Impact of soil amendments on nitrous oxide emissions and the associated denitrifying communities in a semi-arid environment

Abstract

Denitrifying bacteria produce and utilize nitrous oxide (N2O), a potent greenhouse gas. However, there is little information on how organic fertilization treatments affect the denitrifying communities and N2O emissions in the semi-arid Loess Plateau. Here, we evaluated how the denitrifying communities are responsible for potential denitrification activity (PDA) and N2O emissions. A field experiment was conducted with five fertilization treatments, including no fertilization (CK), mineral fertilizer (MF), mineral fertilizer plus commercial organic fertilizer (MOF), commercial organic fertilizer (OFP), and maize straw (MSP). Our result showed that soil pH, soil organic carbon (SOC), and dissolved organic nitrogen (DON) were significantly increased under MSP treatment compared to MF treatment, while nitrate nitrogen (NO3−−N) followed the opposite trend. Organic fertilization treatments (MOF, OFP, and MSP treatments) significantly increased the abundance and diversity of nirS- and nosZ-harboring denitrifiers, and modified the community structure compared to CK treatment. The identified potential keystone taxa within the denitrifying bacterial networks belonged to the distinct genera. Denitrification potentials were significantly positively correlated with the abundance of nirS-harboring denitrifiers, rather than that of nirK- and nosZ-harboring denitrifiers. Random forest modeling and structural equation modeling consistently determined that the abundance, community composition, and network module I of nirS-harboring denitrifiers may contribute significantly to PDA and N2O emissions. Collectively, our findings highlight the ecological importance of the denitrifying communities in mediating denitrification potentials and the stimulatory impact of organic fertilization treatments on nitrogen dynamics in the semi-arid Loess Plateau.

Nitrogen fertilization promoted microbial growth and N2O emissions by increasing the abundance of nirS and nosZ denitrifiers in semiarid maize field

“…This suggests their high soil nutrient cycling and impact on the functional aspects of denitrification processes ( Cui et al, 2016 ; Ouyang et al, 2018 ; Huang et al, 2020b ). Substantially SOC and NO 3 − -N in optimal N fertilization emerged as a significant factor contributing to the elevation of denitrifier gene copies ( Tao et al, 2018 ; Fudjoe et al, 2022 ). Various nitrogen fertilizer rates and environmental factors exerted distinct effects on the diversity of denitrifying communities associated with nirS and nosZ , underscoring their specialized enhancement linked to specific ecological niches that lead to heightened species richness ( Yoshida et al, 2009 ; Jang et al, 2018 ; Shi et al, 2019 ).…”

“…The increase in SOC and DON under different nitrogen fertilizer rate treatments underscored the significant contribution of the nirS denitrifying community to N 2 O emissions ( Sun et al, 2017 ; Tao et al, 2018 ). Cupriavidus possesses metabolic pathways that utilize SOC and NO 3 − -N as alternative electron acceptors ( Fudjoe et al, 2022 ). In alkaline soil, the genus Rhodanobacter facilitates nitrogen losses during denitrification ( Ma et al, 2018 ).…”

“…In the bulk soil, the main genera within the nosZ denitrifying communities under N2 and N3 treatments were Mesorhizobium , Azospirillum , and Herbaspirillum . Specifically, genera Mesorhizobium and Azospirillum were pivotal for nitrogen fixation, playing a vital role in the production of nutrient biomolecules such as organic compounds, enzymes, adenosine phosphate groups, and polynucleotides ( Huang et al, 2020a ; Fudjoe et al, 2022 ). The usage of nitrogen fertilizers resulted in the decomposition of available nutrients such as SOC and NO 3 − -N in the rhizosphere soil resulting in the notable prevalence of the genus Rhizobium , Burkholderia , and Microvirga among denitrifiers containing nosZ .…”

“…The study reveals that climatic conditions are crucial in determining N 2 O emission rates. The growth rate of crops, soil microbial activity, and nitrogen cycling in the soil is substantially impacted by factors such as soil temperature and moisture conditions ( Peng et al, 2018 ; Fudjoe et al, 2022 ). Plastic mulch increased soil moisture and temperature (ranging from 21 to 31°C), leading to variations in drying and wetting cycles within the same period (June and July).…”

“…The complex soil population consists of diverse microbial communities that play a vital role in the dynamic global ecology ( Mamet et al, 2019 ). Hence, employing a network-based approach proves valuable in examining the connections between microbial communities and ecological factors, thereby identifying potential keystone species that contribute significantly to carbon and nitrogen cycling ( Barberán et al, 2012 ; Fudjoe et al, 2022 ). Keystone taxa are essential for maintaining coherence and enhancing the performance of microbial communities ( Williams et al, 2014 ; Chen et al, 2019a ).…”