Properties Of Saline Soil Research Articles

Assessment of the Effects of Biochar on the Physicochemical Properties of Saline–Alkali Soil Based on Meta-Analysis

Enhancing global agricultural sustainability critically requires improving the physicochemical properties of saline–alkali soil. Biochar has gained increasing attention as a strategy due to its unique properties. However, its effect on the physicochemical properties of saline–alkali soil varies significantly. This study uses psychometric meta-analysis across 137 studies to synthesize the findings from 1447 relatively independent data sets. This study investigates the effects of biochar with different characteristics on the top 20 cm of various saline–alkali soils. In addition, aggregated boosted tree (ABT) analysis was used to identify the key factors of biochar influencing the physicochemical properties of saline soils. The results showed that biochar application has a positive effect on improving soil properties by reducing the sodium adsorption ratio (SAR) and the exchangeable sodium percentage (ESP) by 30.31% and 28.88%, respectively, with a notable 48.97% enhancement in cation exchange capacity (CEC). A significant inverse relationship was found between soil salinity (SC) and ESP, while other factors were synergistic. Biochar application to mildly saline soil (<0.2%) and moderately saline soil (0.2–0.4%) demonstrated greater improvement in soil bulk density (SBD), total porosity (TP), and soil moisture content (SMC) compared to highly saline soil (>0.4%). However, the reduction in SC in highly saline soil was 4.9 times greater than in moderately saline soils. The enhancement of soil physical properties positively correlated with higher biochar application rates, largely driven by soil movements associated with the migration of soil moisture. Biochar produced at 401–500 °C was generally the most effective in improving the physicochemical properties of various saline–alkali soils. In water surplus regions, for mildly saline soil with pH < 8.5, mixed biochar (pH 6–8) at 41–80 t ha−1 was the most effective in soil improvement. Moreover, in water deficit areas with soil at pH ≥ 8.5, biochar with pH ≤ 6 applied at rates of >80 t ha−1 showed the greatest benefits. Agricultural residue biochar showed superior efficiency in ameliorating highly alkaline (pH ≥ 8.5) soil. In contrast, the use of mixed types of biochar was the most effective in the amelioration of other soil types.

Effects of Long-Term Reed Plantation on Saline Habitat

In recent years, the improvement and utilization of saline-alkaline soil has gradually shifted from engineering measures to biological measures. As a salt-tolerant plant, the reed has been preliminarily proven to have a role in improving saline-alkaline land. In order to explore the long-term effect of planting unharvested reeds on the improvement of saline-alkaline land, a pilot plot was set up in Fuping Pilot Test Base (34° 42'180"E; 109°11'49" N) near Lubo Beach, Fuping, Shaanxi, in 2012 to ascertain the improvement effect of long-term reed cultivation on saline–alkaline land. The objective was to study the long-term changes in soil pH, electrical conductivity, Ca2+, Mg2+, Cl-, SO42-, HCO3-, and CO32- contents, soil particle size and soil fertility. Results showed that (i) reed cultivation could effectively reduce soil salinization in the long term. From 2012 to 2022, the average pH of saline soil decreased from 9.42 to 8.86, and the electrical conductivity decreased from 1.20 μS/cm to 0.70 μS/cm. (ii) Reed cultivation considerably reduced the contents of Ca2+, Mg2+, Cl-, SO42-, HCO3-, and CO32- in the soil in the long term, and the reduction in each index was 5.9, 41.7, 63.5, 90.6, 81.7, 90.6, 77.9and 90.3%, respectively. (iii) Reed cultivation changed the soil structure. The soil texture of the 0–60 cm soil layer changed from silty sandy loam to silty loam from 2018 to 2022. (iv) Long-term reed planting without harvesting effectively improved soil fertility. In 2012, the content of soil organic matter was only 2.74 g/kg, but in 2022, the value reached 12.8 g/kg. Reed planting improved the physical and chemical properties of saline soil. Therefore, biological restoration of reed can be considered in low-lying saline–alkaline areas with high water volumes. Bangladesh J. Bot. 53(3): 665-672, 2024 (September) Special

Effect of Combined Application of Wood Vinegar Solution and Biochar on Saline Soil Properties and Cotton Stress Tolerance.

