Synergistic effects of diazotrophs and arbuscular mycorrhizal fungi on soil biological nitrogen fixation after three decades of fertilization

Abstract

Biological nitrogen (N) fixation (BNF) via diazotrophs is an important ecological process for the conversion of atmospheric N to biologically available N. Although soil diazotrophs play a dominant role in BNF and arbuscular mycorrhizal fungi (AMF) serve as helpers to favor BNF, the response of soil BNF and diazotrophic communities to different long-term fertilizations and the role of AMF in diazotrophs-driven BNF are poorly understood. Herein, a 33-year fertilization experiment in a wheat-maize intercropping system was conducted to investigate the changes in soil BNF rates, diazotrophic and AMF communities, and their interactions after long-term representative fertilization (chemical fertilizer, cow manure, wheat straw, and green manure). We found a remarkable increase in soil BNF rates after more than three decades of fertilization compared with nonfertilized soil, and the green manure treatment rendered the highest enhancement. The functionality strengthening was mainly associated with the increase in the absolute abundance of diazotrophs and AMF and the relative abundance of the key ecological cluster of Module #0 (gained from the co-occurrence network of diazotrophic and AMF species) with dominant diazotrophs such as Skermanella and Azospirillum. Furthermore, although the positive correlations between diazotrophs and AMF were reduced under long-term organic fertilization regimes, green manuring could reverse the decline within Module #0, and this had a positive relationship with the BNF rate. This study suggests that long-term fertilization could promote N fixation and select specific groups of N fixers and their helpers in certain areas. Our work provides solid evidence that N fixation and certain groups of diazotrophic and AMF taxa and their interspecies relationship will be largely favored after the fertilized strategy of green manure.

PGPB and/or AM Fungi Consortia Affect Tomato Native Rhizosphere Microbiota

“…Rhodocytophaga is a genus often associated with soils with high organic matter content and high salinity [ 49 ]. Skermanella can behave as a mycorrhizal helper bacterium, occurring especially where the number of AM fungal propagules is high [ 50 ].…”

Patterns and drivers of microbiome in different rock surface soil under the volcanic extreme environment

“…Performing microbial co-occurrence ecological network analyses can enhance our understanding of complex microbial communities [24,25]. According to previous studies, various environmental factors, such as soil pH, protein, and nutrients, can affect the microbial community structure, especially in extreme environments [26].…”

Soil Microorganisms in Agricultural Fields and Agronomic Regulation Pathways

“…Soil microorganisms interacting with crops play a pivotal role in promoting crop growth, increasing yield, and enhancing resilience to abiotic stress (Figure 1). Research has indicated that soil nitrogen-fixing bacteria can enhance crop growth by immobilizing atmospheric nitrogen and engaging in mutual recognition and molecular communication with legume crops [14,20]. Conversely, crops actively recruit and shape inter-root microbial communities through root secretions including sugars, phenolics, amino acids, and ketones, which serve as nutrients for beneficial microorganisms, thereby fostering optimal conditions for crop growth [10,21].…”

“…For example, nitrogen-fixing microorganisms facilitate ammonium uptake by leguminous crops through symbiosis, while diffused ammonium enriches the surrounding soil, benefiting other microorganisms. Simultaneously, nitrifying microorganisms (such as Skermanella and Azospirillum) convert ammonium into gaseous nitrogen compounds, which are released into the atmosphere [14,27]. Phosphorus, a limiting nutrient in agricultural soils, exhibits low mobility.…”

“…For example, soil tillage mechanically destroys and reconstructs the original soil, leading to changes in soil aggregates, bulk density, porosity, organic matter content, and other environmental factors that affect soil microorganisms [11][12][13]. Crop diversification alters soil microbial populations through variation in root secretions [3,9,14]. Fertilizer usage modifies the soil nutrient environment and affects the soil microbes [15,16].…”