Biology and Fertility of Soils最新文献

Bacillus amyloliquefaciens is a widely used plant growth-promoting rhizobacterium. To investigate its role and mechanisms in selenium (Se) biofortification in crops, a pot experiment with four treatments including no application of Se fertilizer and B. amyloliquefaciens (control), B. amyloliquefaciens application (BA), Se fertilizer application (Se), and combined B. amyloliquefaciens and Se fertilizer application (BA + Se) was conducted. The results showed that, BA + Se treatment significantly increased total biomass of tea seedling compared with control, BA and Se treatments. Additionally, compared with Se treatment, BA + Se treatment significantly increased the Se concentrations in root and leaf, and Se content in the whole tea seedling by 101.4%, 34.5%, and 149.5%, respectively; BA + Se treatment also significantly increased the soil exchangeable Se and total available Se concentrations. Compared with control, BA treatment upregulated the expression level of CsPHT1;2b; Se treatment upregulated the expression levels of CsSULTR1;1, CsSULTR1;2, CsPHT1;2a and CsPHT1;2b; BA + Se treatment upregulated the CsSULTR1;1 and CsPHT1;2a expression levels in tea seedling roots. The 16S rRNA indicated that BA and Se treatments had no effects on the diversity of rhizosphere bacterial community, but altered bacterial community composition. Soil pH was the most important environmental factor affecting rhizosphere bacterial community composition. BA + Se treatment significantly increased soil pH and the complexity of rhizosphere bacterial symbiotic network, compared with other three treatments. Furthermore, comparative analysis about rhizosphere soil properties and bacterial community composition and function between Se and BA + Se treatments, suggested that BA + Se treatment promoted soil Se availability by recruiting g_Sinomonas species and regulating the abundance of Se reductase in the rhizosphere.

In this paper a new modeling approach for denitrification and similar processes, which depend on the geochemical gradient between the air-filled larger pores in a soil and a water-filled matrix, is presented. The new modeling approach is capable of taking soil structural properties (obtained e.g. from X-ray CT) into account without requiring a high-resolution simulation. The model approach is explained and its application is demonstrated by simulating denitrification experiments conducted with repacked soil samples to assess the challenges and possibilities of the new approach. The main result of the modeling is that the nitrous oxide emission measured in the experiment can not be explained by a limited supply with oxygen alone at a carbon turnover rate derived from carbon dioxide emissions. It is additionally necessary that the microbial activity is concentrated in localized hot spots to create anaerobic conditions. This is confirmed by analytical solutions.

Untreated chicken manure causes a large amount of antibiotics and heavy metals to enter the soil environment. Currently, there is limited research on antibiotic resistance genes (ARGs) and heavy metal resistance genes (HMRGs) in soil profile. In this study, we conducted a preliminary investigation on the soil profile of vegetable field contaminated by chicken manure. The results showed that the absolute abundance of some resistance genes was higher at the 20–60 cm. Subsequently, we further analyzed the vertical migration of bacteria bearing ARGs and HMRGs through a soil profile as affected by manure using metagenomic sequencing. The findings revealed that long-term application of chicken manure significantly increased the alpha (α) diversity of the 0–20 cm soil layer ARGs and HMRGs, the plasmids relative abundance of soil profile substantially increased. Furthermore, long-term application of chicken manure changed the community composition of the 0–20 cm soil layer resistance genes, and also affected the community composition of the 20–40 cm soil layer with the increase of manure rates. Additionally, long-term application of chicken manure significantly increased the α diversity of the 0–20 cm soil layer bacteria. Structural equation modeling (SEM) further analysis revealed that bacterial relative abundance was the primary driving factor for the distribution of ARGs in vertical space, while mobile genetic elements (MGEs) were the main driving factor for HMRGs. This study strengthens our understanding of the vertical spatial distribution of soil resistance genes following long-term application of chicken manure, and also provides the basis for the management of subterranean environment.

