Search Results (2,510)

The excessive use of chemical fertilizers raised concerns regarding environmental sustainability and soil degradation, prompting increasing interest in biofertilizers as eco-friendly alternatives. Among these, a compound that is effective in stimulating root and plant growth is indole-3-acetic acid (IAA). In our study, we evaluated IAA production by the halotolerant bacterium Vreelandella titanicae under different and varying nutritional conditions, such as tryptophan availability, temperature, pH, salinity, etc. The bacterium showed significant IAA production under a broad range of conditions and a dependence on the presence of tryptophan for IAA biosynthesis. High salinity (1.0 M NaCl), slightly alkaline pH (8.0–9.0), and temperatures of 34 °C increased IAA production, while optimal growth occurred in the absence of NaCl at a range of temperatures of 25–28 °C, suggesting a stress-responsive regulation of its biosynthesis. Easily metabolizable carbon sources, such as glucose and mannitol, enhanced IAA yield again, whereas additions of 1.0 g L⁻¹ NH₄NO₃ and KH₂PO₄ in the basal medium, poor in these salts, inhibited both the growth of the bacterium and IAA production. Notably, V. titanicae produced relevant amounts of IAA in seawater (24.57 ± 11.28 μg⋅mL⁻¹) when used as growth medium and dairy whey (15.68 ± 2.42 μg⋅mL⁻¹), highlighting its suitability for low-cost and circular bioprocessing strategies. In conclusion, V. titanicae is a promising Plant Growth-Promoting Rhizobacterium (PGPR) candidate for sustainable IAA production and potential application in saline or marginal agricultural soils. Its ability to synthesize IAA in different growth media could allow its exploitation in environmentally friendly bioprocesses. Full article

Understanding the distribution of water and salt in the crop’s root zone and predicting future soil degradation requires specific monitoring to establish guidelines for irrigation management and system performance. Two field experiments were conducted in the arid region of Southern Tunisia to assess soil water and salt dynamics under surface- and drip-irrigated carrots using HYDRUS 2D/3D simulations in the 2017–2018 and 2018–2019 crop seasons. The soil water contents and bulk soil electrical conductivities were measured at three distinct soil layers: 0–20 cm, 20–40 cm, and 40–60 cm, where TDR probes were located. Statistical indicators (nRMSE, IA, and PBIAS) suggest that HYDRUS 2D/3D is reliable in simulating field hydro-saline dynamics for irrigated carrots. The results obtained for the two crop seasons exhibit a strong correlation between the simulated and measured values for both soil water contents and electrical conductivities. The study also shows that HYDRUS 2D/3D allows more accurate simulations of soil water dynamics than soil salinity under these conditions. Overall, these results provide valuable insights for understanding the hydrological processes in arid regions and can help in improving the management of water resources in these areas. Full article

Soil corrosion is a critical durability and cost factor for metallic foundations in photovoltaic (PV) power plants, yet it is still addressed with fragmented criteria compared with atmospheric corrosion. This paper reviews the main soil corrosivity drivers relevant to PV installations—moisture and aeration dynamics, electrical resistivity, pH and buffer capacity, dissolved ions (notably chlorides and sulfates), microbiological activity, hydro-climatic variability and geological heterogeneity—highlighting their coupled and non-linear effects, such as differential aeration, macrocell formation and corrosion localization. Building on this mechanistic basis, an engineering-oriented methodological roadmap is proposed to translate soil characterization into durability decisions. The approach combines soil corrosivity classification according to DIN 50929-3 and DVGW GW 9, tiered estimation of hot-dip galvanized coating consumption using AASHTO screening, resistivity–pH correlations and ionic penalty factors, and verification against conservative NBS envelopes. When coating life is insufficient, a traceable steel thickness allowance based on DIN bare-steel corrosion rates is introduced to meet the target service life. The framework provides a practical and auditable basis for durability design and risk control of PV foundations in heterogeneous soils. The proposed framework shows that, for soils exceeding AASHTO mild criteria, zinc corrosion rates may increase by a factor of 1.3–1.7 when chloride and sulfate penalties are considered, potentially reducing coating service life by more than 40%. The methodology proposed enables designers to estimate the penalty factors for sulfates ($f_p\left({SO}_4^{2-}\right)$) and chlorides ($f_p\left({Cl}^{-}\right)$) in each specific project, calculating the appropriate values of $K_{{SO}_4^{2-}}$ and $K_{{Cl}^{-}}$ using electrochemical techniques—ER/LPR and EIS—to estimate the effect of the soluble salts content in the ${Zn}_{Corr Rate}$, not properly catch by the proxy indicator $V_{corr}\left(ER, pH\right)$ when sulfate and chloride content are over AAHSTO limits for mildly corrosive soils. Full article

