The potential and prospects of modified biochar for comprehensive management of salt-affected soils and plants: A critical review

Boron-induced phenylpropanoid metabolism, Na+/K+ homeostasis and antioxidant defense mechanisms in salt-stressed soybean seedlings

Boron (B)-induced alleviation of salt stress in plants have been examined in some details, but the mechanisms underlying these processes remain largely unexplored. In this study, soybean seedlings were irrigated with nutrient solution containing either 0 or 100 mM NaCl with two B levels. The results showed that salt stress adversely inhibited plant growth-related parameters and photosynthetic rate, caused oxidative damage in terms of higher malondialdehyde (MDA) and reactive oxygen species (ROS) levels. Co-treatment with B and salt causes a decrease in overall Na+ content in plant, with increased in Na+ content in root and root cell wall (CW) and a reduction in Na+ translocation factor. Additionally, B supplementation boosted antioxidant enzyme activities, and reduced MDA, H2O2, and osmotic substance levels under salt stress. Boron specifically induced the phenylpropanoid metabolism pathway, enhanced the antioxidants accumulation such as cinnamic acid, coumarin, and sinapic acid, as well as flavonoids like glycine and genistein, collectively reduced salt-induced ROS accumulation. Taken together, B mitigates salt stress by enhancing root antioxidant defenses and activating the phenylpropanoid metabolism pathway which reduces ROS level. Boron enhanced root retention of Na+ to alleviate oxidative damage caused by Na+ accumulation in leaf, ultimately improves photosynthesis and promotes seedlings growth.

Biochar amendment modulate microbial community assembly to mitigate saline-alkaline stress across soil depths

While microbial community assembly in saline-alkali topsoils is well-documented, distribution patterns across biochar application depths and soil layers remain unclear. This incubation study evaluated five treatment: no biochar (CK), homogeneous application (EB), and concentrated applications in upper (FB: 0-10 cm), middle (MB: 10-20 cm), or bottom layers (DB: 20-30 cm). Biochar application significantly accelerated vertical salt migration, with FB inducing 45.55 % and 61.01 % increases in water-soluble Na+ and Cl- accumulation in the bottom layer. Microbial network complexity and interspecies interactions were highest in the upper layer (edges: 926), contrasting sharply with simplified communities in deeper layer (edges ≤552). Community assembly across layers was primarily driven by salt gradients, with deep-layer communities dominated by salt-tolerant taxa (such as Halomonas and Desulfobacterota). Among treatments, FB led to the highest biomarker abundance and α-diversity. Mechanistically, FB mitigated microbial diversity loss in mid-deep layers by establishing a symbiotic consortium of salt-tolerant keystone taxa (Bacillus-Pseudomonas-Ascomycota), which enhanced stress resilience via cross-feeding. These findings demonstrate that stratified biochar application (FB) optimizes salt redistribution while fostering stress-adapted microbial consortia across soil profiles, offering a targeted strategy for saline-alkali soil remediation.

"Nano-calcium L-Aspartate enhances rice tolerance to arsenic toxicity by improving nitrogen metabolism, cell wall sequestration, and antioxidant system"

Rice is one of the major sources of human exposure to arsenic (As), and its contamination is a critical issue for crop productivity and human health. Herein, we investigated how nano-calcium L-aspartate (nano-Ca) nanoparticles alleviate As-induced toxicity in rice (Oryzae sativa L.) seedlings. The results showed that As stress restricted rice growth and increased the concentration of As in roots and shoots. Application of nano-Ca markedly improved seedling growth, including biomass, photosynthetic pigment content, and antioxidant enzyme activity. As a result, Nano-Ca decreased As concentrations in shoots and roots by 67.04 % and 22.78 %, respectively, primarily due to the increasing accumulation of As in pectin and hemicellulose. Furthermore, nano-Ca elevated the activity of nitrogen-metabolizing enzymes. The treatment also promoted demethylation of pectin, which enhanced its As-binding capability. Additionally, nano-Ca enhanced proline metabolism, also provided antioxidant defenses, and regulated calcium homeostasis, which help mitigate oxidative damage characteristics like malondialdehyde and hydrogen peroxidation. As these findings demonstrated, nano-Ca could be an efficient, friendly means of alleviating As toxicity in rice, offering an environmentally sustainable option for agricultural strategies in the arsenic-contaminated areas.

