Search Results (40)

Alkaline stress (AS) is one of the major threats that severely affects rice growth and grain yield. However, the differences in the damage caused by the main components of soda saline-alkali land, sodium carbonate (Na₂CO₃), and sodium bicarbonate (NaHCO₃) to rice seedlings are still unclear. This study explored the effects of different carbonate stresses (Na₂CO₃ and NaHCO₃) on rice seedling growth, root damage, physiological responses, and molecular changes. By administering equivalent concentrations of sodium ions through these different carbonate treatments, we observed that both stresses significantly inhibited rice growth. However, the inhibitory effect was more pronounced under the Na₂CO₃ treatment. Compared with the NaHCO₃ treatment, Na₂CO₃ stress caused more severe damage to root cell membranes and led to a substantial decline in root vigor. Moreover, the contents of reactive oxygen species (ROS) and malondialdehyde (MDA) were markedly increased, indicating that Na₂CO₃ induces more severe oxidative damage. Transcriptomic and metabolomic analyses revealed a greater number of differentially expressed genes (DEGs) and differentially expressed metabolites (DEMs) in the Na₂CO₃ treatment group. The integrative analysis and validation demonstrated that pathways related to auxin, ascorbate, flavonoids, and glutathione metabolism were particularly enriched under Na₂CO₃ stress. These findings suggest that Na₂CO₃ stress may interfere with auxin signaling pathways and exerts a more profound impact on endogenous antioxidant systems, affecting rice growth at multiple levels. In summary, this research highlights the differential impacts of Na₂CO₃ and Na₂CO₃ stresses on rice seedling growth, physiology, and molecular processes, particularly oxidative damage and antioxidant responses. The insights gained provide a valuable theoretical foundation for enhancing rice alkali tolerance and developing strategies for the rational cultivation of rice in saline-alkaline soils. Full article

High pH, ${\mathrm{Na}}^{+}$, and $({\mathrm{CO}}_3^{2-}+{\mathrm{HCO}}_3^{-}$) are the primary characteristics of soda saline–alkali soil. Current strategies for ameliorating soda saline–alkali soil often involve the combined use of cow manure and maize straw, the addition of biochar (BC), and the inoculation of Bacillus subtilis (BS). In this study, B. subtilis-loaded biochar (BSC) was prepared using an adsorption technique. An incubation experiment was conducted. The treatments were as follows: soda saline–alkali soil amended with maize straw and cow manure (T₁), which was used as a control; T₁ supplemented with earthworms (T₂); and T₂ supplemented with BS (T₃), BC (T₄), or BSC (T₅). After a 60-day incubation, T₅ showed the most significant reduction in pH, ESP, and (${\mathrm{H}\mathrm{C}\mathrm{O}}_3^{-}$ + ${\mathrm{C}\mathrm{O}}_3^{2-}$) concentrations, with reductions of 0.24 units, 3.26%, and 120 mg kg⁻¹, respectively, compared to the T₁ treatment. The content of soil humic acid, available potassium, and available nitrogen and the activities of β-glucosidase and urease were highest in T₅, increasing by 33.5%, 70.1%, 26.1%, 19.0%, and 17.9%, respectively. Microbial sequencing analysis revealed that the Bacillus abundance in T₃ was highest during the first 45 days (2.51–3.65%), while the Bacillus abundance in T₅ peaked at 3.22% after the 60-day incubation. The soil that was cultivated for 60 days in the experiments was then used for planting alfalfa. T₅ showed the highest alfalfa aboveground biomass and peroxidase, increasing by 30.1% and 73.1%, respectively, compared with T₁. This study demonstrated that loading onto biochar is beneficial for the survival of B. subtilis in soda saline–alkali soil. When traditional organic materials are used, the combination of earthworms and B. subtilis-loaded biochar significantly alleviates the constraints of soda saline–alkali soil. Full article

