AimsPlant yield, nitrate accumulation risk, and the potential pathogenic microorganism are critical parameters in evaluating soil fertility management. The nitrate content in the soil-plant system is substantially driven by soil abiotic properties and soil and endophytic microorganisms which are also potential resources of plant pathogenicity. This study aimed to quantify the effects of citric acid (CA), alone or with dicyandiamide (DCD) and 3, 4-dimethylpyrazole phosphate (DMPP), on plant yield, nitrate accumulation risk and potential pathogenicity of soil-plant system.MethodsOur study contained six treatments: (1) control without CA or nitrification inhibitor (CK); (2) sole DCD application treatment (DCT); (3) sole DMPP application treatment (DMT); (4) sole CA application treatment (CAT); (5) CA + DCD application treatment (CADCT) and (6) CA + DMPP application treatment (CADMT). The nitrate contents, plant yields, and bacterial communities in soil and plant samples were analyzed.ResultsThe CA significantly reduced soil nitrate contents by 29.8%. Relative to sole CA application, extra nitrification inhibitor application significantly enhanced plant yields and decreased plant nitrate contents. The exclusive CA application could significantly stimulate the soil Actinobacteriota but reduce the soil pathogenicity, but extra nitrification inhibitors led to higher potential soil pathogenicity.ConclusionsThe single CA application could decrease nitrate accumulation risk and mitigating potential soil pathogenicity damage, while extra nitrification inhibitor application would intensify the performances of CA in decreasing plant nitrate accumulation but potentially enhancing the pathogenic. It deserves to emphasize the consideration of the tradeoffs among plant yield, nitrate accumulation risk, and potential pathogen risk when evaluating the effects of CA and nitrification inhibitors.

Fertilizer-intensive agriculture leads to emissions of reactive nitrogen (Nr), posing threats to climate via nitrous oxide (N2O) and to air quality and human health via nitric oxide (NO) and ammonia (NH3) that form ozone and particulate matter (PM) downwind. Adding nitrification inhibitors (NIs) to fertilizers can mitigate N2O and NO emissions but may stimulate NH3 emissions. Quantifying the net effects of these trade-offs requires spatially resolving changes in emissions and associated impacts. We introduce an assessment framework to quantify such trade-off effects. It deploys an agroecosystem model with enhanced capabilities to predict emissions of Nr with or without the use of NIs, and a social cost of greenhouse gas to monetize the impacts of N2O on climate. The framework also incorporates reduced-complexity air quality and health models to monetize associated impacts of NO and NH3 emissions on human health downwind via ozone and PM. Evaluation of our model against available field measurements showed that it captured the direction of emission changes but underestimated reductions in N2O and overestimated increases in NH3 emissions. The model estimated that, averaged over applicable U.S. agricultural soils, NIs could reduce N2O and NO emissions by an average of 11% and 16%, respectively, while stimulating NH3 emissions by 87%. Impacts are largest in regions with moderate soil temperatures and occur mostly within two to three months of N fertilizer and NI application. An alternative estimate of NI-induced emission changes was obtained by multiplying the baseline emissions from the agroecosystem model by the reported relative changes in Nr emissions suggested from a global meta-analysis: -44% for N2O, -24% for NO and +20% for NH3. Monetized assessments indicate that on an annual scale, NI-induced harms from increased NH3 emissions outweigh (8.5-33.8 times) the benefits of reducing NO and N2O emissions in all agricultural regions, according to model-based estimates. Even under meta-analysis-based estimates, NI-induced damages exceed benefits by a factor of 1.1-4. Our study highlights the importance of considering multiple pollutants when assessing NIs, and underscores the need to mitigate NH3 emissions. Further field studies are needed to evaluate the robustness of multi-pollutant assessments.