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.

Exogenous proline enhances salt acclimation in soybean seedlings: Modifying physicochemical properties and controlling proline metabolism through the ornithine-glutamate dual pathway

Soil salinization has emerged as a major factor negatively affecting soil quality and plant productivity. Proline, functioning as an osmotic regulator, has been proposed as an effective strategy for enhancing plant tolerance to salt stress. This study aimed to investigate the effects of exogenous proline on salt tolerance in soybeans. A hydroponic experiment was conducted with different salt treatments (without NaCl, -NaCl; with 100 mM NaCl, +NaCl) and with or without 150 mM proline (+Pro, -Pro). The results showed that proline application alleviated salt stress-induced reductions in plant growth, photosynthetic parameters, and chlorophyll content while aiding recovery from leaf chlorosis. Proline treatment improved ion homeostasis by reducing Na+ levels and increasing K+ and Ca2+ contents in the leaves. Salt stress increased malondialdehyde (MDA) and reactive oxygen species (ROS) levels, along with leaf peroxidase (POD) and catalase (CAT) activities, while decreasing superoxide dismutase (SOD) activity. Moreover, salt stress obviously enhanced proline accumulation, accompanied by increases in glutamate (Glu), glutamate-1-semialdehyde (GSA), and pyrroline-5-carboxylate (P5C) content, as well as the activities of pyrroline-5-carboxylate synthase (P5CS) and pyrroline-5-carboxylate reductase (P5CR) in the glutamate pathway, while reducing proline dehydrogenase (ProDH) activity. Exogenous proline treatment further elevated proline content and increased key substances and enzyme activities in both the glutamate (Glu and P5C content, P5CS and P5CR activity) and ornithine (Orn content and OAT activity) pathways while also reducing ProDH activity. Collectively, our results revealed that exogenous proline contributed to an attenuation of salt stress in soybeans by regulating both the glutamate and ornithine pathways to stimulate endogenous proline accumulation, mediate Na+/K+ homeostasis, and inhibit oxidative damage.

Combined transcriptome and metabolome analysis revealed the toxicity mechanism of individual or combined of microplastic and salt stress on maize

In saline alkaline soils, microplastics inevitably form a combined stress with NaCl to limit crop growth, but the molecular mechanisms of their toxic effects remain vague and inadequate. We analyzed the molecular mechanisms underlying the response of maize seedlings to single or combined stresses of MPs and NaCl by means of combined metabolomic and transcriptomic analyses. MPs and NaCl single or combined stresses reduced plant fresh weight by 36.78 %, 50.65 % and 73.97 %, respectively. Analyses showed 2476 differentially expressed genes (DEGs) and 809 differential metabolites (DMs) for MPs, 2306 DEGs and 901 DMs for NaCl, and 2706 DEGs and 938 DMs for the combined stresses, compared to CK. Single or combined stresses mainly altered amino acid synthesis and phenylpropane biosynthetic metabolic pathways. Stress up-regulated glutamine synthetase (glnA), alanine transaminase (ALT), aspartate aminotransferase (ASP), ornithine carbamoyl transferase (argF), and glycine hydroxymethyl transferase (SHM) genes expression and promotes glutamine, 2-oxoglutarate, glutamate, fumarate, arginine, aspartate, L-isoleucine, L-valine, and serine synthesis. NaCl stimulated phenylpropanoid biosynthesis (tyrosine, 4-coumarate, and ferulate), whereas MPs decreased it. In addition, both individual or combined NaCl and MPs stress increased the expression of cinnamyl-alcohol dehydrogenase (CAD) and cinnamoyl-CoA reductase (CCR) to promote sinapaldehyde synthesis. Our study provides a molecular perspective on the response of crops, such as maize, to individual or combined NaCl and MPs stress.

