Alter Soil Microbial Community Research Articles

Increased soil bacteria-fungus interactions promote soil nutrient availability, plant growth, and coexistence

Tree species and interkingdom relationships in the belowground metacommunity are key factors in determining soil microbial diversity and community composition. However, how bacterial-fungal interactions mediate soil nutrient and plant growth remains largely unexplored in the coniferous forests. Here, we selected three types of naturally growing coniferous forests on the Loess Plateau—pure stands of Platycladus orientalis, mixed stands of Platycladus orientalis and Pinus tabuliformis, and pure stands of Pinus tabuliformis—to compare the differences in soil properties, microbial diversity and community composition, soil enzymatic activity, and plant growth conditions across these stand types. We found that tree species mixing significantly alters soil microbial community diversity and composition, increasing the positive associations between bacteria and fungi. Compared to pure stands, mixed stands exhibit significantly higher bacterial diversity, whereas fungal diversity shows no significant difference. Additionally, available soil nutrients (ammonium nitrogen and available phosphorus) are significantly increased in mixed stands, along with their associated soil enzymatic activities. The partial least squares path model suggests that higher bacterial diversity enhances bacterial-fungal positive interactions, increasing the relative abundance of ectomycorrhizal fungi and the decomposition rate of organic matter in mixed stands, thereby boosting soil nutrient availability and plant growth. These results highlight the importance of positive bacterial-fungal associations for soil nutrient availability and plant growth, deepen the understanding of the role of soil microbial interactions in mediating plant species coexistence. Most importantly, our results implied a stable coexistence of the pioneer P. orientalis and the late successional species P. tabuliformis in the Loess Plateau region and provided a microbiological interpretation.

Nitrogen induced soil carbon gains are resistant to loss after the cessation of excess nitrogen inputs

Nitrogen (N) deposition has increased soil carbon (C) storage across eastern US temperate forests by reducing microbial decomposition. However, the fate of these N-induced soil C gains are uncertain given strong declines in N-deposition rates and rising soil temperatures. As N deposition has reduced soil pH and plant C investments into the rhizosphere, we compared the extent to which removing limitations to microbial decomposition by increasing soil pH, adding artificial root exudates, or elevating soil temperature would increase microbial decomposition in soils that have and have not received excess N inputs. We hypothesized that alleviating these microbial decomposition limitations would prime soil C losses from soils that have received excess N inputs. To test this hypothesis, we conducted a soil microcosm experiment where we compared microbial respiration, microbial biomass, and soil enzyme activity in soils from an unfertilized watershed and a previously N-fertilized watershed 4 years after the end of a 30-year N deposition experiment at the Fernow Experimental Forest in West Virginia. In both watersheds, we found that removing pH, plant carbon, or temperature limitations to decomposition stimulated microbial respiration. However, microbial decomposition and soil C losses were consistently lower in the previously N-fertilized watershed across all treatments. This response, coupled with a lack of differences in microbial biomass between watersheds and treatments, suggests that long-term N fertilization has fundamentally altered soil microbial communities and has led to a sustained impairment of the ability of the microbial community to decompose soil organic matter. Collectively, our results indicate that the legacy effect of N deposition on microbial communities may influence the persistence of soil C stocks in the face of global change.

Prescribed burning alters soil microbial community structure by changing soil physicochemical properties in temperate forests of northern China