Soil salinization is closely related to land degradation and is presumed to exert a significant effect on the preservation of soil organic carbon (SOC). However, the salinization-induced changes in SOC accumulation over the application gradient of amendments remain unclear. To evaluate the potential for salinization elimination and C sequestration, incubation experiments with four straw addition levels and six aluminum sulfate (Al³⁺) gradients were conducted in a soda saline–alkali soil, followed by the analysis of partial least squares path models (PLS-PM). The results showed that combined applications significantly reduced soil salinity and sodicity. The C sequestration performance under coapplications was greater than that under individual applications. The SOC and heavy fraction OC (HFOC) contents under the coapplication of 1.6% Al³⁺ and 10% straw were greater than those under the individual applications of either 1.6% Al³⁺ or 10% straw by 231.08% and 149.86%, and 9.70% and 18.78%, respectively. Coapplications significantly increased macroaggregates and aggregate-associated SOC levels. PLS-PM demonstrated that Na⁺, Ca²⁺ and HCO₃⁻ were important environmental factors associated with C sequestration. Overall, our results suggest that Al³⁺ and straw enhanced C sequestration by regulating salt ions and increasing soil aggregates and that 10% straw combined with 1.6% Al³⁺ had a greater effect on soda saline–alkali soil. Our study is highly important for the utilization of saline–alkali land and C sequestration in western Jilin Province. Full article

Rice serves as the staple food for half of the world’s population. Given the expanding global population, the urgency to allocate land for rice cultivation is paramount. In Northeast China, saline–sodic and black soils represent two distinct soil types used in rice production. During rice growth, soil microorganisms, including arbuscular mycorrhizal fungi (AMF), play pivotal roles in nutrient uptake and resistance to biotic and abiotic stressors. While numerous studies have elucidated the role of AMF in enhancing rice growth and its adaptation to stress, the differences in AMF communities within paddy fields between different soil types have been largely overlooked. In this study, high-throughput sequencing technology was employed to analyze the diversity and community structure of AMF, and metagenomic sequencing was employed to analyze AMF functional gene differences between the two soil types (black and saline–sodic soils). At the same time, the commonalities and differences of the soil characteristics (nitrogen, phosphorus, potassium, pH, etc.) were verified in influencing AMF communities. The results indicated that Glomus was the predominant genus in both soil types, followed by Paraglomus. The overall abundance of AMF was higher at the heading stage than at the harvest stage, with Paraglomus showing greater adaptation to the saline–sodic soil environment. Total phosphorus (TP) was identified as the primary factor influencing AMF diversity at the heading stage. In the harvest stage, AMF community diversity was greater in saline–sodic paddy soil compared to black soil, a reversal from the heading stage. Further analysis of the functional genes of Rhizophagus intraradices revealed that gene activity in the heading stage of saline soils significantly surpassed that in black soils, suggesting that R. intraradices plays a more crucial role in saline environments. Additionally, spore density and the content of easily extractable glomalin-related soil protein were relatively higher in saline–sodic soil than in black soil. Thus, it may be inferred that AMFs are more vital in saline–sodic soils than in black soils of the paddy fields in Northeast China. This study may offer valuable insights into the utilization of AMF in paddy fields in Northeast China. Full article

In western Jilin Province, China, the presence of soda saline–alkali soil poses a significant threat to the raising of rice seedlings due to its harsh soil properties. The scarcity of suitable seedling-raising soil resources has become increasingly pronounced. A short-term soil-improvement experiment was conducted using the original saline–alkali soil sourced from the rice-growing region of Jilin Province, followed by the rice-seedling-raising test in the improved soil to identify an effective soil-improvement strategy. Four distinct treatments were established: no amendment (JCK); gypsum and straw (JCW); gypsum, straw, and sulfuric acid (JCWH); and gypsum, straw, and chemical fertilizer (JCWF). The effects of these amendment treatments on the soil physicochemical properties (pH, electrical conductivity, exchangeable sodium, total alkalinity) were evaluated, as well as the effects on soil organic carbon (SOC) and its components including humic acid carbon (HAC), and fulvic acid carbon (FAC). The results indicated that, compared to the control group, all amendment treatments effectively reduced the average soil pH by 0.53 to 0.79 units and decreased exchangeable sodium by 56.7% to 74.8%. Furthermore, the average SOC, HAC, and FAC increased by 48.3%, 89.4%, and 56.0%, respectively. Among the treatments, JCWH proved to be the most effective. After two years of improvement, the rice seedlings in the JCWH-treated soil exhibited the highest dry weight and plant height, surpassing those grown in the farmer’s seedling-raising soil. The scheme of utilizing soda saline–alkali soil for rice-seedling raising, following a short-term improvement treatment with corn straw, gypsum, and sulfuric acid (JCWH), provides technical support and an effective solution to the soil scarcity issue faced by seedling farmers in saline–alkali regions. Full article