The recalcitrant nature of wheat (Triticum aestivum L.) straw, one of the most abundant agricultural residues, presents challenges for efficient decomposition, limiting nutrient release and organic matter retention in soils. Understanding the effects of tillage practices on wheat straw decomposition and shaping associated microbial communities is essential for enhancing microbial-mediated breakdown and optimizing residue management to enhance soil health, nutrient cycling, and sustainability in agricultural systems. In this study, the effect of different tillage practices on wheat straw decomposition and associated bacterial and fungal community compositions during non-growing and growing seasons were studied. To simulate tillage, litter bags filled with wheat straw were placed at respective soil depths for conventional (22–24 cm) and reduced (8–10 cm) tillage, and on the surface for the no-tillage treatment. The subsets of the litter bags were randomly retrieved after 145 days and at the end of the experiment after 290 days. Statistical analysis revealed that tillage treatments significantly influenced the decomposition rate and nutrient release over time. Overall, the alpha diversity of the decomposition-associated microbial community was not substantially affected by different tillage treatments, while beta diversity exhibited distinct microbial community compositions in relation to tillage practices. The results of this study contribute to a deeper understanding of wheat straw decomposition-associated bacterial and fungal communities’ response to different tillage treatments, with observations made at two distinct sampling times (non-growing and growing seasons) under certain edaphic and climatic conditions.

Little is known about how seedlings sense new soil environments and how the rhizosphere bacteriome changes accordingly. It is important to elucidate these changes to better understand feedbacks that contribute to nutrient cycling and plant fitness. Here, we explored how the tomato rhizosphere bacteriome developed weekly throughout the vegetative developmental stage and with variable nitrogen (N) fertilizer additions. Bacterial communities expressing diverse functions highly fluctuated in the first and second week after planting, and these fluctuations diminished progressively after the third week. Bacteria capable of biocontrol stabilized after the fourth week, while those involved in nutrient cycling continued to change in abundance week-to-week. Thus, bacterial specialization may be concomitant with bacteriome stabilization. With N fertilizer application, bacteria with diverse functions continued to fluctuate through the fifth week. However, regardless of fertilization, bacterial communities stabilized by the sixth week. It may take two weeks for roots to select for soil bacteria to assemble a specific rhizosphere bacteriome, but when N is applied, this period extends. Subsequently, roots may select for bacteria that are already established in the rhizosphere rather than from the bulk soil. This study showcases the dynamics of rhizosphere assemblage and how this process is affected by N additions.

Plants can modify soil properties over time through interactions with soil microorganisms, creating a legacy that may influence subsequent plant growth. This study investigates how soil vegetation covers affect growth and nutrient uptake and phosphorus (P) and nitrogen (N)use efficiencies in two eucalypt species, and the impact of new plant cultivation on soil microbial traits. Using a greenhouse microcosm experiment, we compared soils from a 20-year eucalypt plantation (Euc) and secondary vegetation (Sec) covers, cultivated for five months with Eucalyptus grandis, E. globulus, or left uncultivated. We measured plant growth, P and N concentrations, root and soil enzyme potential activities, and soil properties. Results showed that E. globulus plants in Euc soil had 23% higher shoot biomass production and 27% greater P uptake efficiency compared to plants in Sec soil. Both eucalypt species showed improved P and N use efficiencies in Euc soils, suggesting beneficial soil legacy effects. Furthermore, microbial traits related to arbuscular mycorrhizal (AM) fungi persisted partially in Sec soils, suggesting a beneficial AM fungal legacy for new eucalypt cultivation. The potential activity of enzymes associated with soil carbon and sulfur cycles was clearly influenced by plant presence, whereas enzymes related to the P cycle maintained their potential activity regardless of plant presence, indicating a lasting soil legacy for P mineralization enzymes. The results highlight the role of plant-soil feedback in nutrient utilization and suggest that soil management strategies should consider past vegetation to enhance sustainable eucalypt production.

It is widely accepted that old-aged forest can accumulate soil organic carbon (SOC). How microbial physiological traits respond to forest age and whether they drive SOC sequestration in old-aged forest remain elusive. Therefore, we compared the microbial C use efficiency (CUE), biomass turnover rate (rB), microbial biomass C (MBC) and necromass C (MNC) across soil profiles from middle and old-aged forest and evaluated how these microbial traits are related to SOC storage. The results revealed that both forests could accumulate SOC and old-aged forest supported higher SOC storage than middle-aged forest from 2005 to 2020. Moreover, SOC was concentrated on the surface soils of middle-aged forest, whereas it was more distributed across the deeper soil profile in old-aged forest. Compared with middle-aged forest, the O, A and B soil layers of old-aged forest presented increases in microbial CUE (17.8%, 36.9% and 25.0%, respectively), rB (43.7%, 39.7% and 10.8%, respectively), MBC (114.8%, 81.1% and 122.9%, respectively), and MNC content (47.0%, 22.2% and 21.6%, respectively). Random forest analysis suggested that SOC accumulation is controlled mainly by microbial physiological traits rather than other factors including environmental variables. Specifically, microbial CUE and turnover rates increased in old-aged forest, resulting in higher MBC and MNC contents, which in turn led to SOC accumulation. Moreover, the effects of plant and soil properties on SOC storage are regulated mainly by microbial-physiological parameters and the size of microbial C pools. Our findings provide valuable insights into the microbial mechanisms underlying SOC storage in old-aged forest.