Biomass pyrolysis by-products, such as biochar (BC) and wood vinegar (WV), are widely used as soil conditioners and efficiency enhancers in agriculture. A pot experiment was conducted to examine the effects of WV, both alone and in combination with BC, on soil properties in mildly saline soil and on cotton stress tolerance. The results demonstrated that BC and WV application, either individually or together, increased soil nutrient content. The combined application was more effective than the individual applications, resulting in a 5.18-20.12% increase in organic matter, a 2.65-15.04% increase in hydrolysable nitrogen, a 2.23-58.05% increase in effective phosphorus, and a 2.71-29.38% increase in quick-acting potassium. Additionally, the combined application of WV and BC led to greater improvements in cotton plant height, net photosynthetic rate (Pn), leaf nitrate reductase (NR), superoxide dismutase (SOD), and catalase (CAT) activities compared to the application of BC or WV alone. The enhancements in this study varied across different parameters. Plant height showed an increase of 14.32-21.90%. Net photosynthetic rate improved by 13.56-17.60%. Leaf nitrate reductase increased by 5.47-37.79%. Superoxide dismutase and catalase showed improvements of 5.82-64.95% and 10.36-71.40%, respectively (p < 0.05). Moreover, the combined treatment outperformed the individual applications of WV and BC, resulting in a significant decrease in MDA levels by 2.47-51.72% over the experimental period. This combined treatment ultimately enhanced cotton stress tolerance. Using the entropy weight method to analyze the results, it was concluded that the combined application of WV and BC could enhance soil properties in mildly saline soils, increase cotton resistance, and hold significant potential for widespread application.

Investigating the influence of eco-friendly approaches on saline soil traits and growth of common bean plants (Phaseolus vulgaris L.).

Soil salinization significantly impacts agricultural lands and crop productivity in the study area. Moreover, freshwater scarcity poses a significant obstacle to soil reclamation and agricultural production. Therefore, eco-friendly strategies must be adopted for agro-ecosystem sustainability under these conditions. A study conducted in 2022 and 2023 examined the interaction effects of various soil mulching materials (unmulched, white plastic, rice straw, and sawdust) and chitosan foliar spray application (control, 250 mg L-1 of normal chitosan, 125 mg L-1 of nano chitosan, and 62.5 mg L-1 of nano chitosan) on the biochemical soil characteristics and productivity of common beans in clay-saline soil. Higher organic matter, available nutrient content, and total bacteria count in soils were found under organic mulching treatments (rice straw and sawdust). In contrast, the white plastic mulching treatment resulted in the lowest values of soil electrical conductivity (EC) and the highest soil water content. Conversely, chitosan foliar spray treatments had the least impact on the chemical properties of the soil. Plants sprayed with 62.5 mg L-1 of nano chitosan exhibited higher chlorophyll content, plant height, fresh weight of shoots and roots, seed yield, and nutrient content compared to other chitosan foliar spray applications. All treatments studied led to a significant reduction in fungal communities and Na% in plants. The combined effect of organic mulch materials and foliar spray application of 62.5 mg L-1 nano chitosan appeared to enhance biochemical saline soil properties and common bean productivity.

Gypsum and organic materials improved soil quality and crop production in saline-alkali on the loess plateau of China

Arable soil and crop productivity are severely affected by salinization. Therefore, soil amendments are an important measure for improving saline-alkali soil for agricultural development. Desulfurized gypsum is a common soil amendment that has been used repeatedly alongside organic materials to improve the biological, physical, and chemical properties of saline soil. This study takes the typical saline-alkali farmland soil in Yulin as the research object, and five treatments were established: a blank treatment (CK), a single application 2.5 t ha−1 of desulfurized gypsum (T), 2.5 t ha−1 of desulfurized gypsum and 1.5 t ha−1 of green manure (TL), application 2.5 t ha−1 of desulfurized gypsum and 1.5 t ha−1 of straw (TS), and 2.5 t ha−1 of desulfurized gypsum and 1.5 t ha−1 of organic fertilizer (TV). The results show that the TV treatment achieved a significant improvement in soil nutrients, organic carbon, enzyme activity, and maize yield. In 2022 (2023), the compared of organic matter, TN, TP, TK, AP, and AK increased significantly compared with the CK treatment when the TV treatment was applied. Soil phosphatase activity (SPA), soil urease activity (SUA) and soil sucrase activity (SSA) significantly higher in the TV treatment compared with the other treatments and increased significantly over the two-year period. Furthermore, soil organic carbon (SOC), easily oxidizable organic carbon (EOC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC) also significantly increased with the 2022 and 2023 TV treatments. Correlation analysis revealed a positive relationship between maize yield and soil nutrients, organic carbon, and enzyme activity (P &amp;lt; 0.05). Thus, the TV treatment was determined to be the optimal treatment for soil improvement. This conclusion was supported by analyses performed using membership function analysis, gray correlation analysis, and entropy TOPSIS model evaluation. Therefore, this method increases soil quality, improves soil fertility, achieves high maize yields, and provides a scientific basis for enhancing and utilizing saline-alkali soil in the Loess Plateau.