Soil salinity is recognized as a critical abiotic stress that limits plant growth on marginal lands. The cup plant (Silphium perfoliatum L.), a perennial bioenergy species with high biomass potential, has been proposed for cultivation on saline-degraded soils; however, its physiological responses to different types of salinity stress, particularly alkaline and neutral salt stress, remain insufficiently characterized. In the present study, the physiological responses of the cup plant to neutral (NaCl) and alkaline (NaHCO₃) salt stress at concentrations of 100, 200, and 300 mM were evaluated in a pot experiment conducted under controlled conditions. The assessed indicators included relative chlorophyll content (CCI), chlorophyll fluorescence parameters (F_v/F_m, F_v/F₀, PI), and gas exchange characteristics, namely net photosynthetic rate (P_N), stomatal conductance (g_s), transpiration rate (E), and intercellular CO₂ concentration (C_i). Salinity reduced most physiological parameters, although some, such as maximum photochemical efficiency of PSII (F_v/F_m) and transpiration rate (E), did not show a clear dose-dependent response. Alkaline salt stress induced more pronounced reductions in the physiological parameters than neutral salt stress. At the first measurement, at the highest salt concentration, the chlorophyll content decreased by 49.0% and the P_N parameter by 77.8% under NaHCO₃ treatment, whereas under NaCl conditions the decreases were 29.0% and 51.3%, respectively, compared to the control. At 300 mM NaHCO₃, the chlorophyll content and photosynthetic rate were substantially reduced compared with those recorded under the corresponding NaCl treatment. Even at the moderate salinity level of 100 mM NaHCO₃, reductions in photosynthetic performance were detected relative to the control. Overall, photosynthetic efficiency and gas exchange in the cup plant were markedly impaired by salinity, particularly under conditions of high bicarbonate concentration. The results offer a deeper understanding of the physiological limitations of S. perfoliatum under acute salt stress and demonstrate that alkaline salinity, associated with elevated pH due to HCO₃⁻, exacerbates stress effects beyond the osmotic and ionic impacts of neutral salinity. These results highlight the potential of S. perfoliatum for sustainable biomass production on salt-affected soils, supporting renewable energy generation and environmentally responsible land use. Full article

In severely saline-alkali soils, surface salt accumulation caused by intense water evaporation results in elevated salinity, low organic matter content, and suppressed microbial activity, collectively impairing plant physiological metabolism and growth. Superabsorbent polymers hold significant potential for ameliorating saline-alkali soils by regulating soil water–salt dynamics. Biochar, a carbon-rich organic material, plays a pivotal role in enhancing soil organic matter storage, whereas vermicompost, a microbiologically active organic amendment, contributes substantially to improving soil microbial functions. Therefore, this study developed a novel superabsorbent polymer reinforced with vermicompost and biochar (VB-SAP) and further investigated its effects on metabolic pathways associated with enhanced S. cannabina stress resistance in severely saline-alkali soils. The results showed that VB-SAPs significantly increased soil water and organic matter contents by 10.9% and 38.7% (p < 0.05), respectively, and decreased topsoil salinity of saline soils by 44.9% (p < 0.05). The application of VB-SAP altered the soil bacterial community structure and increased the complexity of the bacterial co-occurrence network, specifically enriching members of the phylum Pseudomonadota, which are widely recognized as common plant growth-promoting rhizobacteria. Moreover, VB-SAPs significantly upregulated root-associated salt tolerance genes involved in phenylpropanoid biosynthesis, tryptophan metabolism, and arginine–proline pathways, thereby enhancing root biomass accumulation, nutrient uptake, and shoot growth of S. cannabina. Collectively, these findings reveal that the new type of superabsorbent polymer reinforced with vermicompost and biochar may enhance the salt tolerance and growth of S. cannabina by reshaping the rhizosphere microenvironment, including reducing soil salinity, increasing soil water and organic matter contents, and promoting beneficial bacteria in severely saline-alkali soil, thereby providing novel strategies for the integrated improvement of saline soils. Full article