Prescribed burning is commonly used to maintain forest ecosystem functions and reduce the risk of future wildfires. Although many studies have investigated the response of microbial community to wildfires in forest ecosystems, the effects of prescribed burnings on soil microbial community structure are less studied. It is also unclear that how post-fire soil physiochemical properties changes affected soil microbial communities. Here, we studied the impacts of prescribed burning on soil microbiome in three typical temperate forests of northern China by collecting soil physicochemical and high-throughput sequencing for 16S rRNA and 18S rRNA was applied to analyze the diversity and community composition of soil microbes (bacteria and fungi). Compared with pre-fire condition, prescribed burning significantly decreased Chao1 index and altered soil bacterial communities (P < 0.05), whereas it had no significant effect on fungal diversity and community structure of the (P > 0.05). Planctomycetes and Actinobacteria made the greatest contributions to the bacterial community dissimilarity between the pre-fire and post-fire conditions. The main variables influencing the post-fire soil microbial community structure are soil pH, available phosphorus, total nitrogen, and the ratio of soil total carbon to soil total nitrogen, which could account for 73.5% of the variation in the microbial community structure in these stands. Our findings demonstrated a great discrepancy in the responses of bacteria and fungi to prescribed burning. Prescribed burning altered the soil microbial structure by modifying the physicochemical properties. Our results pointed that it is essential to evaluate the impact of prescribed burnings on forest ecosystem functions. These findings provide an important baseline for assessing post-fire microbial recovery in the region and offer critical guidance for restoration efforts.

Hydroxyapatite self-doped biochar with MgO modification immobilizes heavy metal and alters soil microbial community

Functionalized biochars are highly effective in the remediation of heavy metals and the improvement of soil properties. In this study, we prepared a hydroxyapatite self-doped biochar (FB) using fish scales as raw material, and impreged FB with MgCl2 following by pyrolysis to obtain MgO-loaded FB (MFB). A soil incubation experiment was conducted to explore the influence of MFB on the immobilization of Cu, Cd, and Pb, alongside the impact on the soil properties and bacterial community. The results demonstrated that the nano-hydroxyapatite components and MgO micro-nanoparticles on MFB promoted the immobilization of heavy metals in soils through dissolution-precipitation and ion-exchange. The availability of Cu, Cd, and Pb in soils amended with MFB was significantly decreased by 69.1 %, 63.5 %, and 53.7 %, respectively, compared to CK. Furthermore, the MFB amendment significantly increased soil organic carbon and available P, as well as enhanced enzyme activities related to the C-, N-, and P-cycles. Notably, the MgO loaded on biochar played a crucial role in altering the diversity and composition of soil bacterial communities. The complexity and stability of the co-occurrence networks of bacterial communities increased following MgO-loaded biochar addition, and there were more frequent positive interactions among bacterial taxa within the network. The effects of MFB on immobilizing heavy metals and shaping bacterial communities were conducive to the restoration of soil ecological functions. These findings provide a promising strategy for the remediation of heavy metal contaminated soils.

Plant growth-promoting microorganisms drive K strategists through deterministic processes to alleviate biological stress caused by Fusarium oxysporum

Soybean root rot, caused by soil-borne pathogens such as Fusarium oxysporum, frequently occurs in Northeast China and leads to a decline in soil health and becoming a bottleneck for soybean yield in the region. To address this issue, applying beneficial microorganisms and altering soil microbial community structure have become effective strategies. In this study, the 90-day soybean pot experiment was conducted to explore the assembly process and life strategy selection of bacterial communities in the rhizosphere of healthy (inoculated with Funneliformis mosseae, F group and treated with Pseudomonas putida, P group) and diseased (inoculated with F. oxysporum, O group) soybean plants, as well as the recovery effect of beneficial microorganisms on soil-borne diseases (combined treatments OP and OF). Results indicated that in healthy soils (P and F), microbial community assembly process in the soybean rhizosphere was entirely governed by heterogeneous selection (HeS, 100 %). However, inoculated with P. putida (OP) was primarily driven by stochastic processes (HeS 40 %, dispersal limitation (DL) 60 %), and the F. mosseae treatment (OF) predominantly followed a deterministic process (HeS 89 %, DL 11 %) in diseased soils. Inoculation of plant growth-promoting microorganisms (PGPMs) in diseased soil drove the life strategy of the rhizosphere bacterial community from r- to K-strategy, evident from the lower rRNA operon (rrn) copy numbers (O 3.7, OP 2.1, OF 2.3), higher G+ to G- ratios (O 0.47, OP 0.58, OF 0.57), and a higher abundance of oligotrophs (O 50 %, OP 53 %, OF 54 %). In healthy (P and F) and diseased (O, OP, OF) rhizosphere soils, OTU820, OTU6142, and OTU8841 under the K-strategy, and OTU6032 and OTU6917 under the r-strategy, which served as keystone species, had a significant promoting relationship with plant biomass and defense capabilities ( p ＜0.05). Additionally, inoculation of PGPMs improved autotoxin degradation and positively correlated with bacterial life strategies in both healthy and diseased soils (P, F, OP and OF) ( p ＜0.05). These findings enhance our understanding of soil-microbe interactions and offer new insights and precise control measures for soybean disease management and soil environment remediation.

