Effects of straw return on bacterial communities in a wheat-maize rotation system in the North China Plain

Influences of tobacco straw return with lime on microbial community structure of tobacco-planting soil and tobacco leaf quality

Soil amendment is an important strategy for improving soil quality and crop yield. From 2014 to 2019, we conducted a study to investigate the effects of tobacco straw return with lime on soil nutrients, soil microbial community structure, tobacco leaf yield, and quality in southern Anhui, China. A field experiment was conducted with four treatments: straw removed (CK), straw return (St), straw return with dolomite (St + D), and straw return with lime (St + L). Results showed that after 5 years of application, the St + L significantly increased the soil pH by 16.9%, and the contents of soil alkaline nitrogen (N) and available potassium (K) by 17.2% and 23.0%, respectively, compared with the CK. Moreover, the St + L significantly increased tobacco leaf yield (24.0%) and the appearance (9.1%) and sensory (5.9%) quality of flue-cured tobacco leaves. The addition of soil conditioners (straw, dolomite, and lime) increased both the total reads and effective sequences of soil microorganisms. Bacterial diversity was more sensitive to changes in the external environment compared to soil fungi. The application of soil amendments (lime and straw) promoted the growth of beneficial microorganisms in the soil. Additionally, bacterial species had greater competition and limited availability of resources for survival compared to fungi. The results showed that soil microorganisms were significantly influenced by the presence of AK, AN, and pH contents. These findings can provide an effective method for improving the quality of flue-cured tobacco leaves and guiding the amelioration of acidic soil in regions where tobacco-rice rotation is practiced.

Biogas Slurry Significantly Improved Degraded Farmland Soil Quality and Promoted Capsicum spp. Production

This study reports on the effects of pretreated biogas slurry on degraded farm soil properties, microflora and the production of Capsicum spp. The responses of soil properties, microorganisms and Capsicum spp. production to biogas slurry pretreated soil were determined. The biogas slurry pretreatment of degraded soil increases the total nitrogen (0.15-0.32 g/kg), total phosphorus (0.13-0.75 g/kg), available phosphorus (102.62-190.68 mg/kg), available potassium (78.94-140.31 mg/kg), organic carbon content (0.67-3.32 g/kg) and pH value of the soil, while the population, diversity and distribution of soil bacteria and fungi were significantly affected. Interestingly, soil ammonium nitrogen, soil pH and soil nitrate nitrogen were highly correlated with the population of bacteria and fungi present in the pretreated soil. The soil with biogas slurry pretreatment of 495 m3/hm2 favored the seedling survival rate, flowering rate and fruit-bearing rate of Capsicum spp. and significantly reduced the rate of rigid seedlings. In this study, the application of 495 m3/hm2 biogas slurry to pretreat degraded soil has achieved the multiple goals of biogas slurry valorization, soil biofertilization and preventing and controlling plant diseases caused by soil-borne pathogenic microorganisms. These findings are of significant importance for the safe and environmentally friendly application of biogas slurry for soil pretreatment.

Synthesis and application of a compound microbial inoculant for effective soil remediation

Currently, there is a noticeable scarcity of applications that harness composite microbial inoculants to stimulate straw decomposition, nitrogen fixation, and crop growth. This study addresses this gap by selecting and coculturing three bacterial strains to create a composite microbial inoculant named HY-1. This innovative inoculant exhibits multifunctional capabilities, including nitrogen fixation, straw decomposition, and crop growth promotion. Furthermore, we aimed to explore its impact on soil microbial communities. The results showed that the optimal preparation conditions for the compound microbial inoculant HY-1 were 28.5 ± 0.6 °C, pH = 7.34 ± 0.40, and bacteriophage ratio 1:2:1 (Microbacterium: Streptomyces fasciatus: Bacillus amyloliquefaciens). Compared to single strains, the combination exhibited higher levels of cellulose-degrading and nitrogen-fixing enzyme activity, increased the straw degradation rate by 37.91% within 180 days, and significantly promoted the growth of corn seedlings. Under the condition of straw return, the compound bio-fungicide HY-1 effectively improved the soil microbial diversity. At that time, the soil had the highest number of unique bacterial operational taxonomic units (166), and the abundance of Proteobacteria in the soil increased by 7.24%, while that of Acidobacteriota decreased by 2.27%. The biosynthetic function of the cell wall/membrane/periplasm and the metabolic function of transporting inorganic ions were significantly enhanced. In this study, we discovered that employing coculturing techniques to produce the composite microbial inoculant HY-1 and applying it in the field effectively compensates for the limitations of single-strain inoculants, which often exhibit fewer functions and less pronounced effects. This approach demonstrates significant potential for enhancing the quality of agricultural soils.

