Response of bacterial community composition and co-occurrence network to straw and straw biochar incorporation

Probiotic-Enzyme Synergy Regulates Fermentation of Distiller's Grains by Modifying Microbiome Structures and Symbiotic Relationships

The high fiber content and low rumen digestibility prevent the efficient use of distiller's grains (DGS) in ruminant feeds. This study investigated the effects of probiotics (Lactiplantibacillus plantarum and Bacillus subtilis) and enzymes (β-glucanase, xylanase, β-mannanase, and cellulase) on DGS nutrient content, ruminal degradability, and microbial communities under anaerobic storage for 30 days. Groups included control (C), probiotics (B), enzymes (E), and their mixture (EB). As compared to groups C, B, and E, neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose, and cellulose contents were significantly decreased and the ruminal degradability of NDF and ADF at 48 h was significantly increased in group EB (p < 0.05). Enzyme activities significantly affected bacterial abundance, and the contents of these enzymes were negatively correlated with the content of fibrous components. The abundances of Bacillus and Rummeliibacillus were negatively correlated with fiber content but positively correlated with the activities of these enzymes. The symbiotic relationship between Bacillus and Anaerocolumna in the EB group sustained the synergistic effects of probiotics and enzymes. Co-fermentation of probiotics and enzyme additives enhanced the nutritional value of DGS, which was associated not only with probiotic-enzyme synergy but also variations in dominant microbes and microbiome commensal relationships.

Response of Soil Bacteria to Short-Term Nitrogen Addition in Nutrient-Poor Areas

Increasing nitrogen (N) addition induces soil nutrient imbalances and is recognized as a major regulator of soil microbial communities. However, how soil bacterial abundance, diversity, and community composition respond to exogenous N addition in nutrient-poor and generally N-limited regions remains understudied. In this study, we investigated the effects of short-term exogenous N additions on soil bacterial communities using quantitative polymerase chain reaction (PCR) and Illumina Miseq sequencing in an in situ N addition field experiment. The results showed that a low nitrogen addition increased the observed species (Sobs) of the bacterial community, and with the increased nitrogen addition, the Sobs of bacteria gradually decreased, especially the unique OTUs. The relative abundance of Proteobacteria, Actinobacteria, and Gemmatimonadetes increased with increasing nitrogen addition, whereas the relative abundance of Chloroflexi and Firmicutes decreased. Soil properties play an important role in bacterial community structure at phylum or genus levels. Short-term nitrogen addition increased the proportion of nodes from Actinobacteria and Proteobacteria in the co-occurrence network and enhanced the stability of the microbial network. Actinobacteria may play an important role in constructing the network. Our study aims to explore the effects of nitrogen addition on the diversity, composition, and structure of soil bacterial communities in nutrient-poor areas caused by ecological disturbances.

Food waste biochar for sustainable agricultural use: Effects on soil enzymes, microbial community, lettuce, and earthworms

This study investigates the effects of food waste biochar (FWB) on the biological properties of soil, including the microbial community structure, enzyme activities, lettuce growth, and earthworm ecotoxicity. This holistic assessment of various soil organisms was used to assess the potential of FWB as a soil amendment strategy. Pot experiments were carried out over a 28-d period using various FWB concentrations in soil (0-3% w/w). The presence of FWB enhanced the activity of alkaline phosphatase and beta-glucosidase in proportion to the FWB concentration. Similarly, the dehydrogenase activity after 28 d was positively correlated with the FWB concentration. Notably, the application of FWB improved the bacterial diversity in the soil, particularly among hydrocarbonoclastic bacteria, while also prompting a shift in the fungal community structure at the class level. Measures of lettuce growth, including total fresh weight, shoot length, and leaf number, also generally improved with the addition of FWB, particularly at higher concentrations. Importantly, FWB did not adversely affect the survival or weight of earthworms. Collectively, these findings suggest that FWB can enhance soil microbial enzyme activity and support plant growth-promoting rhizobacteria, potentially leading to increased crop yields. This highlights the potential of FWB as an eco-friendly soil amendment strategy.

Enhanced phytoremediation of cadmium-contaminated soil using chelating agents and plant growth regulators: effect and mechanism

The heavy metal cadmium (Cd) is a major threat to food safety and human health. Phytoremediation is the most widely used remediation technology, and how to improve the remediation efficiency of phytoremediation has become a key issue. In this study, we constructed an intensive phytoremediation technology for remediation of Cd-contaminated soil with biodegradable chelating agent and plant growth regulator combined with maize and investigated the mechanism of this technology. The results showed that the best remediation effect was achieved in the treatment with 10-6 mol l-1 gibberellic acid (GA3) and 6 mmol kg-1 aspartate diethoxysuccinic acid (AES) combined with maize. In this treatment, the total biomass and extraction efficiency of maize were 3.6 and 8.67 times higher than those of the control, respectively, and the antioxidant enzyme activities of maize were also increased. The soil was enriched with dominant bacterial genera that promote plant growth and metabolism and tolerance to heavy metal stress, which in turn promoted maize growth and Cd accumulation. Structural equation modelling results indicated a large effect of plant Cd concentration and plant antioxidant enzyme activity on plant Cd extraction. The enhanced phytoremediation technology showed good potential for safe use of Cd-contaminated soil.