The Response of Rhizosphere Microbial C and N-Cycling Gene Abundance of Sand-Fixing Shrub to Stand Age Following Desert Restoration.

Rhizosphere microorganisms play a pivotal role in biogeochemical cycles, particularly in relation to carbon (C) and nitrogen (N) cycles. However, the impact of stand age on the composition of rhizosphere microbial communities and the abundance involved in C and N cycling remains largely unexplored in restoration ecosystems dominated by shrubs of temperate deserts. This study focuses on revealing changes in microbial composition and functional genes in the rhizosphere soil of Caragana korshinskii after revegetation, as well as their response mechanisms to changes in environmental factors. The alpha diversity of bacteria tended to increase with stand age, whereas that of fungi decreased. The abundance of denitrification; dissimilatory nitrate reduction to ammonium, nitrification, and ammonium assimilation; and C fixation-related gene levels increased with stand age, whereas those related to the degradation of starch, pectin, hemicellulose, cellulose, and aromatics decreased. The parameters MBC, MBN, and TC were the key factors affecting the bacterial community, whereas the fungal community was regulated by TN, EC, pH, and MBC. Stand age indirectly regulated C and N cycling functions of genes through altered soil properties and microbial community structures. This study presents a novel approach to accurately evaluate the C and N cycling dynamics within ecosystems at various stages of restoration.

Winter cover crops and irrigation alter soil microbial community composition in an arid cropping system

Cover cropping is a well-established strategy to improve soil health, especially in arid and semi-arid agricultural systems. Benefits to soil health are often mediated via effects of cover crops on soil microbial community structure, function and diversity, crucial for regulating soil biogeochemical cycles, eventually promoting agricultural sustainability. However, limited water availability is a major constraint for both cover crop growth and soil microbial activity. This study sought to characterize and elucidate the shifts in soil microbial community structure in response to different cover crops and differential irrigation treatments using phospholipid fatty acid (PLFA) profiling in southern New Mexico. We tested five cover crop treatments: Pisum sativum (Australian winter pea), Hordeum vulgare cv. Stockford (barley), Brassica juncea cv. Caliente 199 (brown mustard), a three-way mix, and a fallow control — in combination with irrigation treatments of one, two, or three irrigation applications — in a split-plot design over two years. Zea mays (sweet corn) was grown as the summer cash crop. We collected soil samples just after cover crop planting in the fall of 2018, following second year cover crop termination but during Z. mays growth in June 2020, and after the second season of Z. mays growth in October 2020. Differential irrigation treatments did not lead to consistent patterns of change under any cover crop or irrigation treatment. However, PLFA parameters in cover cropped compared to winter fallow plots tended to decrease under one and three irrigations but increased with two irrigations. Changes were more common for bacterial than for fungal PLFA biomarkers, and more common in B. juncea and H. vulgare cover crops than in P. sativa or the mix. It is important to note that, while cover crop effects were inconsistent, cover cropping did lead to some shifts in PLFA biomarkers, even in the short two-year period of cover cropping.

