Linkage of N₂O emissions to the abundance of soil ammonia oxidizers and denitrifiers in purple soil under long-term fertilization

Abstract

Microbial nitrification and denitrification are responsible for the majority of soil nitrous (N 2 O) emissions. In this study, N 2 O emissions were measured and the abundance of ammonium oxidizers and denitrifiers were quantified in purple soil in a long-term fertilization experiment to explore their relationships. The average N 2 O fluxes and abundance of the amoAgene in ammonia-oxidizing bacteria during the observed dry season were highest when treated with mixed nitrogen, phosphorus and potassium fertilizer (NPK) and a single N treatment (N) using NH 4 HCO 3 as the sole N source; lower values were obtained using organic manure with pig slurry and added NPK at a ratio of 40%:60% (OMNPK),organic manure with pig slurry (OM) and returning crop straw residue plus synthetic NH 4 HCO 3 fertilizer at a ratio of 15%:85% (SRNPK). The lowest N 2 O fluxes were observed in the treatment that used crop straw residue(SR) and in the control with no fertilizer (CK). Soil NH 4 + provides the substrate for nitrification generating N 2 O as a byproduct. The N 2 O flux was significantly correlated with the abundance of the amoA gene in ammonia-oxidizing bacteria (r = 0.984, p < 0.001), which was the main driver of nitrification. During the wet season, soil nitrate (NO 3 − ) and soil organic matter (SOC) were found positively correlated with N 2 O emissions (r = 0.774, p = 0.041 and r = 0.827, p = 0.015, respectively). The nirS gene showed a similar trend with N 2 O fluxes. These results show the relationship between the abundance of soil microbes and N 2 O emissions and suggest that N 2 O emissions during the dry season were due to nitrification, whereas in wet season, denitrification might dominate N 2 O emission.

How Tillage and Fertilization Influence Soil N2O Emissions after Forestland Conversion to Cropland

“…+ and NO 3 − concentrations after mineral N fertilizer application to the croplands (Figure 3a,b). The high NH 4 + and NO 3 − concentrations following fertilization directly provide sufficient substrates for nitrification and denitrification and thus significantly stimulate soil N 2 O emissions [8,11,20,23]. This phenomenon has been reported in many previous studies on different croplands [5,10,43].…”

“…On the other hand, good soil aeration condition accelerated the gas exchange between soil and atmosphere, which could promote the diffusivity of N 2 O from soil into atmosphere [3,14]. Application of mineral N fertilizer could directly increase soil inorganic N concentrations (Figure 3), providing substrates for the two main N 2 O production processes of nitrification and denitrification [8,9,28]. In this study, the N 2 O flux from the croplands all showed pulse emissions following tillage and N fertilization events (Figure 4a), thus resulted in much greater cumulative N 2 O emissions compared to the forestland (Table 3).…”

“…To guarantee a secure food supply for global human population growth, agriculture intensification might cause more N 2 O emission increases in the future [4,5]. Soil N 2 O is mainly produced by microbial nitrification and denitrification [6,7], and strongly affected by substrate availability (e.g., NH 4 + and NO 3 − concentrations) and environmental conditions (e.g., temperature and moisture) [6,[8][9][10][11].…”

“…Grandy and Robertson reported that in initial cultivation, tillage practices significantly disturbed the soil structure and released large amounts of organic C and N from macroaggregates, thus accelerating the soil N 2 O fluxes [18]. Fertilization has been widely understood to significantly increase N 2 O emissions, mainly through supplying more inorganic N concentrations and sufficient substrates (NH 4 + and NO 3 − ) for nitrification and denitrification [8,11,[23][24][25]. Bouwman et al analyzed 139 N 2 O studies from agricultural regions and found that N 2 O emissions generally increase with N application rates, especially above the application rates of 100 kg N ha −1 [26].…”

Spatial and temporal dynamics of the microbial communities in soils cultivated with sugarcane

“…Overall, there is no dominant driver connected to variations of different microbial communities across the crop systems.Then, we can argue that better understanding of the link between the most significant drivers with the microbial community across the crop systems may be achieved using mathematical modeling based on ecological theories (see Wade et al, 2016;Prosser et al, 2007). The application of nitrogen, phosphorus and potassium fertilizer increased the N 2 O emission (Dong et al, 2015) Wheat…”