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

Response of the nosZ-type denitrifying microbial community and metabolic characteristics to precipitation changes in the alpine wetland

The impact of climate change on the global hydrological cycle is becoming increasingly significant, with changes in precipitation patterns emerging as a key factor influencing the carbon and nitrogen cycling processes in alpine wetland ecosystems. However, the response of the nosZ-type denitrifying microbial community and its metabolic characteristics in the source wetland to precipitation changes remains unclear. In this study, high-throughput sequencing of the nosZ gene and LC-MS-based metabolomics were used to investigate the response of the nosZ-type denitrifying microbial community and its metabolic characteristics to precipitation changes (4 years) in the source wetland of Qinghai Lake. The results showed that Microvirga was the key bacterial group in the source wetland of Qinghai Lake, and Azospirillum was sensitive to changes in precipitation (P < 0.05). The 50% rainfall enhancement treatment significantly increased soil moisture, and the total carbon content showed an increasing trend with the increase in precipitation (P < 0.05). pH was the most important explanatory factor for community structure, while total nitrogen content was the key explanatory factor for community diversity. Deterministic processes dominated the assemblage of the nosZ-type denitrifying microbial community in the source wetland of Qinghai Lake. Soil metabolomics analysis showed that the differential metabolites in the Source Wetland mostly exhibited significant positive correlations. Precipitation changes significantly affected the relative abundance of N-Acetylaspartic acid. In summary, lower precipitation is more favorable for maintaining carbon storage in the source wetlands of Qinghai Lake. Precipitation variation disrupted the existing nitrogen balance within the ecosystem and altered the structure of the nosZ-type denitrifying microbial community and soil metabolic characteristics. These findings imply that climate change-driven shifts in precipitation patterns may impact carbon and nitrogen dynamics in alpine wetlands, alter ecosystem stability, and have profound effects on microbial communities and biogeochemical cycles.

Soil metagenomics reveals the effect of nitrogen on soil microbial communities and nitrogen-cycle functional genes in the rhizosphere of Panax ginseng

Nitrogen (N) is the primary essential nutrient for ginseng growth, and a reasonable nitrogen application strategy is vital for maintaining the stability of soil microbial functional communities. However, how microbial-mediated functional genes involved in nitrogen cycling in the ginseng rhizosphere respond to nitrogen addition is largely unknown. In this study, metagenomic technology was used to study the effects of different nitrogen additions (N0: 0, N1: 20, N2: 40 N g/m2) on the microbial community and functional nitrogen cycling genes in the rhizosphere soil of ginseng, and soil properties related to the observed changes were evaluated. The results showed that N1 significantly increased the soil nutrient content compared to N0, and the N1 ginseng yield was the highest (29.90% and 38.05% higher than of N0 and N2, respectively). N2 significantly decreased the soil NO3 -N content (17.18 mg/kg lower than N0) and pH. This resulted in a decrease in the diversity of soil microorganisms, a decrease in beneficial bacteria, an increase in the number of pathogenic microorganisms, and an significant increase in the total abundance of denitrification, assimilatory nitrogen reduction, and dissimilatory nitrogen reduction genes, as well as the abundance of nxrA and napA genes (17.70% and 65.25% higher than N0, respectively), which are functional genes involved in nitrification that promote the soil nitrogen cycling process, and reduce the yield of ginseng. The results of the correlation analysis showed that pH was correlated with changes in the soil microbial community, and the contents of soil total nitrogen (TN), ammonium nitrogen (NH4 +-N), and alkaline-hydrolyzed nitrogen (AHN) were the main driving factors affecting the changes in nitrogen cycling functional genes in the rhizosphere soil of ginseng. In summary, nitrogen addition affects ginseng yield through changes in soil chemistry, nitrogen cycling processes, and functional microorganisms.

Optimizing the Mulching Pattern and Nitrogen Application Rate to Improve Maize Photosynthetic Capacity, Yield, and Nitrogen Fertilizer Utilization Efficiency

Residual film pollution and excessive nitrogen fertilizer have become limiting factors for agricultural development. To investigate the feasibility of replacing conventional plastic film with biodegradable plastic film in cold and arid environments under nitrogen application conditions, field experiments were conducted from 2021 to 2022 with plastic film covering (including degradable plastic film (D) and ordinary plastic film (P)) combined with nitrogen fertilizer 0 (N0), 160 (N1), 320 (N2), and 480 (N3) kg·ha-1. The results showed no significant difference (p > 0.05) in dry matter accumulation, photosynthetic gas exchange parameters, soil enzyme activity, or yield of spring maize under degradable plastic film cover compared to ordinary plastic film cover. Nitrogen fertilizer is the main factor limiting the growth of spring maize. The above-ground and root biomass showed a trend of increasing and then decreasing with the increase in nitrogen application level. Increasing nitrogen fertilizer can also improve the photosynthetic gas exchange parameters of leaves, maintain soil enzyme activity, and reduce soil pH. Under the nitrogen application level of N2, the yield of degradable plastic film and ordinary plastic film coverage increased by 3.74~42.50% and 2.05~40.02%, respectively. At the same time, it can also improve water use efficiency and irrigation water use efficiency, but it will reduce nitrogen fertilizer partial productivity and nitrogen fertilizer agronomic use efficiency. Using multiple indicators to evaluate the effect of plastic film mulching combined with nitrogen fertilizer on the comprehensive growth of spring maize, it was found that the DN2 treatment had the best complete growth of maize, which was the best model for achieving stable yield and income increase and green development of spring maize in cold and cool irrigation areas.

Metagenomics reveals the response of desert steppe microbial communities and carbon-nitrogen cycling functional genes to nitrogen deposition

Introduction

Nitrogen (N) deposition seriously affects the function of carbon (C) and N cycling in terrestrial ecosystems by altering soil microbial communities, especially in desert steppe ecosystems. However, there is a need for a comprehensive understanding of how microorganisms involved in each C and N cycle process respond to N deposition.

Methods

In this study, shotgun metagenome sequencing was used to investigate variations in soil C and N cycling-related genes in the desert steppe in northern China after 6 years of the following N deposition: N0 (control); N30 (N addition 30 kg ha-1 year-1): N50 (N addition 50 kg ha-1 year-1).

Results

N deposition significantly increased the relative abundance of Actinobacteria (P < 0.05) while significantly decreased the relative abundances of Proteobacteria and Acidobacteria (P < 0.05). This significantly impacted the microbial community composition in desert steppe soils. The annual addition or deposition of 50 kg ha-1 year-1 for up to 6 years did not affect the C cycle gene abundance but changed the C cycle-related microorganism community structure. The process of the N cycle in the desert steppe was affected by N deposition (50 kg ha-1 year-1), which increased the abundance of the pmoA-amoA gene related to nitrification and the nirB gene associated with assimilation nitrite reductase. There may be a niche overlap between microorganisms involved in the same C and N cycling processes.

Discussion

This study provides new insights into the effects of N deposition on soil microbial communities and functions in desert steppe and a better understanding of the ecological consequences of anthropogenic N addition.