Effects of several long-term soil health treatments on populations of Pratylenchus penetrans and the soil microbial community

Soil suppressiveness can reduce the damage by plant parasitic nematodes (PPN) in agricultural soils and is conveyed by the activity of soil microorganisms. While natural suppressiveness has been reported, it is still poorly understood if soil suppressiveness can be elicited by manipulating the soil microbial community. In the present study we assessed the number of the Pratylenchus penetrans (Pp) and the bacterial and fungal community composition over 7 years in a long-term soil health experiment. The field experiment consisted of an organic and conventional agricultural land management system and three soil health treatments (SHT): an untreated control (CT), anaerobic disinfestation (AD) and a combination of marigold cover cropping, compost and chitin amendment (CB). The land management systems were kept continuously, while the soil health treatments were applied only twice in seven years. The microbial community significantly differed between the organic and conventional system, but there was no significant difference in Pp numbers between the two systems. However, both the CB treatment and to a lesser extent the AD treatment reduced Pp numbers and increased yield with the effect being the strongest in the years immediately after the treatment. Accordingly, both the bacterial and fungal community differed significantly between the treatments, the differences being largest in the years after the treatments. Notably, the CB treatment elicited both long-term changes in the microbial community and a reduction of Pp numbers lasting for at least three years. These results indicated that a combination of treatments can lead to an altered soil microbial community in combination with persisting suppressiveness of Pp.

Long-term warming in a temperate forest accelerates soil organic matter decomposition despite increased plant-derived inputs

Climate change may alter soil microbial communities and soil organic matter (SOM) composition. Soil carbon (C) cycling takes place over multiple time scales; therefore, long-term studies are essential to better understand the factors influencing C storage and help predict responses to climate change. To investigate this further, soils that were heated by 5 °C above ambient soil temperatures for 18 years were collected from the Barre Woods Soil Warming Study at the Harvard Forest Long-term Ecological Research site. This site consists of large 30 × 30 m plots (control or heated) where entire root systems are exposed to sustained warming conditions. Measurements included soil C and nitrogen concentrations, microbial biomass, and SOM chemistry using gas chromatography–mass spectrometry and solid-state 13C nuclear magnetic resonance spectroscopy. These complementary techniques provide a holistic overview of all SOM components and a comprehensive understanding of SOM composition at the molecular-level. Our results showed that soil C concentrations were not significantly altered with warming; however, various molecular-level alterations to SOM chemistry were observed. We found evidence for both enhanced SOM decomposition and increased above-ground plant inputs with long-term warming. We also noted shifts in microbial community composition while microbial biomass remained largely unchanged. These findings suggest that prolonged warming induced increased availability of preferred substrates, leading to shifts in the microbial community and SOM biogeochemistry. The observed increase in gram-positive bacteria indicated changes in substrate availability as gram-positive bacteria are often associated with the decomposition of complex organic matter, while gram-negative bacteria preferentially break down simpler organic compounds altering SOM composition over time. Our results also highlight that additional plant inputs do not effectively offset chronic warming-induced SOM decomposition in temperate forests.

Soil health influenced more by conservation tillage and cropping practice than irrigation level in a sandy semiarid cotton system

AbstractCropping systems in semiarid regions have frequently relied on continuous tillage and irrigation, but declining groundwater resources have prompted a greater focus on conservation practices to improve soil health and water storage. We compared soil health responses from cotton production systems in semiarid, coarse‐textured soils with different crop management strategies under high or low irrigation levels. Management systems included continuous cotton with conventional tillage (CCCT) compared to no‐till cotton with a rye cover crop (NTCR) and no‐till cotton with a wheat‐fallow rotation (NTCW), including high or low irrigation zones within each system. Samples were collected annually from two bulk soil depths (0–10 cm and 10–20 cm) and root‐associated soils 7 years after systems were established and continued for 2 years. We found that cropping system, but not irrigation level, altered soil microbial communities and other soil health indicators. Despite variation between study years and sampling zones, the conservation systems had greater soil microbial community size via ester‐linked fatty acid methyl ester (EL‐FAME or FAME) analysis, extracellular enzyme activities, and soil organic matter than the CCCT system. The NTCW system also had greater arbuscular mycorrhizal fungi FAME abundance. Our study suggests that no‐till and conservation strategies such as cover cropping and rotation can improve biological soil health indicators in these sandy semiarid soils even with limited irrigation.

Exotic plants introduction changed soil nutrient cycle and symbiotic relationship with arbuscular mycorrhizal fungi in wetland ecological projects.