Seaweed extract combined with boron promotes the growth of sugar beet by improving the photosynthetic performance under boron deficiency

Biostimulants can improve mineral nutrient effectiveness, but the physiological mechanisms by which seaweed extract, a natural biostimulant, and boron (B) fertilizer promote the growth of sugar beet under B deficiency are not clear. In this study, B and seaweed extract were applied under B-deficiency (0.32 mg B kg-1 soil) and potentially B-deficient conditions (0.69 mg B kg-1 soil), and the growth and photochemical properties of sugar beet seedlings were investigated. The results indicated that B application alone or with seaweed extract promoted sugar beet growth, with the combined application having a significantly enhanced effect. When comparing the two soils with different B content (deficient and moderately deficient), the spray of seaweed extract under the B-deficient condition was more effective. After the addition of seaweed extract, the B content of the shoots and roots increased by 28.56% and 12.64%, respectively, under B deficiency(0.32 mg B kg-1 soil). Furthermore, the content of chlorophyll a (Chla), chlorophyll b (Chlb), and the net photosynthesis rate (Pn) increased by 8.96%, 30.57%, and 13.74%, respectively. The addition of seaweed extract significantly improved the light saturation point (Pm), with a 35.00% increase compared to the control. Additionally, it increased the quantum yield (ETO/CSm) of leaf electron transfer per unit area and reduced the absorption of light energy loss of the PS reaction center (DIO/RC) and per unit area (DIO/CSm), thereby improving photosynthetic performance and significantly increasing aboveground dry matter accumulation by 19.05%. In conclusion, seaweed extract can enhance B absorption, light energy capture and utilization ability. It provides the theoretical evidence for the regulation of B nutrition in sugar beet and the rational application of biostimulants.

Effect of soil-groundwater system on migration and transformation of organochlorine pesticides: A review

Soil is the place where human beings, plants, and animals depend on for their survival and the link between the various ecological layers. Groundwater is an important component of water resources and is one of the most important sources of water for irrigated agriculture, industry, mining and cities because of its stable quantity and quality. Soil and groundwater are important strategic resources highly valued by countries around the world. However, in recent years, the deterioration of the ecological environment of soil-groundwater caused by industrial, domestic, and agricultural pollution sources has continued to threaten human health and ecological security. Among them, organochlorine pesticides (OCPs), as typical organic pollutants, cause very serious pollution of soil and groundwater environment. However, most studies on the pollution of OCPs have focused on the aboveground or surface water environment, and little consideration has been given to the pollution and hazards of OCPs to the deep soil and groundwater environment, especially the effects of different environmental factors on the transport and transformation of OCPs in soil-groundwater. Moreover, in addition to the influence of a single factor on it, the interactions that arise between different factors cannot be ignored. This paper focuses on two major sources of OCPs in soil and groundwater environments, compiles and summarizes the effects of environmental factors such as pH, microbial communities and enzyme activities on the transport and transformation of OCPs in soil and groundwater systems, discusses the synergistic effects of individual environmental factors and others, and comprehensively analyses the effects of synergistic effects of various environmental factors on the transport and transformation of OCPs. In the context of ecological civilization construction, it provides the scientific basis and theoretical foundation for the prevention and treatment of OCPs-contaminated soil and groundwater, and puts forward new ideas and suggestions for the research and development of green, eco-friendly remediation and treatment technologies for OCPs-contaminated sites.