Developments and Prospects of Farmland Application of Biogas Slurry in China-A Review

Biogas slurry (BS) is an attractive agricultural waste resource which can be used to regulate soil microbial communities, enhance nutrient absorption capacity of crops, promote plant-soil interactions, and consequently, increase crop productivity. Presently, BS discharge is not environmentally friendly. It is therefore necessary to explore alternative efficient utilization of BS. The use of BS as fertilizer meets the requirements for sustainable and eco-friendly development in agriculture, but this has not been fully actualized. Hence, this paper reviewed the advantages of using BS in farmland as soil fertilization for the improvement of crop production and quality. This review also highlighted the potential of BS for the prevention and control of soil acidification, salinization, as well as improve microbial structure and soil enzyme activity. Moreover, this review reports on the current techniques, application methods, relevant engineering measures, environmental benefits, challenges, and prospects associated with BS utilization. Lastly, additional research efforts require for optimal utilization of BS in farmlands were elucidated.

Effects of Maize-Crop Rotation on Soil Physicochemical Properties, Enzyme Activities, Microbial Biomass and Microbial Community Structure in Southwest China

Introducing cover crops into maize rotation systems is widely practiced to increase crop productivity and achieve sustainable agricultural development, yet the potential for crop rotational diversity to contribute to environmental benefits in soils remains uncertain. Here, we investigated the effects of different crop rotation patterns on the physicochemical properties, enzyme activities, microbial biomass and microbial communities in soils from field experiments. Crop rotation patterns included (i) pure maize monoculture (CC), (ii) maize-garlic (CG), (iii) maize-rape (CR) and (iv) maize-annual ryegrass for one year (Cir1), two years (Cir2) and three years (Cir3). Our results showed that soil physicochemical properties varied in all rotation patterns, with higher total and available phosphorus concentrations in CG and CR and lower soil organic carbon and total nitrogen concentrations in the maize-ryegrass rotations compared to CC. Specifically, soil fertility was ranked as CG > Cir2 > CR > Cir3 > CC > Cir1. CG decreased enzyme activities but enhanced microbial biomass. Cir2 decreased carbon (C) and nitrogen (N) acquiring enzyme activities and soil microbial C and N concentrations, but increased phosphorus (P) acquiring enzyme activities and microbial biomass P concentrations compared to CC. Soil bacterial and fungal diversity (Shannon index) were lower in CG and Cir2 compared to CC, while the richness (Chao1 index) was lower in CG, CR, Cir1 and Cir2. Most maize rotations notably augmented the relative abundance of soil bacteria, including Chloroflexi, Gemmatimonadetes and Rokubacteria, while not necessarily decreasing the abundance of soil fungi like Basidiomycota, Mortierellomycota and Anthophyta. Redundancy analysis indicated that nitrate-N, ammonium-N and microbial biomass N concentrations had a large impact on soil bacterial communities, whereas nitrate-N and ammonium-N, available P, soil organic C and microbial biomass C concentrations had a greater effect on soil fungal communities. In conclusion, maize rotations with garlic, rape and ryegrass distinctly modify soil properties and microbial compositions. Thus, we advocate for garlic and annual ryegrass as maize cover crops and recommend a two-year rotation for perennial ryegrass in Southwest China.

