The Mechanisms of High N₂O Emissions from Greenhouse Vegetable Field Soils

Abstract

Vegetable cultivation in China is characterized by high N application rate, multiple cropping, and frequent irrigation, which may have caused high N 2 O emission. However, the N 2 O emission characteristics and the underlying mechanisms responsible for N 2 O emission under high N application rate in the greenhouse vegetable field soils remains largely unknown. Thus, we conducted a field experiment to monitor N 2 O emissions using static chamber and gas chromatography techniques. Meanwhile, an incubation experiment was carried out to quantify soil gross N transformation rates and N 2 O emissions pathways via 15 N tracing and N 2 O source partitioning methods, respectively. The experiment involved three treatments: conventional farmland cultivated with soybean (CF), greenhouse vegetable field receiving only chemical N fertilizer (CGV), and greenhouse vegetable field receiving both organic manure and chemical N fertilizer (OGV). Our results showed that soil N 2 O emissions in the greenhouse vegetable fields, especially in OGV treatment, were significantly higher than those in CF treatment. Heterotrophic nitrification was the dominant pathway for N 2 O emissions accounting for up to 84.0% of the total N 2 O flux. The gross heterotrophic nitrification rate was 19.52 mg N kg À1 per day (accounting for 81% of the total nitrification rate) in OGV treatment, which was significantly higher than in CGV and CF treatment. As a consequence, the application of nitrification inhibitors might not be an effective mitigation options of N 2 O emissions from the greenhouse vegetable fields in China.Abbreviations: CF, conventional farmland; CGV, chemical N fertilization treatment greenhouse vegetable field; GC, gas chromatography; HIP, "hole-in-the pipe" model; OGV, organic manure and chemical N fertilizers treatment greenhouse vegetable field; SOC, soil organic carbon; WFPS, water-filled pore space.(1 of 9) 1600210

Reduction in N2O Emissions and Improvement in Nitrifier and Denitrifier Communities through Bamboo-Biochar-Based Fertilization in Pomelo Orchard Soil

“…This study revealed that urea application alone significantly promoted soil N 2 O emissions. The factors controlling soil N 2 O emissions include soil nitrogen concentration, nitrogentransforming functional microorganisms, appropriate soil temperature, and soil aeration performance [32][33][34][35]. The effect of N fertilizer application on N 2 O emissions was significant and was also verified in this study.…”

Increasing the Environmental Sustainability of Greenhouse Vegetable Production by Combining Biochar Application and Drip Fertigation—Effects on Soil N2O Emissions and Carbon Sequestrations

“…Reduced N fertilizer application and lowered soil moisture during the growing season explain the differences in soil N 2 O emissions between greenhouse vegetable systems managed by drip fertigation compared with those managed by over fertilization and flood irrigation [8,15,52]. Based on the structure equation modelling analysis, the significant positive direct effect (standardized path coefficients 0.52, p < 0.001, Figure 4) of soil NH 4 + -N concentration on N 2 O emissions indicated that the N 2 O emissions in this drip fertigation systems were primed by the availability of inorganic N, and by nitrification rather than by coupled nitrification-denitrification [52][53][54], as soil moisture levels stayed lower. In contrast, N 2 O emissions were driven by both nitrification and denitrification in the conventional systems managed with over fertilization and flood irrigation [55].…”

“…During the WS growing seasons, the mitigation effects on N 2 O emissions of biochar or straw mainly occurred within 10 days after basal fertigation (Figure 3b), when the soil environment condition was conducive to nitrifier and denitrifier activity [28,52]. Firstly, the significant reduction in N 2 O emission fluxes with biochar incorporation compared with DIF is related to its large specific surface and porosity, meaning lower availability of NH 4 + -N and dissolved organic carbon for microbial nitrification and denitrification [38,39].…”

Research Hotspots and Trends of Nitrification Inhibitors: A Bibliometric Review from 2004–2023

“…A comprehensive review of 491 observations from 84 publications revealed that heterotrophic nitrification contributes significantly to NO 3 production, with percentages of 24%, 32%, and 43% in forest, farmland, and grassland soils, respectively [115]. In specific environments like acidic soils found in subtropical forests [116], greenhouse vegetable fields [117], and dairy farms [118], heterotrophic nitrification can even surpass autotrophic nitrification. Unfortunately, current nitrification inhibitors only target autotrophic nitrification, neglecting the heterotrophic aspect.…”