Effects of microplastics and salt single or combined stresses on growth and physiological responses of maize seedlings

Plastic film (mulch film) is widely used in saline and alkaline soils because it can effectively reduce salt stress damage. However, it results in the accumulation of microplastics (MPs) in the soil, which pose a threat to crop growth and production. This study investigates the effects of 50 mg l-1 MPs and 100 mM sodium chloride (NaCl), individually or in combination, on the growth and physiological characteristics of maize (Zea mays) seedlings. The results demonstrated that compared to the control, MPs and NaCl single or combined stress reduced seedling biomass and water content, and the combined stress was more serious. Stress significantly reduced N and K contents in leaves, and Na content under combined stress was lower than under single NaCl stress. Compared to single stress, the combined stress further enhanced oxidative damage by increasing H2O2 and MDA content, a disrupted chloroplast structure, and reduced chlorophyll content, ultimately leading to a decline in chlorophyll fluorescence parameters and photosynthetic efficiency. Single MPs or NaCl stress led to the accumulation of proline, soluble proteins, and soluble sugars, while the combined stresses further increased the content of these osmotic substances in plants. Moreover, single or combined stress increased the activity of CAT, POD, SOD and the content of AsA and GsH. Collectively, NaCl and MPs single or combined stress exert notable toxic effects on maize seedling growth. Although the combined stress inhibited seedling growth more than the single stress, the combined stress of MPs and NaCl showed antagonistic effects. These findings underscore the importance of assessing the ecological risks posed by the combined effects of MPs and salt stresses on maize plants.

Insight into the Amelioration Effect of Nitric Acid-Modified Biochar on Saline Soil Physicochemical Properties and Plant Growth

Soil salinization is a major factor threatening global food security. Soil improvement strategies are therefore of great importance in mitigating the adverse effect of salt stress. Our study aimed to evaluate the effect of biochar (BC) and nitric acid-modified biochar (HBC) (1%, 2%, and 3%; m/m) on the properties of salinized soils and the morphological and physiological characteristics of pakchoi. Compared with BC, HBC exhibited a lower pH and released more alkaline elements, reflected in reduced contents of K+, Ca2+, and Mg2+, while its hydrophilicity and polarity increased. Additionally, the microporous structure of HBC was altered, showing a rougher surface, larger pore size, pore volume, specific surface area, and carboxyl and aliphatic carbon content, along with lower aromatic carbon content and crystallinity. Moreover, HBC application abated the pH of saline soil. Both BC and HBC treatments decreased the sodium absorption rate (SAR) of saline soil as their concentration increased. Conversely, both types of biochar enhanced the cation exchange capacity (CEC), organic matter, alkali-hydrolyzable nitrogen, and available phosphorus and potassium content in saline soils, with HBC demonstrating a more potent improvement effect. Furthermore, biochar application promoted the growth-related parameters in pakchoi, and reduced proline and Na+ content, whilst increasing leaf K+ content under salt stress. Biochar also enhanced the activity of key antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)) in leaves, and reduced hydrogen peroxide (H2O2) and malondialdehyde (MDA) content. Collectively, modified biochar can enhance soil quality and promote plant growth in saline soils.

Simulation of red mud/phosphogypsum-based artificial soil engineering applications in vegetation restoration and ecological reconstruction

Red mud and phosphogypsum are two of the most typical bulk industrial solid wastes. How they can be efficiently recycled as resources on a large scale and at low costs has always been a global issue that urgently needs to be solved. By constructing a small-scale test site and preparing two types of artificial soils using red mud and phosphogypsum, this study simulated their engineering applications in vegetation restoration and ecological reconstruction. According to the results of this study, the artificial soils contained a series of major elements (e.g. O, Si, Al, Fe, Ca, Na, K, and Mg) similar to those in common natural soil, and preliminarily possessed basic physicochemical properties (pH, moisture, organic matter, and cation exchange capacity), main nutrient conditions (nitrogen, phosphorus and potassium), and biochemical characteristics that could meet the demands of plant growth. A total of 18 different types of adaptable plants (e.g. wood, herbs, flowers, succulents, etc) grew in the test sites, indicating that the artificial soils could be used for vegetation greening and landscaping. The preliminary formation of microbial (fungal and bacterial) community diversity and the gradually enriched arthropod community diversity reflected the constantly improving quality of the artificial soils, suggesting that they could be used for the gradual construction of artificial soil micro-ecosystems. Overall, the artificial soils provided a feasible solution for the large-scale, low-cost, and highly efficient synergistic disposal of red mud and phosphogypsum, with enormous potential for future engineering applications. They are expected to be used for vegetation greening, landscaping, and ecological environment improvement in tailings, collapse, and soil-deficient areas, as well as along municipal roads.