The implementation of scientific cultivation practices on soda saline–alkali land plays a pivotal role in safeguarding food security and promoting sustainable agro-economic development at the regional scale. However, there exists a critical knowledge gap regarding the optimization of tillage strategies for rain-fed maize (Zea mays L.) cultivation across heterogeneous saline–alkali soil matrices. This study selected meadow alkaline soil, saline meadow soil, and mild saline–alkali soil under the typical micro-landscape morphological characteristics of soda saline–alkali soil in the Songnen Plain as experimental plots. Under three tillage methods, namely no tillage (NT), rotary tillage + no tillage (RT), and subsoiling + rotary tillage + no tillage (SRT), the effects of the tillage methods on the soil physical properties at the seedling stage, root development at the V6 stage, and yield at the R6 stage during the process of cultivating maize in different types of soils were analyzed. The research results showed that compared with NT and RT, the SRT treatment better improved the physical properties, such as penetration resistance and the bulk density in micro-spaces (0–40 cm), of different soil types. The SRT treatment had a positive impact on the root development of maize seedlings in saline meadow soil and meadow alkaline soil. In terms of yield, compared with the NT treatment, the SRT treatment in meadow alkaline soil and saline meadow soil had a positive effect on the plant height, root dry weight, 1000–grain weight, and grain yield of maize. The increases in maize grain yield were 27.94% and 13.24%, respectively. Compared with NT, the differences in the effects of the SRT and RT treatments on maize yield in mild saline-alkali soil were the smallest, being 6.98% and 4.77%, respectively. The relevant results provide guidance on tillage methods and a theoretical basis for improving the properties of different types of soda saline–alkali soils and increasing maize yield. Full article

The Songnen Plain is a significant region in China, known for its high grain production and concentrated distribution of soda saline land. It is also considered a priority area for cropland development in the country. However, the Songnen Plain is now facing prominent issues such as soil salinization, soil erosion, and deteriorating cropland quality, which are exacerbated by climate change and intensified human activities. In order to address these challenges, it is crucial to adjust the quantitative structure and layout of different landscapes in a harmonious manner, aiming to achieve synergistic optimization, which is posed as the key scientific approach to guide comprehensive renovation policies, improve saline–alkaline land conditions, and promote sustainable agricultural development. In this study, four scenarios including natural development, priority food production (PFP), ecological security priority (ESP), and economic–ecological-balanced saline soil improvement were set up based on Nondominated Sorting Genetic Algorithm II (NSGA-II) and the Future Land Use Simulation (FLUS) model. The results demonstrated that the SSI scenario, which focused on economic–ecological equilibrium, displayed the most rational quantitative structure and spatial layout of landscape types, with total benefits surpassing those of the other scenarios. Notably, this scenario involved converting unused land into saline cropland and transforming saline cropland into normal cropland, thereby increasing the amount of high-quality cropland and potential cropland while enhancing the habitat quality of the region. Consequently, the conflict between food production and ecological environmental protection was effectively mitigated. Furthermore, the SSI scenario facilitated the establishment of a robust ecological security and protection barrier, offering valuable insights for land use planning and ecological security pattern construction in the Songnen Plain, particularly in salt-affected areas. Full article