Properties of saline soil stabilized with fly ash and modified aeolian sand

Against the backdrop of saline soil solidification and the resource utilization of solid waste and aeolian sand in cold and arid regions, this study employs locally accessible fly ash and aeolian sand to solidify saline soil. By combining unconfined compressive strength tests, X-ray diffraction analysis, scanning electron microscopy, orthogonal experiments, and single-factor analysis, the strength characteristics, mineral composition, and interfacial structure changes of saline soil solidified with different freeze-thaw cycles and varying amounts of fly ash, aeolian sand, and alkali activators were investigated. The effects of each factor were analyzed to determine the optimal mixture ratio and to explore the solidification mechanism.The results indicate that the unconfined compressive strength of saline soil is most significantly enhanced when solidified with a combination of fly ash, aeolian sand, and alkali activators. The optimal mixture ratio was found to be 24 % fly ash, 7 % aeolian sand, and 4.5 mol/L alkali activator. With the incorporation of these solidifying materials, the failure mode of saline soil transitions from plastic to brittle, and the stress-strain curve exhibited a strain-softening behavior. The combined solidification method demonstrated the most pronounced effect in mitigating freeze-thaw damage, with the unconfined compressive strength of the solidified soil reaching 7.01 MPa after seven freeze-thaw cycles, compared to 0.03 MPa for the untreated soil, an increase by a factor of 234.This significant enhancement is attributed to the formation of substantial gel substances, which mitigate the strength loss caused by freeze-thaw cycles. The gel locking mechanism between particles in the solidified soil far exceeds the detrimental effects of freeze-thaw cycles, effectively inhibiting freeze-thaw deterioration. Additionally, the reaction pathways involving AFt and AFm phases reduce the content of SO42- and Cl- in the solidified soil, effectively suppressing salt expansion and significantly improving the soil's strength.

High-throughput 16S rRNA gene-based amplicon sequencing reveals the functional divergence of halophilic bacterial communities in the Suaeda salsa root compartments on the eastern coast of China

The rhizosphere environment of plants, which harbors halophilic bacterial communities, faces significant challenges in coping with environmental stressors, particularly saline soil properties. This study utilizes a high-throughput 16S rRNA gene-based amplicon sequencing to investigate the variations in bacterial community dynamics in rhizosphere soil (RH), root surface soil (RS), root endophytic bacteria (PE) compartments of Suaeda salsa roots, and adjoining soils (CK) across six locations along the eastern coast of China: Nantong (NT), Yancheng (YC), Dalian (DL), Tianjin (TJ), Dongying (DY), and Qingdao (QD), all characterized by chloride-type saline soil. Variations in the physicochemical properties of the RH compartment were also evaluated. The results revealed significant changes in pH, electrical conductivity, total salt content, and ion concentrations in RH samples from different locations. Notably, the NT location exhibited the highest alkalinity and nitrogen availability. The pH variations were linked to HCO3− accumulation in S. salsa roots, while salinity stress influenced soil pH through H+ discharge. Despite salinity stress, enzymatic activities such as catalase and urease were higher in soils from various locations. The diversity and richness of bacterial communities were higher in specific locations, with Proteobacteria dominating PE samples from the DL location. Additionally, Vibrio and Marinobacter were prevalent in RH samples. Significant correlations were found between soil pH, salinity, nutrient content, and the abundance and diversity of bacterial taxa in RH samples. Bioinformatics analysis revealed the prevalence of halophilic bacteria, such as Bacillus, Halomonas, and Streptomyces, with diverse metabolic functions, including amino acid and carbohydrate metabolisms. Essential genes, such as auxin response factor (ARF) and GTPase-encoding genes, were abundant in RH samples, suggesting adaptive strategies for harsh environments. Likewise, proline/betaine transport protein genes were enriched, indicating potential bioremediation mechanisms against high salt stress. These findings provide insight into the metabolic adaptations facilitating resilience in saline ecosystems and contribute to understanding the complex interplay between soil conditions, bacterial communities, and plant adaptation.