In coastal saline soil regions, foundation instability frequently arises due to salt heave, dissolution-induced weakening and corrosion-driven degradation. To enhance the engineering performance of fine-grained saline soil, this study evaluates the effectiveness of Enzyme-Induced Carbonate Precipitation (EICP) treatment under varying salinity levels and curing solution concentrations. Mechanical properties, hydraulic behavior and water stability were examined through unconfined compressive strength (UCS), disintegration and permeability tests, complemented by microstructural analyses using XRD and SEM. The results indicate that EICP notably improves mechanical strength, water stability and reduced permeability. The UCS of treated specimens increased by 37–152% relative to untreated soil, and disintegration time was prolonged by 214–563%. The permeability coefficient was reduced by 45.8–95.7%, demonstrating effective suppression of seepage channels. The optimal stabilization performance was achieved at 0.02% salinity and curing concentrations of 1.0–1.3×. Excessive salinity distorted vaterite crystal morphology and weakened cementation. XRD and SEM analyses revealed that vaterite dominated the calcium carbonate polymorphs, while ionic complexity influenced crystal structure, ACC conversion and pore-filling performance. These findings confirm the feasibility of applying EICP for improving fine-grained coastal saline soils and provide practical engineering guidance for coastal subgrades, reclamation foundations and port infrastructures. Full article

Drip irrigation burial depth is a critical management factor for saline-alkali agriculture, yet its mechanisms of influencing crop productivity through soil–microbe–plant interactions remain poorly understood. To explore the regulatory effects of drip irrigation burial depth on the growth and rhizosphere microenvironment of dryland wheat in saline-alkali soil, three treatments (no irrigation control, CK; 5 cm shallow-buried drip irrigation, T5; 25 cm deep-buried drip irrigation, T25) were set up, with soil physicochemical properties, microbial community characteristics, and crop yield analyzed. The results showed that drip irrigation significantly improved soil environment and yield, and T25 exhibited superior comprehensive benefits: soil electrical conductivity was reduced by 63%, organic matter content increased by 44%, and water-salt status was significantly optimized; meanwhile, microbial community structure was altered and root nutrient uptake capacity was enhanced, ultimately achieving a yield of 5347.1 kg ha⁻¹, 55.0% higher than CK. In conclusion, 25 cm deep-buried drip irrigation may provide advantages for wheat cultivation primarily through improved water distribution, desalination, and soil structure enhancement. Full article

A novel bacterial strain, designated as 4-30^T, was isolated from a soil sample collected from the Kubuqi Desert in Inner Mongolia, northern China. The isolate was a Gram-stain-positive, aerobic, motile, and coccus-shaped bacterium, and its colonies were circular, opaque, convex, smooth, and orange-pigmented on Luria–Bertani agar. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain 4-30^T belonged to the genus Planococcus. Growth occurred at 4–38 °C (optimum, 25–28 °C), pH 6.0–11.0 (optimum, pH 9.0), and in 0–10% (w/v) NaCl (optimum, 1%). Strain 4-30^T contained iso-C_14:0, anteiso-C_15:0, C_16:1 ω7c alcohol, and iso-C_16:0 as major cellular fatty acids (>10%) and MK-7 and MK-8 as predominant menaquinones. Its polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and two unidentified polar lipids. The genomic DNA G+C content was 45.9%. The average nucleotide identity (ANI) values between strain 4-30^T and the closely related species were relatively low (ANIm < 85.6%, ANIb < 82.9% and OrthoANIu < 83.3%), and the digital DNA–DNA hybridization (dDDH) between strain 4-30^T and type strains of the genus Planococcus were 20.0–26.7%. Based on phylogenetic, genotypic, chemotaxonomic, and phenotypic analyses, strain 4-30^T is considered to represent a novel species of the genus Planococcus, for which the name Planococcus circulans sp. nov. is proposed. The type strain is 4-30^T (=CDMCC 1.2409^T = KCTC 43405^T). Full article

Plant organic cation transporters (OCTs) are involved in a variety of beneficial biological processes, such as cadaverine transfer in plants and soil, and play an active role in the formation of plant stress resistance. In this study, 52 OCT family genes were identified in tomato, and comprehensive bioinformatics analyses of these numbers, such as promoter cis-acting elements, gene mapping and collinearity, protein characterization and phylogenetic analysis. By analyzing the expression of tomato OCT family genes under cold and salt stresses using transcriptome data and qRT-PCR experiments, a key gene regulating cold stress tolerance, SlOCT20, was identified. Subcellular localization experiments indicated that SlOCT20 was mainly localized in the cell membrane. When the SlOCT20 gene was silenced in tomato, the tolerance to cold stress was significantly reduced and oxidative stress was aggravated, indicating that this gene positively regulates the tolerance to cold stress in tomato. Full article