Soil salinization typically exerts a highly negative influence on soil productivity, crop yields, and ecosystem balance. As a typical region afflicted by soil salinization, the soda saline–alkali soils in the Songnen Plain of China demonstrate a clear cracking phenomena. Nevertheless, the overall spectral response to the cracked soil surface has scarcely been studied. This study intends to study the impact of salt parameters on the soil cracking process and enhance the spectral measurement method used for cracked salt-affected soil. To accomplish this goal, a controlled desiccation cracking experiment was carried out on saline soil samples. A gray-level co-occurrence matrix (GLCM) was calculated for the contrast (CON) texture feature to measure the extent of cracking in the dried soil samples. Additionally, spectroscopy measurements were conducted under different surface conditions. Principal component analysis (PCA) was subsequently performed to downscale the spectral data for band integration. Subsequently, the prediction accuracy of back-propagation artificial neural network (BP-ANN) models developed from the principal components of spectral reflectance was compared for different salt parameters. The results reveal that salt content is the dominant factor determining the cracking process in salt-affected soils, and that cracked soil samples had the highest model prediction accuracy for different salt parameters rather than uncracked blocks and 2 mm comparison soil samples. Furthermore, BP-ANN prediction models combining spectral response and CON were further developed, which can significantly enhance the prediction accuracy of different salt parameters with R² values of 0.93, 0.91, and 0.74 and a ratio of prediction deviation (RPD) of 3.68, 3.26, and 1.72 for soil salinity, electrical conductivity (EC), and pH, respectively. These findings provide valuable insights into the cracking mechanism in salt-affected soils, thereby advancing the field of hyperspectral remote sensing for monitoring soil salinization. Furthermore, this study also aids in enhancing the design of spectral measurements for saline–alkali soils and is also helpful for local soil remediation with supporting data. Full article

The improvement of saline-alkali land plays a key role in ensuring food security and promoting agricultural development. Saline soils modifies the response of the soil microbial community, but research is still limited. The effects of applying phosphogypsum with rice cultivation (PRC) on soil physicochemical properties and bacterial community in soda saline-alkali paddy fields in Songnen Plain, China were studied. The results showed that the PRC significantly improved the physicochemical properties of soil, significantly reduced the salinity, increased the utilization efficiency of carbon, nitrogen, and phosphorus, and significantly increased the activities of urease and phosphatase. The activities of urease and phosphatase were significantly correlated with the contents of total organic carbon and total carbon. A redundancy analysis showed that pH, AP, ESP, HCO₃⁻, and Na⁺ were dominant factors in determining the bacterial community structure. The results showed that PRC could improve soil quality and enhance the ecosystem functionality of soda saline-alkali paddy fields by increasing nutrient content, stimulating soil enzyme activity, and regulating bacterial community improvement. After many years of PRC, the soda-alkali soil paddy field still develops continuously and healthily, which will provide a new idea for sustainable land use management and agricultural development. Full article

Soda saline-alkali significantly hinders rice growth, phosphorus utilization efficiency, and yield formation. The application of biochar can alleviate the adverse effects of saline-alkali stress on crops. However, there is limited research on the interaction between biochar and phosphorus fertilizer concerning ionic accumulation, phosphorus utilization efficiency, and rice yield in soda saline-alkali soils. A two-year field experiment was conducted to study the combined effects of biochar and phosphate fertilizer on ionic accumulation, physiological status, phosphorus utilization efficiency, and rice yield in soda saline-alkali soil. Four treatments were established for the study: NK (225 kg N, 75 kg K ha⁻¹ year⁻¹), NPK (225 kg N, 70 kg P, 75 kg K ha⁻¹ year⁻¹), NK + B [225 kg N, 75 kg K ha⁻¹ year⁻¹, 1.5% biochar (w/w)], and NPK + B [225 kg N, 70 kg P, 75 kg K ha⁻¹ year⁻¹, 1.5% biochar (w/w)]. The findings indicated that the combined application of biochar and phosphorus fertilizer (NPK + B) significantly reduced the Na⁺ concentration, Na⁺/K⁺ ratio, malondialdehyde (MDA), superoxide anion (O₂⁻), and hydrogen peroxide (H₂O₂) levels in rice plants. Furthermore, it resulted in a significant increase in K⁺ concentration and elevated the levels of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), proline (Pro), soluble protein (SP), soluble sugar (SS), and acid phosphatase (ACP). The NPK + B treatment exhibited a significant difference compared to the other treatments (p < 0.05). Compared with NK, phosphorus accumulation and phosphorus utilization efficiency under NPK + B were significantly increased (p < 0.05). The average of biomass yield, grain yield, and harvest index of NPK + B, NK + B, and NPK significantly surpassed those of NK by 6.28–12.25%, 19.80–42.13%, and 11.59–24.64%, respectively. Moreover, a significant difference was observed between NPK + B and the other treatments (p < 0.05). Principal component analysis of the two-year mean data revealed a strong positive correlation of 89.5% for PC1 and a minor negative correlation of 4.4% for PC2. Our research findings demonstrate that the combination of biochar and phosphorus fertilizer effectively enhances salt and alkali tolerance in rice plants, resulting in increased yield through improved ionic balance and physiological status. Full article