In the process of applying exotic plants to wetland ecological restoration, insufficiently evaluated alien species may exhibit strong competitiveness and fecundity. Once introduced, they can displace native flora, disrupt the original ecological balance, diminish biodiversity, and even induce ecosystem dysfunction. Furthermore, exotic plants have the potential to alter soil microbial community structure, including the composition and activity of beneficial symbiotic microorganisms such as arbuscular mycorrhizal fungi (AMF), thereby impacting soil nutrient cycling and interplant nutrient competition. Here, we conducted three consecutive years of sampling experiments to investigate the succession of AMF communities associated with the invasive plant Spartina alterniflora along an initial introduction chronosequence, and to identify the key environmental factors influencing its response to S. alterniflora invasion. Our findings reveal that early-stage invasion by S. alterniflora alters the composition of soil AMF communities with unclassified_c__Glomeromycetes and Glomus-viscosum-VTX00063 consistently dominating. Additionally, as the duration of introduction increases, the diversity of rhizosphere soil AMF significantly decreases, while its evenness remains relatively stable. It's indicated that soil ω, AN, AK and N/P ratio were the main influencing factors of the integral AMF community. Notably, soil available phosphorus (AP) emerges as a positive influence on the important AMF taxa. The results confirm the mutual feedback effect between the invasion of the perennial herb S. alterniflora and AMF, in which specific AMF assist in nutrient absorption to promote S. alterniflora growth, potentially facilitating its rapid and successful invasion of new habitats. Given the likely differential effects of AMF communities on various plant species, our findings could contribute to anticipating future AMF-mediated effects during the introduction of alien plants.

Recover of Soil Microbial Community Functions in Beech and Turkey Oak Forests After Coppicing Interventions

Forest management influences the occurrence of tree species, the organic matter input to the soil decomposer system, and hence, it can alter soil microbial community and key ecosystem functions it performs. In this study, we compared the potential effect of different forest management, coppice and high forest, on soil microbial functional diversity, enzyme activities and chemical-physical soil properties in two forests, turkey oak and beech, during summer and autumn. We hypothesized that coppicing influences soil microbial functional diversity with an overall decrease. Contrary to our hypothesis, in summer, the functional diversity of soil microbial community was higher in both coppice forests, suggesting a resilience response of the microbial communities in the soil after tree cutting, which occurred 15–20 years ago. In beech forest under coppice management, a higher content of soil organic matter (but also of soil recalcitrant and stable organic carbon) compared to high forest can explain the higher soil microbial functional diversity and metabolic activity. In turkey oak forest, although differences in functional diversity of soil microbial community between management were observed, for the other investigated parameters, the differences were mainly linked to seasonality. The findings highlight that the soil organic matter preservation depends on the type of forest, but the soil microbial community was able to recover after about 15 years from coppice intervention in both forest ecosystems. Thus, the type of management implemented in these forest ecosystems, not negatively affecting soil organic matter pool, preserving microbial community and potentially soil ecological functions, is sustainable in a scenario of climate change.

Interruption after Short-Term Nitrogen Additions Improves Ecological Stability of Larix olgensis Forest Soil by Affecting Bacterial Communities.

Atmospheric nitrogen deposition can alter soil microbial communities and further impact the structure and function of forest ecosystems. However, most studies are focused on positive or negative effects after nitrogen addition, and few studies pay attention to its interruption. In order to investigate whether interruption after different levels of short-term N additions still benefit soil health, we conducted a 2-year interruption after a 4-year short-term nitrogen addition (10 and 20 kg N·hm-2·yr-1) experiment; then, we compared soil microbial diversity and structure and analyzed soil physicochemical properties and their correlations before and after the interruption in Larix olgensis forest soil in northeast China. The results showed that soil ecological stabilization of Larix olgensis forest further improved after the interruption compared to pre-interruption. The TN, C:P, N:P, and C:N:P ratios increased significantly regardless of the previous nitrogen addition concentration, and soil nutrient cycling was further promoted. The relative abundance of the original beneficial microbial taxa Gemmatimonas, Sphingomonas, and Pseudolabrys increased; new beneficial bacteria Ellin6067, Massilia, Solirubrobacter, and Bradyrhizobium appeared, and the species of beneficial soil microorganisms were further improved. The results of this study elucidated the dynamics of the bacterial community before and after the interruption of short-term nitrogen addition and could provide data support and a reference basis for forest ecosystem restoration strategies and management under the background of global nitrogen deposition.