Soil salinity is a major constraint to wheat production worldwide. Efficient screening of salt-tolerant cultivars is essential for breeding programs, yet a rapid and reliable evaluation system based on full-life-cycle salt stress treatment is lacking. To address this, we conducted a hydroponic experiment encompassing the entire growth cycle of 37 wheat cultivars under control and salt stress (85.5 mM NaCl). Using principal component and stepwise regression analyses on 15 agronomic and yield-related traits, we identified five key indicators—total dry weight, root dry weight, plant height, thousand-grain weight, and number of grains per spike—that effectively represent overall salt tolerance. Based on a comprehensive evaluation value (D-value), the cultivars were classified into five distinct categories: highly salt-tolerant, salt-tolerant, moderately salt-tolerant, weakly salt-tolerant, and salt-sensitive. Notably, the highly salt-tolerant cultivar ‘Yangfumai 8′ and the salt-sensitive cultivar ‘Yangmai 22’ were selected as representative extremes. A subsequent pot experiment confirmed significant physiological differences between them in antioxidant enzyme activities (SOD, POD, CAT) and proline accumulation under salt stress. This study establishes a practical and efficient screening framework, providing breeders with a simplified index set for high-throughput evaluation and offering ideal contrasting materials for in-depth physiological research on salt tolerance mechanisms in wheat. Full article

Salinization is a growing global problem, particularly in arid and semi-arid areas, where salt concentration interferes with the soil structure, altering natural cycling, decreasing agricultural outputs, and threatening food security. Although many soil amendments have been studied, there is still a limited understanding of their interaction with soil after mixture application and the geochemical processes and long-term sustainability that govern their effects. To address this knowledge gap, this review elucidated the effectiveness and sustainability of soil amendments, biochar, humic substances, and mineral additives in restoring saline and sodic soils of arid and semi-arid region to explore the geochemical processes that underlie their impact. A systematic search of 174 peer-reviewed studies was conducted across multiple databases (Web of Science, Google Scholar, and Scopus) using relevant keywords and the findings were converted into quantitative values to evaluate the effects of biochar, gypsum, zeolite, and humic substances on key soil properties. Biochar significantly improved cation exchange capacity, nutrient retention, microbial activity, and water retention by enhancing soil porosity and capillarity, thereby increasing plant-available water. Gypsum improved phosphorus availability, while zeolite facilitated the removal of sodium and supported microbial activity. Humic substances enhanced soil porosity, water retention, and aggregate stability. When applied together, these amendments improved soil health by regulating salinity, enhancing nutrient cycling, while also stabilizing soil conditions and ensuring long-term sustainability through improved geochemical balance and reduced environmental impacts. The findings highlight the critical role of multi-functional amendments in promoting climate-resilient agriculture and long-term soil health restoration in saline-degraded regions. Further research and field implementation are crucial to optimize their effectiveness and ensure sustainable soil management across diverse agricultural environments. Full article

The high salt content in saline–alkali soil has a significant impact on plant nutrient absorption and water transport, severely inhibiting crop growth. Through esterification reactions, silicic acid is grafted onto humic acid to form an organic silicon fertilizer (OSiF). The unique Si-O-C bond in the material endows this new type of organic silicon-based fertilizer with the ability to effectively alleviate the harm of high-salt soil to plants. In this study, a soil column experiment was designed to systematically evaluate and compare the effects of organic silicon fertilizers with different organic silicon contents (0%, 5%, and 10%) and traditional compound fertilizers on soil water characteristics, salt ion concentration, pH value, and electrical conductivity. The results showed that the addition of an appropriate amount of organic silicon fertilizer could significantly reduce the activity of salt ions in the soil solution. Experimental data indicated that the 5% and 10% organic silicon fertilizers had the most significant effect on the consumption of major salt ions such as sodium and chloride ions. X-ray photoelectron spectroscopy (XPS) analysis revealed that the reaction of Si-O-C bonds in the soil with Lewis bases led to a shift in the valence state of the 1S electrons of silicon atoms, providing a theoretical basis for the mechanism by which silicon fertilizers alleviate high-salt stress. Full article

