Long-term surface composts application enhances saline-alkali soil carbon sequestration and increases bacterial community stability and complexity

Microbial network-driven remediation of saline-alkali soils by salt-tolerant plants

Salt-tolerant plants (STPs) play an important role in saline-alkali soil remediation, but their interaction with soil microorganisms remain incompletely elucidated. This study explored the effects on microbial community structure, function, and soil quality in saline-alkali land of four treatments: no plant (CK), Triticum aestivum L. (TA), Tamarix chinensis Lour. (TC), and Hibiscus moscheutos Linn. (HM). The results indicated that the planting of TC, TA, and HM effectively reduced soil electrical conductivity (EC) by 82.9, 88.3, and 86.2%, respectively. TC and TA significantly decreased the pH from 8.79 to 8.35 and 8.06, respectively, (p < 0.05). Moreover, the nutrient content and enzymatic activities were enhanced. Notably, TA exhibited the most significant soil nutrient improvement. STPs also substantially altered the microbial community structure and function, with TC increasing bacterial richness (ACE and Chao1 indices) compared to other treatments (p < 0.05). Moreover, TA significantly promoted the relative abundance of unclassified_Gemmatimonadaceae, unclassified_Vicinamibacterales, and Mortierella (p < 0.05). A major innovation of this study is using network analysis to explore microbial interactions, revealing how STPs enhance microbial network complexity. This approach identified Sphingomonas as a key taxon in TA soils, shedding light on the microbial dynamics of soil remediation. Additionally, partial least squares path model (PLS-PM) showed that soil quality improvements were primarily driven by shifts in bacterial composition, offering a novel mechanistic framework for understanding microbial contributions to soil restoration. This research advances the understanding of microbial-plant interactions and underscores the innovative application of network analysis in phytoremediation, offering valuable insights for future soil restoration strategies.

Organic amendments enhance rhizosphere carbon stabilization in macroaggregates of saline-sodic soils by regulating keystone microbial clusters

Photosynthetic carbon plays a pivotal role in soil organic carbon (SOC) sequestration in agricultural soils. However, how organic amendments regulate photosynthetic carbon accumulation through multitrophic microbes at the aggregate scale, especially the core microbiota, remains unclear. Here, we conducted a13CO2-labeled rhizo-box experiment on a saline-sodic soil with five treatments: no fertilizer (Ctrl), chemical fertilizer, pig manure (PM), milk vetch straw (MV), and vermicompost. The 13C-SOC in the MV and PM treatments was 2.4 and 1.4 times greater than that in the Ctrl, respectively. Compared with the Ctrl, organic amendments significantly increased 13C-macroaggregate-associated OC (13C-Macro-OC) by 122.4-615.8 % and 13C-mineral-associated OC (13C-MAOC) by 123.6-564.5 % in macroaggregates (> 0.25 mm). The 13C-Macro-OC was significantly positively correlated with biodiversity, the relative abundances of bacteria (mainly Acidobacteriota and Firmicutes) and fungi (mainly Ascomycota and Mucoromycota) in the keystone microbial cluster, network complexity, and the proportion of negative cross-trophic associations. Structural equation modeling revealed that the root trait-induced core microbiota, following organic amendments, affected photosynthetic carbon accumulation via 13C-MAOC in macroaggregates. In summary, our findings highlight the positive effects of milk vetch straw on SOC accumulation and provide a theoretical basis for the targeted regulation of SOC accumulation in saline-sodic soils through organic amendments.

Application of compost amended with biochar on the distribution of antibiotic resistance genes in a soil-cucumber system-from the perspective of high-dose fertilization