Straw incorporation and nitrogen reduction effect on the uptake and use efficiency of nitrogen as well as soil CO2 emission of relay strip intercropped soybean

Intercropping can increase crop N uptake and reduce carbon emissions. However, the effects of straw incorporation and N reduction on N use and carbon emissions in intercropping are still unclear. We explored the mechanism of N uptake, N use efficiency, and CO₂ emissions in the wheat-maize-soybean relay strip intercropping system. A two-year field experiment was conducted with two straw managements, i.e., wheat straw incorporation (SI) and straw removal (SR), and four N application levels of soybean, i.e., 60 (N60), 30 (N30), 15 (N15), and 0 kg N ha^-1 (N0). We assessed soil properties, CO₂ emissions, and characteristics of roots, nodules, and aboveground N uptake of intercropped soybean. Results showed that geometry mean diameter of aggregate, soil porosity, soil total N, and soil urease activity were notably greater in SI than in SR. N input reduced from N60 to N30 did not significantly affect the soil total N content and urease activity in SI. The root length, root surface area, root volume, root biomass, root bleeding intensity, and inorganic N content of bleeding sap were greater in SI than in SR. In the SI, although the root length and surface area peaked at N60, the root biomass and inorganic N content of bleeding sap were insignificant between N60 and N30. The nodule number, nodule dry weight, nodule nitrogenase activity, and nodule nitrogen fixation potential in SI were notably increased compared with SR. The nodule nitrogen fixation potential in SI notably increased with the decrease of N input at the R3 stage, but it peaked in N30 at the R5 stage. On average, the aboveground N uptake and nitrogen recovery efficiency (RE) was notably higher by 43.7% and 76.8% in SI than in SR. SI+N30 achieved the greatest aboveground N uptake and RE. The CO₂ emission and accumulated CO₂ emission were notably greater in SI than in SR, and the accumulated CO₂ emission of SI was the lowest with N30 input. In conclusion, SI+N30 promoted N uptake and utilization efficiency with reduced CO₂ emissions during the soybean cropping season. It provides a potential strategy for sustainable agricultural development in intercropping systems.

Straw Return and Nitrogen Fertilization to Maize Regulate Soil Properties, Microbial Community, and Enzyme Activities Under a Dual Cropping System

Soil sustainability is based on soil microbial communities’ abundance and composition. Straw returning (SR) and nitrogen (N) fertilization influence soil fertility, enzyme activities, and the soil microbial community and structure. However, it remains unclear due to heterogeneous composition and varying decomposition rates of added straw. Therefore, the current study aimed to determine the effect of SR and N fertilizer application on soil organic carbon (SOC), total nitrogen (TN), urease (S-UE) activity, sucrase (S-SC) activity, cellulose (S-CL) activity, and bacterial, fungal, and nematode community composition from March to December 2020 at Guangxi University, China. Treatments included two planting patterns, that is, SR and traditional planting (TP) and six N fertilizer with 0, 100, 150, 200, 250, and 300 kg N ha^–1. Straw returning significantly increased soil fertility, enzymatic activities, community diversity, and composition of bacterial and fungal communities compared to TP. Nitrogen fertilizer application increased soil fertility and enzymes and decreased the richness of bacterial and fungal communities. In SR added plots, the dominated bacterial phyla were Proteobacteria, Acidobacterioia, Nitrospirae, Chloroflexi, and Actinobacteriota; whereas fungal phyla were Ascomycota and Mortierellomycota and nematode genera were Pratylenchus and Acrobeloides. Co-occurrence network and redundancy analysis (RDA) showed that TN, SOC, and S-SC were closely correlated with bacterial community composition. It was concluded that the continuous SR and N fertilizer improved soil fertility and improved soil bacterial, fungal, and nematode community composition.