This study investigates the effects of saline reclaimed water recharge on soil salt accumulation and water migration in Xinjiang, China, aiming to provide scientific guidance for the sustainable utilization of reclaimed water in arid regions. Indoor vertical infiltration simulation experiments were conducted using reclaimed water with varying salinity levels (0, 1, 2, 3, and 4 g L⁻¹) to evaluate their impacts on soil water–salt distribution and infiltration dynamics. Results showed that irrigation with saline reclaimed water increased soil pH and significantly enhanced both the infiltration rate and wetting front migration velocity, while causing only minor changes in the moisture content of the wetted zone. When the salinity was 2 g L⁻¹, the observed improvement effect was the most significant. Specifically, the cumulative infiltration increased by 22.73% after 180 min, and the time required for the wetting peak to reach the specified depth was shortened by 21.74%. At this salinity level, the soil’s effective water storage capacity reached 168.19 mm, with an average moisture content increase of just 6.20%. Soil salinity increased with the salinity of the irrigation water, and salts accumulated at the wetting front as water moved downward, resulting in a characteristic distribution pattern of desalination in the upper layer and salt accumulation in the lower layer. Notably, reclaimed water recharge reduced soil salinity in the 0–30 cm layer, with salinity in the 0–25 cm layer decreasing below the crop salt tolerance threshold. When the salinity of the reclaimed water was ≤2 g L⁻¹, the salt storage in the 0–30 cm layer was less than 7 kg ha⁻¹, achieving a desalination rate exceeding 60%. Reclaimed water with a salinity of 2 g L⁻¹ enhanced infiltration (wetting front depth increased by 27.78%) and desalination efficiency (>60%). These findings suggest it is well suited for urban greening and represents an optimal choice for the moderate reclamation of saline-alkali soils in arid environments. Overall, this study provide a reference for the water quality threshold and parameters of reclaimed water for urban greening, farmland irrigation, and saline land improvement. Full article

Recently, the EU approved RENURE-criteria materials to be used as substitutes for synthetic N fertilisers. Several studies have been performed on the agronomic efficacy and potential environmental impacts of different bio-based fertilisers (BBFs) from biomass recovery, including the RENURE-criteria materials. But information is lacking about their effectiveness under abiotic stress conditions like salinity and drought. The predictions for climate change-induced increased drought and soil salinisation for the European soils have also increased, making it inevitable to understand BBF performance in these impending situations. Two RENURE-criteria top-priority materials (ammonium nitrate (AN) and ammonium sulphate (AS) and another commercially used BBF—an evaporator concentrate (CaE)) were evaluated in a pot trial growing spinach under salinity and drought stress with a reference ‘no stress’ condition to examine crop growth, nutrient uptake, and nitrogen fertiliser replacement value (NFRV). Agronomically, BBFs performed at par with the synthetic fertiliser (SF) under unstressed and salt-stressed conditions, whereas, under drought stress, BBFs outperformed the SF treatment. AS exhibited the highest yield and nutrient uptake, displaying an NFRV of 3.1 and 1.8 under no-stress and salt-stress conditions, respectively. Salt stress did not negatively impact the crops grown in this trial, potentially due to the higher potassium content in the system, which alleviated the possible negative impacts of high sodium. This study delves into the agronomic response, without evaluating crop physiological changes, and, hence, should be taken as a preliminary step into further investigation of observed elemental interactions (that could be potentially driving stress mitigation) while also examining the crop physiology during the duration of stress. Full article

The imbalance between water supply and demand in the arid and semi-arid regions of northwest China has become increasingly severe, highlighting the urgent need to develop and utilize unconventional water resources. Return flow, originating from canal leakage and field drainage, is widely distributed in these regions. However, as it contains a certain amount of salts, long-term use of return flow can lead to soil salinization and degradation of soil structure. Therefore, the scientific utilization of return flow has become a key issue for achieving sustainable agricultural development and efficient water use in arid areas. This study was conducted in the Yinbei Irrigation District, Ningxia, northwest China. Water samples were collected from the main and branch drainage ditches and analyzed to evaluate the feasibility of using return flow irrigation in the area. In addition, based on two years of continuous field monitoring and HYDRUS model simulations, the long-term dynamics of soil salinity under moderate return flow irrigation over the next 20 years were predicted. The results show that the total salinity of the main return ditches consistently remained below the agricultural irrigation water quality standard of 2000 mg/L, with Na⁺ and SO₄²⁻ as the predominant ions. Seasonal variations in return flow salinity were notable, with higher levels observed in spring compared to summer. Simulation results based on field trial data indicated that soil salinity displayed regular seasonal fluctuations. During the rice-growing season, strong leaching kept the salinity in the plough layer (0–40 cm) low. However, after irrigation ceased, evaporation in autumn and winter led to an increase in surface soil salinity, creating annual peaks. Long-term simulations showed that soil salinity throughout the entire profile (0–100 cm) followed a pattern of “slight increase—gradual decrease—dynamic stability.” Specifically, winter salinity peaks slightly increased during the first two years but then gradually declined, stabilizing after approximately 15 years. This indicates that long-term return-flow irrigation does not result in the accumulation of soil salinity in the plough layer. Full article