Climate change and aridification have increased the risk of salinization and organic carbon loss in dryland soils. Enrichment using biochar and organic fertilizers has the potential to reduce salt toxicity and soil carbon loss. However, the effects of biochar and organic fertilizers on CO₂ and CH₄ emissions from saline soils in dryland areas, as well as their microbial mechanisms, remain unelucidated. To clarify these issues, we performed a 5-month incubation experiment on typical soda-type saline soil from the western part of the Songnen Plain using five treatments: control treatment (CK), 5% urea (U), straw + 5% urea (SU), straw + 5% urea + microbial agent (SUH), and straw + 5% urea + biochar (SUB). Compared with the SU treatment, the SUH and SUB treatments reduced cumulative CO₂ emissions by 14.85% and 35.19%, respectively. The addition of a microbiological agent to the SU treatment reduced the cumulative CH₄ emissions by 19.55%, whereas the addition of biochar to the SU treatment increased the cumulative CH₄ emissions by 4.12%. These additions also increased the relative abundances of Proteobacteria, Planctomycetes, and Ascomycota. Overall, the addition of biochar and organic fertilizer promoted CO₂ emissions and CH₄ uptake. This was mainly attributed to an improved soil gas diffusion rate due to the addition of organic materials and enhanced microbial stress due to soil salinity and alkalinity from the release of alkaline substances under closed-culture conditions. Our findings have positive implications for enhancing carbon storage in saline soils in arid regions. Full article

The precise quantification of soil salinity and the spatial distribution are paramount for proficiently managing and remediating salinized soils. This study aims to explore a pioneering methodology for forecasting soil salinity by combining the spectroscopy of soda saline–alkali soil with crack characteristics, thereby facilitating the ground-based remote-sensing inversion of soil salinity. To attain this objective, a surface cracking experiment was meticulously conducted under controlled indoor conditions for 57 soda saline–alkali soil samples from the Songnen Plain of China. The quantitative parameters for crack characterization, encompassing the length and area of desiccation cracks, together with the contrast texture feature were methodically derived. Furthermore, spectral reflectance of the cracked soil surface was measured. A structural equation model (SEM) was then employed for the estimation of soil salt parameters, including electrical conductivity (EC_1:5), Na⁺, pH, HCO₃⁻, CO₃²⁻, and the total salinity. The investigation unveiled notable associations between different salt parameters and crack attributes, alongside spectral reflectance measurements (r = 0.52–0.95), yet both clay content and mineralogy had little effect on the cracking process due to its low activity index. In addition, the presence of desiccation cracks accentuated the overall spectral contrast of salt-affected soil samples. The application of SEMs facilitated the concurrent prediction of multiple soil salt parameters alongside the regression analysis for individual salt parameters. Nonetheless, this study confers the advantage of the swift synchronous observation of multiple salt parameters whilst furnishing lucid interpretation and pragmatic utility. This study helps us to explore the mechanism of soil salinity on the surface cracking of soda saline–alkali soil in the Songnen Plain of China, and it also provides an effective solution for quickly and accurately predicting soil salt content using crack characteristics, which also provides a new perspective for the hyperspectral measurement of saline–alkali soils. Full article