Effects of straw and straw-derived biochar on bacterial diversity in soda saline-alkaline paddy soil

Purpose

In order to provide a scientific basis for the improvement of soda saline-alkaline paddy soil, the pot experiment was performed to explore the effects of rice straw and straw-derived biochar on the diversity of soil bacteria and community structure in soda saline-alkaline soil.

Methods

The experiment was four gradients of straw return (3 (RS1), 7.5 (RS2), 12 (RS3), and 16.5 (RS4) t/hm2) and four gradients of biochar return (3 (RB1), 7.5 (RB2), 12 (RB3), and 16.5 (RB4) t/hm2), using 0 t/hm2 as a control (CK). After 5 consecutive years of measuring straw returns, high-throughput sequencing was used to determine the relative abundance, alpha diversity, and changes in the community structure of soil bacteria.

Result

Our results demonstrated that straw return significantly increased the relative abundance of Bacteroidetes, Firmicutes, and Sphingomonas and significantly reduced the relative abundance of Acidobacteria, Actinobacteria, Gemmatimonadetes, Parcubacteria, Anaeromyxobacter, Pontibacter, uncultured_bacterium_f_Draconibacteriaceae, and Bryobacter. Straw-derived biochar return significantly increased the relative abundance of uncultured_bacterium_f_Draconibacteriaceae and significantly reduced the relative abundances of Actinobacteria, Gemmatimonadetes, Thiobacillus, and Anaeromyxobacter, indicating that both straw and its associated biochar return changed the relative abundance of the phyla and genera of some bacteria. Straw return affected bacteria phylum and genus more than straw-derived biochar. With the exception of the 16.5 t/hm2 straw return, which reduced bacterial richness, the treatments did not significantly impact alpha diversity. Compared with straw-derived biochar return, straw return significantly changed the bacterial community structure, and the higher the straw return, the higher the impact on the bacterial community structure. Redundancy analysis (RDA) demonstrated that there was a significant correlation between the physicochemical properties of the soil and the community structure of its bacteria. A Mantel test demonstrated that the content of available phosphorus, available potassium, and organic matter was all important environmental factors affecting community structure.

Conclusion

We speculate that straw return regulates the physicochemical properties of the soil, which affects the bacterial community structure.

Effects of straw return and straw biochar on soil properties and crop growth: A review

Straw return is an effective method for disposing agricultural residues. It not only utilizes agricultural waste but also improves soil. In the current review, different crop straw and its characteristics were highlighted, and patterns of straw return were explored (including straw return, straw biochar return, and their combined with fertilizer return), as well as their environmental impacts were outlined. In addition, the effects of straw return and straw biochar amendment on soil properties [e.g., pH, soil organic carbon (SOC), soil nitrogen (N)/phosphorus (P)/potassium (K), soil enzyme activities, and soil microbes] were discussed. Information collected from this review proposed that straw return and straw biochar return or in combination with fertilizer is an applicable way for improving soil fertility and enhancing crop production. Straw return is beneficial to soil physicochemical properties and soil microbial features. The rice straw has positive impacts on crop growth. However, there are different climate types, soil types and crops in China, meaning that the future research need long-term experiment to assess the complex interactions among straw, soil, and plant eco-systems. Accordingly, this review aims to provide available information on the application of straw return in terms of different patterns of its to justify and to expand their effective promotion.

No tillage and residue mulching method on bacterial community diversity regulation in a black soil region of Northeastern China