The transfer of antibiotic resistance genes (ARGs) from soils to vegetables negatively impacts human health. This study explored the effects of the high-dose (18.73 t/ha) application of traditional compost (TC) and composts produced through the co-composting of traditional materials with large-sized (5-10 mm) biochar-amended compost (LBTC) or small-sized (< 0.074 mm) biochar-amended compost (SBTC) on the distribution of ARGs in a soil-cucumber system were explored. Results indicated that the SBTC group had the highest soil nitrogen, phosphorus, and potassium contents, followed by the LBTC, TC, and control treatment groups. These findings aligned with the quality and weight of harvested cucumbers. Bacterial community diversity decreased in compost-fertilized soils. Compared with their preexperimental values in soils, the total absolute abundances of ARGs and mobile genetic elements (MGEs) increased by 23.88 and 6.66 times, respectively, in the control treatment group; by 5.59 and 5.23 times, respectively, in the TC group; by 5.50 and 1.81 times, respectively, in the LBTC group; and by 5.49 and 0.47 times, respectively, in the SBTC group. Compared with those in the control treatment group, the absolute abundance of ermB, ermT, gyrA, qnrS, tetC, and intI1 decreased by 6-100% in the soil of the SBTC group. Compost application to soils significantly decreased ARG abundance in cucumbers; SBTC had the most significant effect and reduced the number of host bacteria at the phylum level from four to three. Nutrient levels in soils were important factors influencing the migration of ARGs from soils to cucumbers. In summary, when compared to other composts, the high-dose (18.73 t/ha) application of SBTC is more effective at reducing the risk of the accumulation and transfer of ARGs in the soil-cucumber system.

Bacillus halophilus BH-8 Combined with Coal Gangue as a Composite Microbial Agent for the Rehabilitation of Saline-Alkali Land

Saline-alkali land represents a crucial reserve of arable land essential for ensuring food security. However, there remains a significant deficiency in converting saline-alkali land into productive cultivated or grazing areas. Microbial agents hold substantial potential for the reclamation of saline-alkali soils. In this study, a moderately halophilic bacterium, Bacillus halophilus BH-8, was screened from coastal saline soil. We combined strain BH-8 with coal gangue to create a composite microbial agent, which was shown to effectively increase the levels of available nitrogen, available phosphorus, available potassium, and organic matter, while reducing the pH value of saline-alkali soils. Moreover, it significantly enhanced the activity of various enzymes and altered the microbial community composition in the soil, notably increasing the abundance of Pseudomonas and Bacteroidota. These results demonstrate the application value of this composite microbial agent for rehabilitating saline-alkali land and highlight the potential of the BH-8 strain as a promising candidate for microbial agent research.

Metagenomic analysis reveal the phytoremediation effects of monocropping and intercropping of halophytes Halogeton glomeratus and Suaeda glauca in saline soil of Northwestern China

AIMS

Planting halophytes is a widely used method of phytoremediation for saline soils. The succulent halophytes Halogeton glomeratus and Suaeda glauca are widely used for remediation of saline soil in the arid region of Northwestern China. However, whether intercropping of H. glomeratus and S. glauca can increase the improvement effect for saline soil is yet to be proved.

MATERIALS AND METHODS

Therefore, this study analyzed three phytoremediation planting modes: monocropping of H. glomeratus (Hg), monocropping of S. glauca (Sg), and H. glomeratus and S. glauca intercropping (Hg||Sg). These were applied in field experiments, with biomass and soil physicochemical properties measured for each treatment, and the mechanism was analyzed using macrogenomics.

RESULTS

After harvesting the halophytes after one season, the Hg treatment had the highest dry biomass and soil total dissolved salt content was reduced; correspondingly, soil pH were decreased and soil organic matter content were increased. The results showed that Actinobacteria, Acidobacteria and Proteobacteria were the dominant phylum under the four treatments. This suggests that Hg treatment was more capable of producing microorganisms favorable to saline soil remediation.

CONCLUSIONS

Thus, H. glomeratus monocropping is a more effective phytoremediation strategy for saline soil in the dry zone of Northwestern China.

Variation of bacterial community diversity and composition in saline-alkali soils reclaimed with flood irrigation and crop cultivation is driven by salinity and edaphic factors