Biochar as a green solution to drive the soil carbon pump

Biochar is a nature-based green solution to lift soil carbon storage and mitigate carbon release. Here, we propose a novel concept of biochar carbon pump (BCP) that bridges microbial carbon pump (MCP) and mineral carbon pump (MnCP), facilitating effective carbon sequestration. The BCP functions to promote carbon storage by introducing biochar-derived persistent C into soil, enhancing negative priming effects, altering soil microbial communities, and reinforcing organo-organic and organo-mineral interactions. Recognizing the value of BCP in bridging MCP and MnCP to facilitate diverse natural reactions for soil carbon sequestration is particularly significant in addressing climate change.

Adaptive multi-paddock grazing increases mineral associated soil carbon in Northern grasslands

Grassland soils play an important role in sequestering carbon (C) and are primarily used for livestock grazing. Grazing management can increase the amount of C stored in soils and the distribution of C in different soil fractions by altering soil microbial community structure, thereby influencing the persistence of soil C over time. Adaptive multi-paddock grazing (AMP), grazing cattle at high stock densities with long periods between grazing events, is considered to enhance grassland sustainability, productivity, and soil C compared to more conventional grazing practices (continuous to slow rotational). However, whether and how AMP grazing might affect the amount of C stored in different soil fractions has received little attention. Soil samples (0–15 cm depth) were collected from 24 ranches in a paired design, where 12 ranches practiced AMP grazing and 12 neighboring ranches practiced conventional grazing. Soil organic C (SOC) and total nitrogen were measured in different soil particle size [fine (<53 µm), medium (53–250 µm) and coarse (>250 µm)], and density [light (>1.6 g cm−3), and heavy (<1.6 g cm−3)] fractions. Soil bacterial and fungal biomass and abundances were obtained from phospholipid fatty acid analysis. Mean weights of soil microaggregates and heavy fractions were higher in soil exposed to AMP grazing, whereas mean weights of macroaggregates and light fractions were higher in conventionally grazed soils. In warmer and drier climatic conditions, SOC in both bulk soils and within various size and density fractions tended to decrease. Soil organic C (both concentration and stock) were significantly higher in the fine soil fractions under AMP management than conventionally grazed grasslands. Given that SOC in fine fractions, is more mineral associated and recalcitrant, our results indicate that AMP grazing increased the size of the stable SOC pool. The increased carbon pool in the fine fraction was associated with greater fungal to bacterial ratios, suggesting a possible biological mechanism for the increase. Overall, the results indicate that AMP grazing may be beneficial for sequestering more stable carbon that helps mitigate the effects of climate change.

Effect of n-hexadecanoic acid on N2O emissions from vegetable soil and its synergism with Pseudomonas stutzeri NRCB010

Recently, it has been recommended to utilize specific plant root metabolites to decrease nitrous oxide (N2O) emissions from agricultural soil. However, only a limited number of plant root metabolites have been shown to decrease soil N2O emissions, and their combined effects with plant growth-promoting rhizobacteria, as well as the mechanisms involved in mitigating N2O emissions, remain to be explored. This study investigated the impact and microbial mechanisms of three tomato root exudate metabolites, namely, methyl hexadecanoate, methyl stearate, and n-hexadecanoic acid, on N2O emissions. In a pure culture experiment, n-hexadecanoic acid significantly enhanced Pseudomonas stutzeri NRCB010 auxin production, nitrogen removal, N2O reduction capacity, and N2O reductase activity. Methyl stearate significantly promoted NRCB010 N removal and the N2O reduction capacity. In soil microcosm and greenhouse pot experiments, n-hexadecanoic acid decreased N2O cumulative emissions by 34.3 % and 46.6 %, respectively, and further decreases were observed when combined with NRCB010. Additionally, n-hexadecanoic acid, both independently and in combination with NRCB010, significantly promoted tomato growth. N-hexadecanoic acid, alone or with NRCB010, also altered soil microbial communities and nitrogen-cycle functional gene abundance. Structural equation models revealed that n-hexadecanoic acid, either alone or with NRCB010, decreased N2O cumulative emissions by modifying the environmental conditions to be more conducive to N2O mitigation (e.g., higher soil pH and organic matter content), inhibiting N2O production (through a decrease in ammonia-oxidizing bacteria and nirK gene copy numbers), and promoting N2O reduction (by increasing nosZII gene copy numbers). Our results support the potential use of n-hexadecanoic acid in enhancing crop productivity and mitigating N2O emissions in agricultural soils.

