. Notably, both meta‐regression and multivariate analyses suggest that inhibitors provide a greater opportunity for reducing fertilizer N inputs in high‐N‐surplus systems and presumably favor crop yield enhancement under soil N deficiency situations. The pursuit of an improved understanding of the interactions between plant‐soil‐climate‐management systems and different types of inhibitors should continue to optimize the effectiveness of inhibitors for reducing environmental losses while increasing productivity.

Enhanced-Efficiency Fertilizers Impact on Nitrogen Use Efficiency and Nitrous Oxide Emissions from an Open-Field Vegetable System in North China

“…The performance of CUNI for increasing NUE was more consistent than CU in this study ( Table 1 ). This was probably owing to the effective reduction in N 2 O without triggering the tradeoff between NH 3 and N 2 O emissions, as the N fertilizers were less susceptible to NH 3 losses when incorporated into soil [ 35 ]. Contrary to previously reported findings by Suter et al [ 46 ], the EENF treatments (except for CUNI in 2018) did not further improve the NUE of lettuce system compared to OPT ( Table 1 ), which was probably due to the limited capacity of EENFs for promoting N uptake in this study ( Figure 1 ).…”

“…Previous meta-analyses reported that the CRFs and nitrification inhibitors (NIs) could significantly reduce the soil N 2 O emissions by 19–74% and 33–58%, respectively [ 32 , 33 ]. Additionally, the surplus N in soil is found to directly impact the EENF effectiveness, and EENFs provide a greater opportunity for reducing fertilizer N inputs and N 2 O losses in high-N-surplus cropping systems [ 34 , 35 ]. Therefore, it is critical to establish an optimal EENF application strategy specifically targeting the Chinese open-field vegetable systems.…”

Complete Issue

“…The specific products demonstrated to have such efficacy are nitrification inhibitors and polymer coatings applied to urea. Across a wide range of soils and cropping systems globally, measured nitrous oxide emission reductions averaged 49% for nitrification inhibitors (from 422 observations), 31% for combined urease and nitrification inhibitors (from 118 observations), and 19% for polymer-coated urea (from 89 comparisons) (Fan et al, 2022;Thapa et al, 2016). These reductions in nitrous oxide emissions are larger than the reported effects of these products on crop yield or NUE (7.5 and 12.9%, respectively;Abalos et al, 2014).…”

What’s the Scope of 4R Practices for Reducing Emissions from Fertilizer?

“…The specific products demonstrated to have such efficacy are nitrification inhibitors and polymer coatings applied to urea. Across a wide range of soils and cropping systems globally, measured nitrous oxide emission reductions averaged 49% for nitrification inhibitors (from 422 observations), 31% for combined urease and nitrification inhibitors (from 118 observations), and 19% for polymer‐coated urea (from 89 comparisons) (Fan et al., 2022; Thapa et al., 2016). These reductions in nitrous oxide emissions are larger than the reported effects of these products on crop yield or NUE (7.5 and 12.9%, respectively; Abalos et al., 2014).…”