Reclamation is crucial for improving the fertility and productivity of saline-alkali soils, but the evolution of soil bacterial communities during the course of reclamation, which is an important feedback of soil micro-ecosystem, has received little attention. This study was conducted to investigate the variation of bacterial community diversity and composition in reclaimed saline-alkali soils based on space-for-time substitution, elucidate the underlying ecological mechanisms of bacterial community assembly processes, and identify the key driving factors of bacterial community evolution. The soil bacterial communities in undeveloped saline-alkali land and farmlands with different reclamation history (1-4, 5-6, and 10-25 years) in the Yellow River Delta, China, was analyzed by 16S rRNA gene amplicon sequencing. Soil bacterial diversity was found to increase significantly with reclamation history, and the entire bacterial community composition varied remarkably in the saline-alkali soils at different stages of reclamation. Halophilic and halotolerant bacteria dominated in the soils of undeveloped saline-alkali land (33.7 %), but their abundance diminished largely in the reclaimed soils. Analysis of bacterial community assembly processes suggested that heterogeneous selection dominated the change of bacterial communities in the saline-alkali soils that had been reclaimed for 1-4 years (52.8 %), 5-6 years (93.1 %), and 10-25 years (94.4 %). Salinity, soil organic carbon, pH, and moisture content were found to be the key environmental factors driving the evolution of bacterial communities in the reclaimed saline-alkali soils. While salinity directly shaped the bacterial community diversity, the other key drivers primarily governed the composition of bacterial communities in the saline-alkali soils during reclamation. These findings shed light on the probable ecological mechanisms of assembly processes and the environmental factors driving the soil bacterial communities during reclamation of saline-alkali lands, which could help better understand the evolution of soil bacterial communities under declining saline stress and optimize strategies to improve the agroecosystem health of saline-alkali lands.

Compost mediates the recruitment of core bacterial communities in alfalfa roots to enhance their productivity potential in saline-sodic soils

Introduction

Composting is one of the effective environmental protection and sustainable measures for improving soil quality and increasing crop yield. However, due to the special physical and chemical properties of saline-sodic soil and the complex rhizosphere microecological environment, the potential mechanism of regulating plant growth after applying compost in saline-sodic soil remains elusive.

Methods

Here, we investigated the effects of different compost addition rates (0, 5, 15, 25%) on plant growth traits, soil chemical properties, and rhizosphere bacterial community structure.

Results

The results showed that compost promoted the accumulation of plant biomass and root growth, increased soil nutrients, and enhanced the diversity and complexity of the rhizosphere bacterial communities. Moreover, the enriched core bacterial ASVs (Amplicon Sequence Variants) in compost treatment could be reshaped, mainly including dominant genera, such as Pseudomonas, Devosia, Novosphingobium, Flavobacterium, and Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium. The functions of these ASVs were energy resources and nitrogen cycle functions, suggesting the roles of these ASVs in improving plant root nutrient resource acquisition for alfalfa growth. The contents of available potassium, available phosphorus, total nitrogen, and organic carbon of the soil surrounding the roots, the root length, root surface area, root volume, and root tips affected the abundance of the core bacterial ASVs, and the soil chemical properties contributed more to the effect of plant biomass.

Discussion

Overall, our study strengthens the understanding of the potentially important taxa structure and function of plant rhizosphere bacteria communities, and provides an important reference for developing agricultural microbiome engineering techniques to improve root nutrient uptake and increase plant productivity in saline-sodic soils.

Effects of understory intercropping with salt-tolerant legumes on soil organic carbon pool in coastal saline-alkali land

Phytoremediation through understory intercropping with salt-tolerant legumes (forest-green manure composite patterns) efficiently and sustainably enhances saline-alkali soils, while significantly improving the stability of monoculture forest ecosystems and the efficacy of soil upgrades. However, exactly how forest-green manure patterns regulate the dynamics of the soil organic carbon (SOC) pool and related mechanisms remain unclear. For this study, a pure forest was used as the control, and three leguminous herbaceous plants (M. sativa, S. cannabina, and C. pallida) were intercropped under two forest stand types (T. hybrid 'Zhongshanshan' and C. illinoensis). The variable characteristics and control factors of SOC and its components under different patterns were elucidated by analyzing the soil physical and chemical properties, enzyme activities, and microbial communities. The results revealed that the composite pattern improved soil salinization and increased the activities of β-1,4-glucosidase, polyphenol oxidase, peroxidase (PER), invertase (INV), and urease, as well as the carbon pool management index and the proportion of active organic carbon. At the T. hybrid 'Zhongshanshan' experimental site, planting M. sativa effectively increased the total carbon (TC) content. The ammonium nitrogen, soil moisture content, total phosphorus, alkaline phosphatase, PER, and polyphenol oxidase were the primary driving factors that affected the SOC pool. At the C. illinoensis experimental site, S. cannabina planting was observed to increase the TC content, with the TC, exchangeable Na+, β-1,4-N-acetylglucosaminidase, and INV being the main driving factors that impacted the SOC pool. The composite pattern can indirectly influence the SOC pool by altering the soil properties to regulate the microbial community. Further, it was found that soil inorganic carbon (SIC) was the main contributor to increasing the soil carbon pool following the short-term planting of legumes; thus, there may have been a transfer process that occurred from the SOC to SIC. Our study suggests that the forest-green manure pattern has more positive effects on improving soil quality and the carbon pool in saline-alkali land.

