Insight into the functional mechanisms of nitrogen-cycling inhibitors in decreasing yield-scaled ammonia volatilization and nitrous oxide emission: A global meta-analysis

Abstract

Soil ammonia (NH₃) volatilization and nitrous oxide (N₂O) emission decrease nitrogen (N) utilization efficiency and cause some environmental problems. The N-cycling inhibitors are suggested to apply to enhance N utilization efficiency. Quantifying effects of N-cycling inhibitors on yield-scaled NH₃ volatilization and N₂O emission and functional genes could provide support for the optimal selection and application of N-cycling inhibitor. We conducted a meta-analysis to reveal the effects of N-cycling inhibitors on soil abiotic properties, functional genes and yield-scaled NH₃ volatilization and N₂O emission by extracting data from 166 published articles and linked their comprehensive relationships. The N-cycling inhibitors in this meta-analysis mainly includes nitrification inhibitors 3, 4-dimethyl pyrazole phosphate, dicyandiamide and 2-chloro-6-trichloromethylpyridine, urease inhibitor N-(n-butyl) thiophosphoric triamide and biological nitrification inhibitors methyl 4-hydroxybenzoate and 1, 9-decanediol. The N-cycling inhibitor applications significantly increased alkaline soil pH but significantly decreased acidic soil pH. The N-cycling inhibitors decreased soil AOB amoA gene abundances mostly under the condition of pH 4.5-6 (mean: 212%, 95% confidence intervals (CI): 249% and -176%) and significantly decreased nirS gene (mean: 39%; 95% CI: 72% and -6%). The yield-scaled NH₃ volatilization was significantly decreased by the N-cycling inhibitors under the condition of soil pH = 7-8.5 (mean: 45%; 95% CI: 59% and -31%). The yield-scaled N₂O emission was also significantly reduced by all N-cycling inhibitors and had negative correlations with the soil nirK and nirS gene abundances. The effects of N-cycling inhibitors on soil pH, ammonium-N, nitrate-N and nitrifying and denitrifying genes and yield-scaled NH₃ volatilization and N₂O emission were dominated by the inhibitor types, soil textures, crop species and environmental pH. Our study could provide technical support for the optimal selection and application of N-cycling inhibitor under different environmental conditions.

Keywords: Global meta-analysis; N-cycling inhibitors; Nitrifying and denitrifying genes; Yield-scaled N(2)O emission; Yield-scaled NH(3) volatilization.