Improving Physical and Chemical Properties of Saline Soils with Fly Ash Saline and Alkaline Amendment Materials

Studies have demonstrated that the physicochemical properties of saline soils can be improved, and crop growth can be promoted by fly ash saline and alkaline soil amendment materials. Herein, the effects of fly ash saline and alkaline soil amendment materials on the physical and chemical properties of saline soil and growth conditions of Arrhenatherum elatius at room temperature were evaluated. Meanwhile, planting experiments of Zea mays L. were conducted in the demonstration field of saline–alkaline land amendment in Yinchuan, Ningxia. The results showed that the application of amendment materials significantly (p &lt; 0.05) improved saline soil’s physical and chemical properties. The saline soil pH decreased from an average of 10.51 to 8.89; the Na+ content decreased from an average of 2.93 g·kg−1 to 0.7 g·kg−1 after 25 days of action. In addition, the soil bulk density decreased from an average of 1.49 g·cm−3 to 1.36 g·cm−3, and the total porosity increased by 15.60%. Soil available phosphorus and available potassium content also increased significantly, with mean values increasing from 6.74 mg·kg−1 and 173 mg·kg−1 to 58.30 mg·kg−1 and 330.76 mg·kg−1, respectively. In addition, the plant height and stem thickness of Arrhenatherum elatius increased from an average of 11.76 cm, 1.28 mm to 21.72 cm, 1.59 mm with the application of 2.5 wt% amendment material. The plant height and stem thickness of Zea mays L. increased from mean values of 210 cm and 21.94 mm to 315.7 cm and 26.75 mm, respectively, when 0.07 t·hm−2 of amendment material was applied in the field. Overall, it was concluded that applying fly ash saline and alkaline soil amendment materials improves the physicochemical properties of saline soils, reducing saline stress and promoting the growth of Arrhenatherum elatius and Zea mays L.

Effect of biochar on biochemical properties of saline soil and growth of rice

To amend physical properties of coastal saline soil for rice production, six biochar treatments (0, 0.5, 1, 2, 4 and 6 kg biochar per m2 soil) were set up as CK, T1, T2, T3, T4 and T5, respectively and their effect on the biochemical properties of coastal saline soil and rice growth characteristics were evaluated in a barrel planting experiment. The results showed that compared with CK (with no biochar added), the soil EC of T1 and T2-T5 was reduced by 11.5 %, but increased by 8.8–62.9 %, respectively. The available potassium and organic matter contents of T1-T5 increased ranging from 3.7-10.2 % to 8.0–46.8 %, respectively. With the increase of the biochar amount, the urease activity of soil in the 0–10 cm deep soil showed an increasing trend by 194.8–744.6 % with T1-T5, compared with that of the CK treatment. The activity of alkaline phosphatase in soil increased first and then decreased, and its increment with T1-T5 was between 28.2 and 64.8 % in comparison with that of CK. With more biochar added to soil, the leaf dry weight, root dry weight, total dry matter mass, total root length, single panicle quality and weight per 100 grains showed a trend of increase first and then decrease. The highest incremental values of all measurements were obtained with T1 by 21.8 %, 23.9 %, 13.8 %, 33.9 %, 30.8 % and 11.6 % respectively, compared with those with CK. However, adding biochar in soil demonstrated insignificant effect on the weight of single panicle, panicle length, stem thickness, tillers, setting rate, soil hydrolyzable nitrogen, available phosphorus content, rice protein, amylose, and taste quality among all treatments. In summary, the application of 0.5 kg m−2 biochar can improve the biochemical properties of saline soil and therefore increase rice yield.