Core Bacterial Taxa Determine Formation of Forage Yield in Fertilized Soil

Understanding the roles of core bacterial taxa in forage production is crucial for developing sustainable fertilization practices that enhance the soil bacteria and forage yield. This study aims to investigate the impact of different fertilization regimes on soil bacterial community structure and function, with a particular focus on the role of core bacterial taxa in contributing to soil nutrient content and enhancing forage yield. Field experiments and high-throughput sequencing techniques were used to analyze the soil bacterial community structure and function under various fertilization regimes, including six treatments, control with no amendment (CK), double the standard rate of organic manure (T01), the standard rate of organic manure with nitrogen input equal to T04 (T02), half the standard rate of inorganic fertilizer plus half the standard rate of organic manure (T03), the standard rate of inorganic fertilizer reflecting local practice (T04), and double the standard rate of inorganic fertilizer (T05). The results demonstrated that organic manure treatments, particularly T01, significantly increased the forage yield and the diversity of core bacterial taxa. Core taxa from the Actinomycetota, Alphaproteobacteria, and Gammaproteobacteria classes were crucial in enhancing the soil nutrient content, directly correlating with forage yield. Fertilization significantly influenced functions relating to carbon and nitrogen cycling, with core taxa playing central roles. The diversity of core microbiota and soil nutrient levels were key determinants of forage yield variations across treatments. These findings underscore the critical role of core bacterial taxa in agroecosystem productivity and advocate for their consideration in fertilization strategies to optimize forage yield, supporting the shift towards sustainable agricultural practices.

How to make lunar soil suitable for cultivation? - A review

The investigation of lunar soil encompasses extensive periods, employs many improvement methods, and has generated several simulants. The improvement of lunar soil has recently garnered growing interest as an aspect of In-Situ Resource Utilization (ISRU) for regolith. It is crucial to clarify the challenges of utilizing lunar soil as a planting substrate to develop more effective techniques. This review presents a comprehensive analysis of research on improving lunar soil properties, highlights the disparities in mineral composition between real lunar soil (also called regolith) and simulated lunar soil, then details their deficiencies as planting substrates. Following an investigation of existing improvement methods, a dilemma of metals、salt precipitation and high pH caused by adding organic matter alone was noted, while the function of microbes (bacteria, algae, and lichens) in improvement processes was assessed. Finally, we present a perspective on future the lunar soil plantable research development based on the Bioregenerative Life Support System (BLSS). This review aims to promote the engineering application of lunar soil improvements and sustainable development. We hope that one day, regolith will enable plants to flourish on the Moon.

Cultivating a sustainable future in the artificial intelligence era: A comprehensive assessment of greenhouse gas emissions and removals in agriculture

Agriculture is a leading sector in international initiatives to mitigate climate change and promote sustainability. This article exhaustively examines the removals and emissions of greenhouse gases (GHGs) in the agriculture industry. It also investigates an extensive range of GHG sources, including rice cultivation, enteric fermentation in livestock, and synthetic fertilisers and manure management. This research reveals the complex array of obstacles that are faced in the pursuit of reducing emissions and also investigates novel approaches to tackling them. This encompasses the implementation of monitoring systems powered by artificial intelligence, which have the capacity to fundamentally transform initiatives aimed at reducing emissions. Carbon capture technologies, another area investigated in this study, exhibit potential in further reducing GHGs. Sophisticated technologies, such as precision agriculture and the integration of renewable energy sources, can concurrently mitigate emissions and augment agricultural output. Conservation agriculture and agroforestry, among other sustainable agricultural practices, have the potential to facilitate emission reduction and enhance environmental stewardship. The paper emphasises the significance of financial incentives and policy frameworks that are conducive to the adoption of sustainable technologies and practices. This exhaustive evaluation provides a strategic plan for the agriculture industry to become more environmentally conscious and sustainable. Agriculture can significantly contribute to climate change mitigation and the promotion of a sustainable future by adopting a comprehensive approach that incorporates policy changes, technological advancements, and technological innovations.