Soil microorganisms are important components of agricultural ecosystems; they are important in agricultural soil nutrient cycle and are easily affected by soil tillage. The response of soil microbial community to tillage is very complex, and the effect of the no tillage and residue mulching method on soil microbial diversity remains unclear. In 2019, the soil was collected from an experimental field after 10 years of continuous cultivation in the black soil area of the Sanjiang Plain in Northeastern China. In this study, the diversity and composition of the soil bacterial community and their relationship with soil properties were explored via high-throughput sequencing under no tillage with four residue mulching treatments. No tillage with 60% residue mulching (NTR3) significantly increased the alpha diversity of the rhizosphere soil bacteria and changed the composition of the bacterial community-consistent with changes in soil physicochemical properties. Proteobacteria, Acidobacteria, and Actinobacteria were the dominant phyla in the sample soil. Soil physicochemical properties explained 80.6% of the changes in soil diversity and composition, of which soil organic carbon, soil pH, and soil temperature were the principal contributors. Our results suggest that no tillage and residue mulching is conducive to increasing soil organic carbon and soil nutrient content, which is a beneficial conservation tillage measure for black soil protection in Sanjiang Plain of Northeast China. The no tillage with residue mulching, especially 60% residue mulching, alters soil bacterial community and highlights the importance of soil physicochemical properties in shaping the diversity and composition of the soil bacterial community. Our findings contribute to a broad understanding of the effects of no tillage and residue mulching on bacterial community differences and provide a scientific basis for the optimization of no tillage measures and sustainable utilization of the black soil of the Sanjiang Plain in Northeastern China.

Long-term effects of maize straw return and manure on the microbial community in cinnamon soil in Northern China using 16S rRNA sequencing

Excessive use of chemical fertilizers in agricultural practices have demonstrated a significant impact on microbial diversity and community in soil by altering soil physical and chemical properties, thereby leading to a certain degree of soil salinization and nutritional imbalances. As an organic amendment, maize straw has been widely used to improve soil quality; however, its effect on the soil bacterial community remains limited in Calcarie-Fluvie Cambisols soil in semi-humid arid plateau of North China. In the present experiment, we investigated the effects of continuous straw utilization and fertilization on bacterial communities in Shouyang, Shanxi province, China. Soil samples were collected from 5 different straw utilization and fertilization modes in the following ways: straw mulching (SM), straw crushing (SC), cattle manure (CM), in which way straw is firstly used as silage and then organic fertilizer, control with no straw return (NSR), and control without fertilizers (CK), same amount of N+P fertilizer was applied to the regimes except CK. High-throughput sequencing approaches were applied to the V3-V4 regions of the 16S ribosomal RNA for analysis of the bacterial abundance and community structures. Different long-term straw returning regimes significantly altered the physicochemical properties and bacterial communities of soil, among which CM had the most significant effects on soil fertility and bacterial diversity. Proteobacteria, Actinobacteria, Chloroflexi, Acidobacteria, and Gemmatimonadetes were consistently dominant in all soil samples, and Redundancy analysis (RDA) showed significant association of total nitrogen (TN), total phosphorus (TP) and available potassium (AK) with alternation of the bacterial community. Cattle manure had the most beneficial effects on soil fertility and bacterial diversity among different straw utilization and fertilization modes.

Elevated CO2 weakens the shift in bacterial community structure in response to 8-year soybean straw return in the same experiment

A potentially important source for soil organic carbon (SOC) in the agricultural ecosystem is straw, straw return has been shown to affect soil bacterial communities. Facing global climate change, the response of bacterial communities to straw return will change at CO2 enrichment. In this study, we investigate the changes of bacterial communities in response to straw return (+straw) at elevated CO2 (eCO2, 700 ppm) in a long-term field experiment of northeast China. Soil samples were taken in the eighth year and analyzed by high throughput sequencing. Soil bacterial communities exhibited distinct clustering according to straw return and eCO2, while eCO2 shortened the distance of clustering between straw return and not. The relative abundances of 10 genera (Acidobacteria_norank, Candidatus_Solibacter, Gaiella, Nocardioides, Streptomyces, C0119_norank, Roseiflexus, Gemmatimonas, Mizugakiibacter and Rhodanobacter) were significantly affected by the interaction of straw × eCO2. In addition, straw return significantly decreased the relative abundances of Gaiellales_norank, Blastococcus, Psedarthrobacter, and Bacillus and increased that of Geminatimonadaceae_norank, Tepidisphaeraceae, Nitrosomonadaceae_norank, and SC-I-84_norank. These differential responses of genera abundances are illustrative of the susceptibility of bacterial communities and indicate their importance in evaluating the fate of exogenous C. The Clusters of Orthologous Groups (COG) analysis showed that straw return had a greater effect on the relative abundances of COG categories than eCO2. The present results point to the need to focus more strongly on the turnover and storage of straw-C during a chronic straw return in the future.