Soda saline–alkaline stress significantly impedes the rice grain filling process and ultimately impacts rice yield. Biochar has been shown to mitigate the negative impacts of saline–alkaline stress on plants. However, the exact mechanism by which biochar influences the rice grain-filling rate in soda saline–alkaline soil is still not fully understood. A two-year field experiment was conducted with two nitrogen fertilizer levels (0 and 225 kg ha⁻¹) and five biochar application rates [0% (B0), 0.5% (B1), 1.5% (B2), 3.0% (B3), and 4.5% (B4) biochar, w/w]. The results demonstrated that biochar had a significant impact on reducing the Na⁺ concentration and Na⁺/K⁺ ratio in rice grown in soda saline–alkaline lands, while also improving its stress physiological conditions. B1, B2, B3, and B4 showed a notable increase in the average grain-filling rate by 5.76%, 6.59%, 9.80%, and 10.79%, respectively, compared to B0; the time to reach the maximum grain-filling rate and the maximum grain weight saw increases ranging from 6.02% to 12.47% and from 7.85% to 14.68%, respectively. Meanwhile, biochar, particularly when used in conjunction with nitrogen fertilizer, notably enhanced the activities of sucrose synthase (SuSase), ADPG pyrophosphorylase (AGPase), starch synthase (StSase), and starch branching enzyme (SBE) of rice grains in soda saline–alkaline lands. Furthermore, rice yield increased by 11.95–42.74% in the B1, B2, B3, and B4 treatments compared to the B0 treatment. These findings showed that biochar improves yield by regulating ionic balance, physiological indicators, starch synthesis key enzyme activities, and the grain-filling rate in soda saline–alkaline paddy fields. Full article

Hyperspectral technology is widely recognized as an effective method for monitoring soil salinity. However, the traditional sieved samples often cannot reflect the true condition of the soil surface. In particular, there is a lack of research on the spectral response of cracked salt-affected soils despite the common occurrence of cohesive saline soil shrinkage and cracking during water evaporation. To address this research, a laboratory was designed to simulate the desiccation cracking progress of 57 soda saline–alkali soil samples with different salinity levels in the Songnen Plain of China. After completion of the drying process, spectroscopic analysis was conducted on the surface of all the cracked soil samples. Moreover, this study aimed to evaluate the predictive ability of multiple linear regression models (MLR) for four main salt parameters. The hyperspectral reflectance data was analyzed using three different band screening methods, namely random forest (RF), principal component analysis (PCA), and Pearson correlation analysis (R). The findings revealed a significant correlation between desiccation cracking and soil salinity, suggesting that salinity is the primary factor influencing surface cracking of saline–alkali soil in the Songnen Plain. The results of the modeling analysis also indicated that, regardless of the spectral dimensionality reduction method employed, salinity exhibited the highest prediction accuracy for soil salinity, followed by electrical conductivity (EC) and sodium (Na⁺), while the pH model exhibited the weakest predictive performance. In addition, the usage of RF for band selection has the best effect compared with PCA and Pearson methods, which allows salt information of soda saline–alkali soils in Songnen Plain to be predicted precisely. Full article

The mercury cell manufacturing process, which has been extensively used in chlor-alkali plants to produce chlorine and caustic soda by electrolysis, represents a major source of Hg environmental pollution. At Saline di Volterra (Tuscany, Italy), solution mining by pumping water into halite deposits was applied to produce brines for a mercury-cell chlor-alkali plant. The Hg-contaminated, exhausted brines were pumped back at depth into the rock salt field in order to renew the available resources. Activities ceased in 1994, following the leakage dispersion of highly contaminated Hg(0)-bearing brines into the environment. The mercury content in the soil, measured during a survey conducted in 2000, reached 334 mg/kg, highlighting diffuse contamination in the floodplain. By 2009, the Hg concentration had generally decreased and was mostly confined to the topsoil layer. In order to evaluate the present Hg soil pollution, a geochemical survey was carried out in 2023, almost thirty years after the contamination event. The obtained data indicated the occurrence of legacy Hg, which reached 25.5 mg/kg in some soil samples. Speciation analysis for the most contaminated soil revealed that Hg(0) represented about 17.3% of the total Hg and that water-soluble and organic Hg fractions were negligible. These results suggest that the originally released metallic mercury has volatilized and likely oxidized, becoming practically immobile in the soil. A risk assessment, performed by applying Hg speciation analysis, indicated that the mercury in the soil does not carry a risk of non-cancerous effects for different exposure routes in case of subsequent use of the site and that the formerly contaminated area can now be converted into a leisure area. Full article