Pore Engineering in Biomass-Derived Carbon Materials for Enhanced Energy, Catalysis, and Environmental Applications

Biomass-derived carbon materials (BDCs) are highly regarded for their renewability, environmental friendliness, and broad potential for application. A significant advantage of these materials lies in the high degree of customization of their physical and chemical properties, especially in terms of pore structure. Pore engineering is a key strategy to enhance the performance of BDCs in critical areas, such as energy storage, catalysis, and environmental remediation. This review focuses on pore engineering, exploring the definition, classification, and adjustment techniques of pore structures, as well as how these factors affect the application performance of BDCs in energy, catalysis, and environmental remediation. Our aim is to provide a solid theoretical foundation and practical guidance for the pore engineering of BDCs to facilitate the rapid transition of these materials from the laboratory to industrial applications.

Maize, Peanut, and Millet Rotations Improve Crop Yields by Altering the Microbial Community and Chemistry of Sandy Saline-Alkaline Soils

Crop rotation increases crop yield, improves soil health, and reduces plant disease. However, few studies were conducted on the use of intensive cropping patterns to improve the microenvironment of saline soils. The present study thoroughly evaluated the impact of a three-year maize-peanut-millet crop rotation pattern on the crop yield. The rhizosphere soil of the crop was collected at maturity to assess the effects of crop rotation on the composition and function of microbial communities in different tillage layers (0-20 cm and 20-40 cm) of sandy saline-alkaline soils. After three years of crop rotation, the maize yield and economic benefits rose by an average of 32.07% and 22.25%, respectively, while output/input grew by 10.26%. The pH of the 0-40 cm tillage layer of saline-alkaline soils decreased by 2.36%, organic matter rose by 13.44%-15.84%, and soil-available nutrients of the 0-20 cm tillage layer increased by 11.94%-69.14%. As compared to continuous cropping, crop rotation boosted soil nitrogen and phosphorus metabolism capacity by 8.61%-88.65%. Enrichment of Actinobacteria and Basidiomycota increased crop yield. Crop rotation increases microbial community richness while decreasing diversity. The increase in abundance can diminish competitive relationships between species, boost synergistic capabilities, alter bacterial and fungal community structure, and enhance microbial community function, all of which elevate crop yields. The obtained insights can contribute to achieving optimal management of intensive cultivation patterns and green sustainable development.

Biological Nano-Agrochemicals for Crop Production as an Emerging Way to Address Heat and Associated Stresses

Climate change is a global problem facing all aspects of the agricultural sector. Heat stress due to increasing atmospheric temperature is one of the most common climate change impacts on agriculture. Heat stress has direct effects on crop production, along with indirect effects through associated problems such as drought, salinity, and pathogenic stresses. Approaches reported to be effective to mitigate heat stress include nano-management. Nano-agrochemicals such as nanofertilizers and nanopesticides are emerging approaches that have shown promise against heat stress, particularly biogenic nano-sources. Nanomaterials are favorable for crop production due to their low toxicity and eco-friendly action. This review focuses on the different stresses associated with heat stress and their impacts on crop production. Nano-management of crops under heat stress, including the application of biogenic nanofertilizers and nanopesticides, are discussed. The potential and limitations of these biogenic nano-agrochemicals are reviewed. Potential nanotoxicity problems need more investigation at the local, national, and global levels, as well as additional studies into biogenic nano-agrochemicals and their effects on soil, plant, and microbial properties and processes.