Bacteria with Different Assemblages in the Soil Profile Drive the Diverse Nutrient Cycles in the Sugarcane Straw Retention Ecosystem

Straw retention, an alternative to artificial fertilization, commonly mitigates soil degradation and positively affects soil fertility. In this study, we investigated the succession of soil bacteria during two sugarcane straw retention treatments (control (CK) and sugarcane straw retention (SR)) and at four depths (0–10, 10–20, 20–30, and 30–40 cm) in fallow soil in a sugarcane cropping system. Using an Illumina MiSeq (16S rRNA) and soil enzyme activity, we explored the SR influence on soil bacterial communities and enzyme activities and its inclusive impact on soil fertility, with an emphasis on topsoil (0–10 cm) and subsoil (10–40 cm). Our results show that SR effectively improved soil fertility indicators (C, N, and P), including enzyme activities (C and N cycling), throughout the soil profile: these soil parameters greatly improved in the topsoil compared to the control. Sugarcane straw retention and soil depth (0–10 cm vs. 10–40 cm) were associated with little variation in bacterial species richness and alpha diversity throughout the soil profile. Subsoil and topsoil bacterial communities differed in composition. Compared to the CK treatment, SR enriched the topsoil with Proteobacteria, Verrucomicrobia, Actinobacteria, Chloroflexi, and Nitrospirae, while the subsoil was depleted in Nitrospirae and Acidobacteria. Similarly, SR enriched the subsoil with Proteobacteria, Verrucomicrobia, Actinobacteria, Chloroflexi, Gemmatimonadetes, and Bacteroidetes, while the topsoil was depleted in Acidobacteria, Gemmatimonadetes, and Planctomycetes compared to the CK. At the genus level, SR enriched the topsoil with Gp1, Gp2, Gp5, Gp7, Gemmatimonas, Kofleria, Sphingomonas, and Gaiella, which decompose lignocellulose and contribute to nutrient cycling. In summary, SR not only improved soil physicochemical properties and enzyme activities but also enriched bacterial taxa involved in lignocellulosic decomposition and nutrient cycling (C and N) throughout the soil profile. However, these effects were stronger in topsoil than in subsoil, suggesting that SR enhanced fertility more in topsoil than in subsoil in fallow land.

Wheat Straw Return Influences Nitrogen-Cycling and Pathogen Associated Soil Microbiota in a Wheat-Soybean Rotation System

Returning straw to soil is an effective way to sustain or improve soil quality and crop yields. However, a robust understanding of the impact of straw return on the composition of the soil microbial communities under field conditions has remained elusive. In this study, we characterized the effects of wheat straw return on soil bacterial and fungal communities in a wheat–soybean rotation system over a 3-year period, using Illumina-based 16S rRNA, and internal transcribed region (ITS) amplicon sequencing. Wheat straw return significantly affected the α-diversity of the soil bacterial, but not fungal, community. It enhanced the relative abundance of the bacterial phylum Proteobacteria and the fungal phylum Zygomycota, but reduced that of the bacterial phylum Acidobacteria, and the fungal phylum Ascomycota. Notably, it enriched the relative abundance of nitrogen-cycling bacterial genera such as Bradyrhizobium and Rhizobium. Preliminary analysis of soil chemical properties indicated that straw return soils had significantly higher total nitrogen (TN) contents than no straw return soils. In addition, the relative abundance of fungal genera containing pathogens was significantly lower in straw return soils relative to control soils, such as Fusarium, Alternaria, and Myrothecium. These results suggested a selection effect from the 3-year continuous straw return treatment and the soil bacterial and fungal communities were moderately changed.