Organic fertilizer and hydrothermal conditions change the distribution of Medicago sativa L. productivity and soil bacterial diversity in coastal saline soil

BackgroundAlfalfa (Medicago sativa L.) is a perennial leguminous forage that can improve the properties of saline soil. In addition, the supplementation with fertilizer to promote soil bacterial activity is critical to improve the productivity of coastal saline soils. However, the association between fertilizer application, bacterial community characteristics, and alfalfa yield in saline soil remains unclear.AimTo understand the interaction of different fertilizer and environmental factors on soil bacterial diversity and alfalfa yield in coastal saline soil.ResultsA 4-year field study was conducted to examine the interaction of different fertilizer treatments and environmental factors on soil bacterial diversity and alfalfa yield in coastal saline soil in China. Three organic fertilizer treatments (fulvic acid potassium, fulvic acid potassium + wood vinegar, and fulvic acid potassium + Bacillus), one biochar treatment (bio-charcoal), one inorganic fertilizer treatment (diammonium phosphate), and a control (no fertilizer) were included. The effects of the six treatments and 15 cutting times on alfalfa yield and soil bacterial community diversity were assessed. The productivity in fulvic acid potassium + Bacillus and fulvic acid potassium treatments was 68.37 and 67.90 t·hm−2 in 4 years, which was significantly higher than that in the bio-charcoal treatment and control. Hydrothermal conditions and timing of alfalfa harvest had significant effects on the soil bacterial community. Proteobacteria, Acidobacteria, and Actinobacteria were the principal bacterial phyla detected in the soil samples, collectively accounting for approximately 60% of the total bacterial abundance. The relative abundance of Bacteroidetes, Firmicutes, and Nitrospirae was significantly correlated with alfalfa yield, and the abundance of these phyla was also affected by the maximum temperature and precipitation. Fertilizer supplementation in coastal saline soil can effectively increase the yield of alfalfa. Among the fertilizers tested, fulvic acid potassium had the strongest effect, whereas bio-charcoal fertilizer had little effect on alfalfa yield.Graphical

Improving the Properties of Saline Soil Using a Deep Soil Mixing Technique

Saline soils belong to the category of problematic soils with high compressibility and weak shear strength when exposed to water. Water dissolves the salts in soils which are the primary cementing agents. Therefore, stabilization methods that provide sustainable cementing substances are employed in this study using deep soil mixing techniques to enhance the properties of saline soil. In this regard, a laboratory-scaled deep soil mixing procedure was developed to treat the soil in a way similar to the field methods. A binder, consisting of marble powder and cement, was employed to treat the soil. This study aimed to select the most efficient binder mix design in terms of optimum marble powder/cement ratio and optimum water/binder ratio. Unconfined compressive strength, durability, density measurements and ultrasonic velocity pulse tests were conducted on the treated soil. To determine the treatment efficacy, microstructure analysis of the treated samples was conducted. The 80C20MP and 70C30MP samples exhibit a dense soil structure with minimal voids, and their microstructure is denser than the other treated specimens. Additionally, the EDX analysis shows increased calcium percentages with up to 30% MP replacement, aligning well with the microstructure analysis and the UCS values. The results indicate that the economical and eco-friendly binder mix consisted of (70% to 80%) cement and (20% to 30%) marble powder with water/binder ratio in the range of 1.1 to 1.3. This mix contributed greatly to the improvement in soil strength and integrated columns.

Research Advances in the Impacts of Biochar on the Physicochemical Properties and Microbial Communities of Saline Soils

The scientific management of salinized agricultural lands and the use of undeveloped saline lands to ensure food security have become one of the most urgent tasks nowadays. Biochar contains rich carbon (C) and functional groups, and processes high alkalinity, porosity, and specific surface area (SSA). Thus, it has been widely used as an effective organic conditioner in acidic or neutral soils to improve their fertility. However, so far, the impacts of biochar application on properities of saline soils and the underlying mechanisms remain unveiled. Therefore, in this study, we focus on the investigation of the impacts of biochar on the physical, chemical, and biological properties of saline soils. We found that biochar could: (1) decrease soil bulk density (BD), increase soil porosity, promote the formation of soil aggregation and enhance the leaching of soil salts; (2) increase the cation exchange capacity (CEC) of soil, decrease the salinity of soil through ion exchange and adsorption; (3) directly act as the nutrient supplements, indirectly adsorb water and nutrients or improve nutrient availability (e.g., soil organic carbon (SOC) turnover and sequestration, nutrient cycling); and (4) improve the structure and functioning of the soil microbial community and therefore indirectly impact the C, nitrogen (N) and phosphorus (P) cycling in soil systems. However, these impacts heavily depend on the properties, the concentration of the biochar added to the soil, and the type and location of the soil. In fact, some studies have shown that the addition of biochar in soil could even increase the salinity of saline soils. Another issue is the lack of long-term and large-scale field experiments regarding the impact of biochar addition on properties of saline soils. Therefore, future studies should focus on long-term field experiments with the combination of traditional soil analytical methods and mordern molecular techniques (e.g., high-throughput sequencing, macro-genomics, and metabolomics) to comprehensively reveal the response mechanism of physicochemical properties and microbial characteristics of saline soils to exogenous biochar. Our study can provide a scientific foundation for the practical agricultural production and ecological management of biochar.