Continuous cropping system altered soil microbial communities and nutrient cycles.

Understanding the response of microbial communities and their potential functions is essential for sustainability of agroecosystems under long-term continuous cropping. However, limited research has focused on investigating the interaction between soil physicochemical factors and microbial community dynamics in agroecosystems under long-term continuous cropping. This study probed into the physicochemical properties, metabolites, and microbial diversity of tobacco rhizosphere soils cropped continuously for 0, 5, and 20 years. The relative abundance of bacterial genera associated with nutrient cycling (e.g., Sphingomonas) increased while potential plant pathogenic fungi and beneficial microorganisms showed synergistic increases with the duration of continuous cropping. Variations in soil pH, alkeline nitrogen (AN) content, and soil organic carbon (SOC) content drove the shifts in soil microbial composition. Metabolites such as palmitic acid, 3-hydroxypropionic acid, stearic acid, and hippuric acid may play a key role in soil acidification. Those results enhance our ability to predict shifts in soil microbial community structure associated with anthropogenic continuous cropping, which can have long-term implications for crop production.

44-Years of Fertilization Altered Soil Microbial Community Structure by Changing Soil Physical, Chemical Properties and Enzyme Activity

44-Years of Fertilization Altered Soil Microbial Community Structure by Changing Soil Physical, Chemical Properties and Enzyme Activity

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

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. 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). 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. 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.

Soil C:N impacts on soil biological health and consequences on weed control in soybean and corn systems

Abstract Nitrogen availability has an important influence on agricultural weed growth, because many weeds in annual cropping systems are more competitive in high-nitrogen soils. A potential method to control nitrogen availability is through soil carbon amendments, which stimulate soil microbial growth and immobilize nitrogen. Additionally, carbon amendments may alter soil microbial community composition, increase soil biological functioning, and improve soil health. In a 2-yr field experiment in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.], we implemented five amendment treatments to test their ability to alter weed and crop growth through soil nitrogen availability and soil biological functioning. The treatments included: an untreated control, an unamended weed-free control, rye hay adding 3,560 kg C ha−1 and 3,350 kg C ha−1 in 2020 and 2021, respectively, sawdust adding 5,030 kg C ha−1 and 4,350 kg C ha−1 in 2020 and 2021, respectively, and a rye hay and sawdust combined treatment adding 8,590 kg C ha−1 and 7,700 kg C ha−1 in 2020 and 2021, respectively. Each treatment was replicated five times in corn and six times in soybean. Each season, we explored correlations between crop and weed biomass and weed community composition and nitrogen immobilization measured through soil respiration and nitrogen availability. We also explored changes to the soil microbial community composition and soil health as a secondary result of the carbon amendment treatments. Nitrogen availability was lowest in plots treated with the highest C:N amendment. Increasing carbon improved soil health metrics, but the microbial community composition was most affected by the rye hay treatment. Amendments with high C:N reduced weed growth in both soybean and corn plots but only selected for specific weed communities in soybean, leading to improved soybean competitiveness against weeds. In corn, crop growth and weed community composition remained consistent across amendment treatments. Targeted nitrogen immobilization may improve leguminous crop competition in some weed communities as part of an integrated weed management program.