Core bacteria and fungi in response to residue retention and their contribution to soil multifunctionality in maize agroecosystem

Core microbiome has been proven to play crucial roles in soil function. However, we still lack knowledge on how core microbiome responds to crop residue retention, and whether they contribute to this process. Consequently, we examined the effect of residue retention on soil core and non-core microbial communities in maize seedling, mature stage and freezing period based on a multi-site field experiment in Sanjiang Plain, Northeast China. Totally, 247 bacterial amplicon sequence variants (ASVs) and 109 fungal ASVs were identified as core microbiota. Both core and non-core bacterial/fungal community composition were significantly influenced by residue retention across all study sites. Especially, the core fungal community shifted towards a saprotroph-dominated community. Normalized stochastic ratio pattern revealed that that deterministic process dominated both core and non-core microbial community assembly processes. Residue retention enhanced the deterministic process of core microbial community assembly, while exhibited opposite effect on non-core microbial community. This study also revealed that soil fungi were more sensitive to residue retention than bacteria, with a larger proportion of core fungi were enriched or depleted by residue retention. In addition, residue retention complicated core bacterial co-occurrence network, while simplified fungal network. Our results pointed out both no reduction in microbial diversity or collapse in microbial network structure after repeated freezing-thawing cycles. The potential function of core microbiome was evaluated through random forest analysis and structural equation model, the results indicated core microbiome contributed more to multifunctionality than non-core microbiome. Overall, this study strengthened our understanding of soil core microbiome in response to residue retention, and highlighted their importance in maintaining soil multifunctionality.

Straw Soil Conditioner Modulates Key Soil Microbes and Nutrient Dynamics across Different Maize Developmental Stages

Soil amendments may enhance crop yield and quality by increasing soil nutrient levels and improving nutrient absorption efficiency, potentially through beneficial microbial interactions. In this work, the effects of amending soil with straw-based carbon substrate (SCS), a novel biochar material, on soil nutrients, soil microbial communities, and maize yield were compared with those of soil amendment with conventional straw. The diversity and abundance of soil bacterial and fungal communities were significantly influenced by both the maize growth period and the treatment used. Regression analysis of microbial community variation indicated that Rhizobiales, Saccharimonadales, and Eurotiales were the bacterial and fungal taxa that exhibited a positive response to SCS amendment during the growth stages of maize. Members of these taxa break down organic matter to release nutrients that promote plant growth and yield. In the seedling and vegetative stages of maize growth, the abundance of Rhizobiales is positively correlated with the total nitrogen (TN) content in the soil. During the tasseling and physiological maturity stages of corn, the abundance of Saccharimonadales and Eurotiales is positively correlated with the content of total carbon (TC), total phosphorus (TP), and available phosphorus (AP) in the soil. The results suggest that specific beneficial microorganisms are recruited at different stages of maize growth to supply the nutrients required at each stage. This targeted recruitment strategy optimizes the availability of nutrients to plants and ultimately leads to higher yields. The identification of these key beneficial microorganisms may provide a theoretical basis for the targeted improvement of crop yield and soil quality. This study demonstrates that SCS amendment enhances soil nutrient content and crop yield compared with conventional straw incorporation and sheds light on the response of soil microorganisms to SCS amendment, providing valuable insights for the future implementation of this material.

The soft rock can promote the improvement of aeolian sandy soil in Mu Us Sandy Land, China

This study focuses on the significance of improving the land degradation of Mu Us Sandy Land to increase cultivated land area and promote ecological green development. The research objects were four kinds of mixed soils, and rhizosphere soils were collected during the crop harvesting period. The volume ratio of soft rock to sand was 0:1 (control check, CK), 1:5 (composite soil one, PS1), 1:2 (composite soil two, PS2), and 1:1 (composite soil three, PS3). The results showed that the large aggregates were primarily mechanically stable aggregates, while the small aggregates were mainly water-stable aggregates. The soft rock promoted the increase of clay and silt content in sandy soil, and the soil texture changed from sand to loam. The contents of organic matter, available phosphorus, and available potassium increased significantly under PS2 and PS3 treatments, but there was no significant difference between them. Total nitrogen had no significant difference among treatments. Actinobaciota, Proteobateria, and Chloroflexi were the dominant bacteria in rhizosphere soil, accounting for about 75% of all microorganisms. At the Genus level, the soft rock contributes to richer species composition. The diversity index, evenness index, and richness index was higher in PS1, and the available phosphorus and available potassium content promoted the increase of diversity. Therefore, when the proportion of soft rock and sand compound soil is between 1: 5 and 1: 2, it can be used as an important basis and technical parameter for Mu Us Sandy Land improvement.