Study of Mechanical Properties of Saline Soils under Different Stress Paths

The stress path is a critical factor affecting the mechanical properties of saline soils. In order to study the mechanical properties of saline soils under different stress paths, in situ saline soils in the Qian’an area of western Jilin province were selected for this study, and triaxial shear tests under six different stress paths were conducted, including the consolidated undrained triaxial test under the conventional stress path under the isobaric consolidation condition; the consolidated drained triaxial test under the conventional, equal p, reduced p, and increased p stress paths under the isobaric consolidation condition; and the consolidated drained triaxial test under the conventional stress path under the K0 consolidation condition. The effects of the consolidation conditions, drainage conditions, and stress paths on the mechanical properties of in situ saline soils were investigated. The results reveal that the stress–strain relationship curves of soil samples decrease continuously in the order of increased p, conventional, equal p, and decreased p, and they all show the characteristics of strain hardening. The stress path curves have the same slope under the same stress path. For different confining pressures, only the relative positions of the curves are different. Under the conventional stress path, the slope is 1; under the increased p stress path, the slope is 1/3; under the equal p stress path, the slope is 3; and under the decreased p stress path, the slope of the curve is −1. For the same confining pressure, the magnitude relationships of shear strength under the different stress paths are as follows: increased p &gt; conventional &gt; equal p &gt; decreased p. For the cohesion c and internal friction angle φ, the consolidation condition has a greater effect on the cohesion c and a smaller effect on the internal friction angle φ; the drainage condition has a smaller effect on the cohesion c and a larger effect on the internal friction angle φ; and the stress paths have a greater effect on both cohesion c and internal friction angle φ.

The synergistic effect of biochar and poly(2-ethyl-2-oxazoline)/poly(2-hydroxyethylmethacarylate)/chitosan) hydrogels on saline soil properties and carrot productivity

BackgroundSoil salinity is one of the most important factors limiting crop production. Furthermore, with the increasing population and saline soil worldwide there is no choice but to utilize saline soil to increase the agricultural regions. Therefore, to improve carrot productivity under saline conditions, it is necessary to provide good management such as applying hydrogels and biochar for improving soil properties.MethodologyHydrogels (PEtOx-HEMA-CS) were synthesized from poly (2-ethyl-2-oxazoline), 2-hydroxyethyl methacrylate (HEMA as crosslinker) and chitosan (CS) via exposure those to gamma irradiation dose; 30 kGy of dose rate 0.9 kGy/h and obtained three types of hydrogels according to concentration of chitosan used. The PEtOx-HEMA-CS hydrogels were enhanced water holding capacity for agriculture purposes. The chemical structures of obtained hydrogels were characterized by FTIR, XRD and SEM. The swelling (%) and gelation (%) were determined. Biochar (BC) as an active substance was physically mixed with those hydrogels at various ratios (0/100, 0.5/99.5, 1/99 and 100/0 (g/g) biochar/hydrogels). BC, PEtOx-HEMA-CS and the mixture of PEtOx-HEMA-CS-BC were mixed with saline soil at ratio 0.05% and 0.1% w/w of obtained materials/soil. A pot experiment was conducted to mitigate the salinity hazards on carrot productivity using biochar with and without hydrogels. Mean maximum temperature, minimum temperature, precipitation, relative humidity and wind speed from September to December in the studied region are 28.66 ℃, 15.76 ℃, 0.01 mm, 58.81%, 5.94 km/h, respectively.FindingsThe obtained data referred that there is a significant decrease in soil salinity and exchangeable sodium percentage and increase in organic matter, cation exchange capacity, field capacity, permanent wilting point and available water especially at (PEtOx-HEMA-CS5)0.1-BC1. The highest increment percentage of nitrogen, phosphorous and potassium were 36.36%, 70% and 72%, respectively. In addition, the relative increase of carrot productivity was 49.63% at the highest rates of biochar and hydrogels. However, the highest value of water use efficiency was observed at the mixture of biochar and hydrogels at (PEtOx-HEMA-CS5)0.1-BC1.ConclusionsFinally, applying biochar combined with (PEtOx-HEMA-CS5) could be recommended as a good approach to improve carrot productivity and water use efficiency under saline soil conditions.Graphical