Relationships between Wheat Development, Soil Properties, and Rhizosphere Mycobiota

Wheat is a vital global food crop, yet it faces challenges in saline-alkali soils where Fusarium crown rot significantly impacts growth. Variations in wheat growth across regions are often attributed to uneven terrain. To explore these disparities, we examined well-growing and poorly growing wheat samples and their rhizosphere soils. Measurements included wheat height, root length, fresh weight, and Fusarium crown rot severity. Well-growing wheat exhibited greater height, root length, and fresh weight, with a lower Fusarium crown rot disease index compared to poorly growing wheat. Analysis of rhizosphere soil revealed higher alkalinity; lower nutrient levels; and elevated Na, K, and Ca levels in poorly growing wheat compared to well-growing wheat. High-throughput sequencing identified a higher proportion of unique operational taxonomic units (OTUs) in poorly growing wheat, suggesting selection for distinct fungal species under stress. FUNGuild analysis indicated a higher prevalence of pathogenic microbial communities in poorly growing wheat rhizosphere soil. This study underscores how uneven terrains in saline-alkali soils affect pH, nutrient dynamics, mineral content, wheat health, and rhizosphere fungal community structure.

Differential response of proline metabolism defense, Na+ absorption and deposition to salt stress in salt-tolerant and salt-sensitive rapeseed (Brassica napus L.) genotypes

Soil salinization is a major abiotic factor threatening rapeseed yields and quality worldwide, yet the adaptive mechanisms underlying salt resistance in rapeseed are not clear. Therefore, this study aimed to explore the differences in growth potential, sodium (Na+) retention in different plant tissues, and transport patterns between salt-tolerant (HY9) and salt-sensitive (XY15) rapeseed genotypes, which cultivated in Hoagland's nutrient solution in either the with or without of 150 mM NaCl stress. The results showed that the inhibition of growth-related parameters of the XY15 genotype was higher than those of the HY9 in response to salt stress. The XY15 had lower photosynthesis, chloroplast disintegration, and pigment content but higher oxidative damage than the HY9. Under NaCl treatment, the proline content in the root of HY9 variety increased by 8.47-fold, surpassing XY15 (5.41-fold). Under salt stress, the HY9 maintained lower Na+ content, while higher K+ content and exhibited a relatively abundant K+/Na+ ratio in root and leaf. HY9 also had lower Na+ absorption, Na+ concentration in xylem sap, and Na+ transfer factor than XY15. Moreover, more Na+ contents were accumulated in the root cell wall of HY9 with higher pectin content and pectin methylesterase (PME) activity than XY15. Collectively, our results showed that salt-tolerant varieties absorbed lower Na+ and retained more Na+ in the root cell wall (carboxyl group in pectin) to avoid leaf salt toxicity and induced higher proline accumulation as a defense and antioxidant system, resulting in higher resistance to salt stress, which provides the theoretical basis for screening salt resistant cultivars.

Effects of Biochar and Straw Amendment on Soil Fertility and Microbial Communities in Paddy Soils

Straw and biochar, two commonly used soil amendments, have been shown to enhance soil fertility and the composition of microbial communities. To compare the effects of straw and biochar on soil fertility, particularly focusing on soil dissolved organic matter (DOM) components, and the physiochemical properties of soil and microbial communities, a combination of high-throughput sequencing and three-dimensional fluorescence mapping technology was employed. In our study, we set up four treatments, i.e., without biochar and straw (B0S0); biochar only (B1S0); straw returning only (B0S1); and biochar and straw (B1S1). Our results demonstrate that soil organic matter (SOM), available nitrogen (AN), and available potassium (AK) were increased by 34.71%, 22.96%, and 61.68%, respectively, under the B1S1 treatment compared to the B0S0 treatment. In addition, microbial carbon (MBC), dissolved organic carbon (DOC), and particulate organic carbon (POC) were significantly increased with the B1S1 treatment, by 55.13%, 15.59%, and 125.46%, respectively. The results also show an enhancement in microbial diversity, the composition of microbial communities, and the degree of soil humification with the application of biochar and straw. Moreover, by comparing the differences in soil fertility, DOM components, and other indicators under different treatments, the combined treatments of biochar and straw had a more significant positive impact on paddy soil fertility compared to biochar. In conclusion, our study revealed the combination of straw incorporation and biochar application has significant impacts and is considered an effective approach to improving soil fertility.