Utilising the rhizosphere microbiota as a biological control agent is a promising strategy to protect plants against pathogens, although its efficacy in fungal hosts is uncertain. This study investigated the efficacy of Pseudomonas chlororaphis, a bacterial strain, in mitigating Paecilomyces penicillatus, a soil-borne pathogenic fungus responsible for white mould disease (WMD) in cultivated morels, such as Morchella importuna. Soils with chronic WMD, inoculated with or without P. chlororaphis, were utilised for M. importuna cultivation. In P. chlororaphis-inoculated morel soil beds, P. chlororaphis colonised both the mycelial surface and ascocarp matrix of M. importuna, increasing the abundance of Morchella in soil and the α-diversity of the soil fungal community. Additionally, P. chlororaphis inoculation decreased the abundance of detrimental P. penicillatus and mitigated the WMD incidence, which correspondingly increased the morel yield. Metagenomics revealed that increasing the pseudomonads in the M. importuna mycosphere altered the functionalities of the M. importuna soil microbiota, enhancing the abundances of genes encoding chitinase and alkaline protease and reducing the abundances of genes encoding glucanase and laccase. Under P. chlororaphis inoculation, pathways associated with pathogenic invasion were under-represented in the soil microbiota. These results enhance our understanding of bacterial–fungal interactions within soil ecosystems and demonstrate the potential for disease suppression through microbiota manipulation within the fungal mycosphere. These insights may lead to innovative approaches to combat fungal pathogens and enhance the health and productivity of valuable fungal crops such as morels.

The dissolution of fertilisers is the initial process that takes place in soils following fertiliser application and influences the fate and effectiveness of fertilisers. Currently, there are only a few methods for studying fertiliser dissolution in soil. These approaches typically do not accurately represent real soil-fertiliser systems and are susceptible to errors, since they are influenced by processes associated with the loss or retention of the trace ions of the fertiliser. Low field NMR or time-domain NMR (¹H-TDNMR) is typically employed for studying ¹H in fluids (or mobile ¹H), however, special pulse sequences enable the selective detection of ¹H in solids. Furthermore, it is possible to filter out undesired signals like ¹H from minerals and from soil organic matter. This allows for the detection and monitoring of ¹H only from protonated fertilisers (e.g., ammonia, (di)-hydrogen phosphates, etc.). The aim of this study is to present an efficient procedure which monitors the dissolution of fertilisers in soils using ¹H-TDNMR. For this, six contrasting New Zealand soils and four protonated fertilisers - NH₄Cl, NH₄NO₃, NaH₂PO₄.H₂O, and (NH₄)₂HPO₄ - were utilised. The proposed method efficiently, accurately, and precisely, monitored the dissolution of the studied fertilisers in all the tested soils under different rain regimes, from violent rain (60 mm h^− 1) to light rain (2 mm h^− 1) with a time interval (temporal resolution) as short as 5 s.

Despite the rapid development of microbial inoculants use, their effectiveness still lacks robustness, partly due to our limited understanding of the factors influencing their establishment in soil. Recurrent inoculation can temporarily increase their abundance, but the effect of this inoculation strategy on plant growth and on the resident microbial community is still poorly studied. Here, we investigated maize growth and soil bacterial community responses under recurrent inoculation of the plant-beneficial bacterium Pseudomonas fluorescens B177. We further assessed how the effect of recurrent inoculation was modulated by the inoculant dose, the application timing and the soil type. Recurrent inoculation at high dose transiently increased the abundance of P. fluorescens B177 and resulted in larger shifts in the resident bacterial community compared to a single inoculation event. Moreover, recurrent inoculation prior to sowing had the strongest effect on maize growth, with increased shoot dry weight by 47.4%, likely due to an indirect effect of the inoculant through early changes in the resident community. Altogether these findings highlight the significance of recurrent pre-sowing inoculations as an alternative strategy for promoting plant growth.