Effect of dry-wet cycles on the mechanical properties of saline soil solidified with sulfur-free lignin and hydrophobic polymer

In response to the increasing problem of rainfall-induced erosion-concomitant slope failure in saline soil areas, environmentally friendly and recyclable bioethanol by-product sulfur-free lignin (SFL) and green pollution-free hydrophobic polymer (HP) were used to improve the engineering performance of saline soil. The effect of dry-wet cycles on the physicochemical properties of solidified saline soil was investigated by performing unconfined compressive strength tests (UCS) and microscopic analyses. The results showed that the optimal mixture of solidified soil was 5% SFL and 12% HP, which increased the strength by 274.29% compared to plain soil (PS). The dry-wet cycle leads to the deterioration of the microstructure and pore characteristics of the soil, with a strength deterioration rate (SDR) of 45.1% after 10 dry-wet cycles. And the solidification mechanism was attributed to the hydrophobic matrix and ion exchange generated by SFL and HP, which enhanced the particle aggregation and microstructural strength of saline soil.

Long‐term rice cultivation improved coastal saline soil properties and multifunctionality of subsoil layers

AbstractRice cultivation has been found to be an effective and feasible approach for improving saline soils and increasing food production. Most studies on the improvement of rice cultivation on saline soil have focused on the several individual soil properties in the topsoil, and we know little about the importance of rice cultivation for improving multifunctionality in coastal saline soils. We investigated basic soil properties (soil physical sand content, soil physical clay content, pH, EC, soil organic carbon, total nitrogen, alkaline hydrolysis nitrogen, available potassium, available phosphorus), enzyme activities (urease, catalase, protease) and soil multifunctionality (SMF) in 0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm and 80–100 cm soil layers with rice cultivated for 0 (tidal flat; CK), 20 (R20), 44 (R44) and 70 years (R70). We found that soil EC was alleviated markedly in the first 20 years after rice cultivation. Soil physical sand content, pH, EC and available potassium (AK) decreased while total nitrogen (TN), alkaline hydrolysis nitrogen (AN), urease (URE), catalase (CAT) activities and SMF increased with the increase in rice cultivation years. The highest soil total organic carbon (SOC) was shown in R44. Soil pH, EC, AK and physical sand content increased while SOC, TN, AN, enzyme activities decreased with the increase in soil depth. Redundancy (RDA) analysis showed soil physicochemical properties explained 97.53% of the variation in soil enzyme activities. Soil CAT, URE and protease (PRO) had a positive correlation with soil physical clay content, SOC, TN, AN and AP while negatively correlated with pH and AK. The increased SOC and clay content by rice cultivation might be the main reasons stimulating soil enzyme activities. In summary, long‐term rice cultivation could alleviate soil salinity, increased SMF down to 1 m, implying that rice cultivation effectively improved coastal saline soil, and the improvement could last for 70 years.

Synergistic improvement of carbon sequestration and crop yield by organic material addition in saline soil: A global meta-analysis

The improvement and utilization of saline soil is an important guarantee for cultivating healthy soil, ensuring global food security, and mitigating the negative impacts of climate change. Organic material addition plays a crucial role in soil improvement and remediation, soil carbon sequestration, and improving soil fertilizer and productivity. In order to explore the comprehensive impact of organic material addition on properties of saline soil (including the physical and chemical properties, nutrient fixation, crop yield, and carbon sink capacity), we conducted a global meta-analysis using data from 141 articles. We found that, soil salinization significantly reduced plant biomass (50.1 %), soil organic carbon (20.6 %), and microbial biomass carbon (36.5 %). Meanwhile, it also reduced CO2 flux (25.8 %) and CH4 flux (90.2 %) significantly. Adding organic materials to saline soil significantly increased crop yield (30.4 %), plant biomass (30.1 %), soil organic carbon (62.2 %), and microbial biomass carbon (78.2 %), but also increased CO2 flux (221.9 %) and CH4 flux (29.7 %). Considering the balance of both carbon sequestration and carbon emissions, organic material addition significantly increased the net carbon sequestration by about 5890.7 kg CO2-eq·hm−2·100 d−1 on average. Besides, the organic material addition reduced soil salinity, exchangeable sodium, and pH, and increased >0.25 mm aggregates and soil fertility. Our findings suggest that organic material addition can improve both carbon sequestration in saline soil and crop yield. Considering the huge area of saline soil around the world, this understanding is essential to reduce the saline obstacle, improve the soil carbon sink capacity, ensure food security, and increase farmland reserves.