Biochar and hydrochar application influence soil ammonia volatilization and the dissolved organic matter in salt-affected soils

Biochar, which including pyrochar (PBC) and hydrochar (HBC), has been tested as a soil enhancer to improve saline soils. However, the effects of PBC and HBC application on ammonia (NH3) volatilization and dissolved organic matter (DOM) in saline paddy soils are poorly understood. In this research, marsh moss-derived PBC and HBC biochar types were applied to paddy saline soils at 0.5 % (w/w) and 1.5 % (w/w) rates to assess their impact on soil NH3 volatilization and DOM using a soil column experiment. The results revealed that soil NH3 volatilization significantly increased by 56.1 % in the treatment with 1.5 % (w/w) HBC compared to the control without PBC or HBC. Conversely, PBC and the lower application rate of HBC led to decrease in NH3 volatilization ranging from 2.4 % to 12.1 %. Floodwater EC is a dominant factor in NH3 emission. Furthermore, the fluorescence intensities of the four fractions (all humic substances) were found to be significantly higher in the 1.5 % (w/w) HBC treatment applied compared to the other treatments, as indicated by parallel factor analysis modeling. This study highlights the potential for soil NH3 losses and DOM leaching in saline paddy soils due to the high application rate of HBC. These findings offer valuable insights into the effects of PBC and HBC on rice paddy saline soil ecosystems.

Alleviation of cotton growth suppression caused by salinity through biochar is strongly linked to the microbial metabolic potential in saline-alkali soil

Biochar is a typical soil organic amendment; however, there is limited understanding of its impact on the metabolic characteristics of microorganisms in saline-alkaline soil microenvironment, as well as the advantages and disadvantages of plant-microorganism interactions. To elucidate the mechanisms underlying the impact of saline-alkali stress on cotton, a 6-month pot experiment was conducted, involving the sowing of cotton seedlings in saline-alkali soil. Three different biochar application levels were established: 0 % (C0), 1 % (C1), and 2 % (C2). Results indicated that biochar addition improved the biomass of cotton plants, especially under C2 treatment; the dry weight of cotton bolls were 8.15 times that of C0. Biochar application led to a rise in the accumulation of photosynthetic pigments by 8.30-51.89 % and carbohydrates by 7.4-10.7 times, respectively. Moreover, peroxidase (POD) activity, the content of glutathione (GSH), and ascorbic acid (ASA) were elevated by 23.97 %, 118.39 %, and 48.30 % under C2 treatment, respectively. Biochar caused a reduction in Na+ uptake by 8.21-39.47 %, relative electrical conductivity (REC) of plants, and improved K+/Na+ and Ca2+/Na+ ratio indicating that biochar alleviated salinity-caused growth reduction. Additionally, the application of biochar enhanced the absorption intensity of polysaccharide fingerprints in cotton leaves and roots. Two-factor co-occurrence analysis indicated that the key differential metabolites connected to several metabolic pathways were L-phenylalanine, piperidine, L-tryptophan, and allysine. Interestingly, biochar altered the metabolic characteristics of saline-alkali soil, especially related to the biosynthesis and metabolism of amino acids and purine metabolism. In conclusion, this study demonstrates that biochar may be advantageous in saline soil microenvironment; it has a favorable impact on how plants and soil microbial metabolism interact.