Spatiotemporal Variation in Saline Soil Properties in the Seasonal Frozen Area of Northeast China: A Case Study in Western Jilin Province

Due to the impact of climate change and human activities, the problem of soil salinization is increasingly prominent, posing a threat to the safety of the ecological environment and engineering construction. To understand the development tendency of soil salinization, this paper took the saline soil in Western Jilin province as the research object and carried out a long–term investigation into the basic properties of the soil at several monitoring stations. The results showed that the properties of saline soil in Western Jilin province changed regularly at the spatial and temporal scales. In the longitudinal profile, the water content, soluble salt content, and organic matter content in the soil vary greatly with the seasons at a depth range of 0–50 cm, while their changes below 50 cm are not significant. This is related to the influence depth of the external environment. Meanwhile, the content of sand is relatively stable in the depth direction, mostly between 5 and 15%, while the content of silt and clay fluctuates greatly, and there seems to be a mirror relationship between them. Along the N(W)–S(E) direction, the crystallization proportion of clay minerals gradually increases by about 28% because the relatively humid and hot climate is conducive to mineral crystallization. Over time, in the S(E) study area, the precipitation is relatively abundant, and the shallow soil is desalted due to leaching, resulting in high salt storage in the deep soil. However, in the N(W) study area, salt migrates upwards with water under the dominant effects of evaporation and freeze-thaw, leading to the accumulation of salt in shallow soil and a decrease in salt storage in deep soil. In addition, the saline soil in the study area has strong alkalinity, and the pH increases from 8.2 to 9.8 in the N(W)–S(E) direction. Overall, the soil salinization situation in Western Jilin is not optimistic.

Micro–composition evolution of the undisturbed saline soil undergoing different freeze–thaw cycles

The micro–composition of the soil is closely related to its engineering properties. In Northeast China, seasonal freezing and thawing can induce deterioration of the physicomechanical characteristics of saline soil, which can ultimately lead to engineering failures and geological disasters. To investigate the micro composition evolution including the microstructure and grain size distribution of saline soil under the influence of freeze–thaw cycles, mercury intrusion porosimetry (MIP) and laser particle size analysis (LPSA) were used to test undisturbed saline soil specimens undergoing different freeze–thaw cycles. The pore size distribution curves showed a double–peak shape and the grain size distribution curves showed a bidirectional change. Overall, the pores >0.4 μm increased while the pores smaller than 0.4 μm decreased with increasing freeze–thaw cycles. Moreover, the grain size distribution showed a different changing trend at a pore diameter of approximately 10 μm. During the whole freeze–thaw cycle process, the fragmentation of coarse particles (> 10 μm) and the aggregation of fine particles (< 10 μm) were evident, causing the transformation of different pore sizes, and the bidirectional change existed synchronously in the whole process. The freeze–thaw cycles for saline soil caused the lyotropic salt precipitation and dissolution and the ice volumetric expansion and ice segregation to change the grain size distribution leading to the evolution of pore distribution, ultimately changing the soil micro–composition and resulting in the change of macro engineering characteristics. The study is useful for understanding the change in the engineering properties of saline soil under freeze–thaw cycles from a microscale perspective.

Impact of Biochar as a Soil Conditioner to Improve the Soil Properties of Saline Soil and Productivity of Tomato

Biochar increases crop yield, soil reliability, and carbon sequestration. This study examined how biochar affected soil properties and tomato yield in saline soil. The experiment was conducted in areas surrounding Khulna Agricultural University and in farmers’ fields close to Khulna, Bangladesh. The experiment’s layout was a randomized complete block design (RCBD). Tomato cultivation with eight treatments and three replications used biochar with the recommended fertilizer dose (RFD). Using biochar in saline soil significantly influenced tomato growth and yield character. Days after planting, plant height was dramatically impacted by various biochar treatment levels. The height of tomato plants ranged from 65.38 to 46.37 cm, yielding 49.23 tons per hectare. The experiments used biochar treatments to grow more tomatoes than traditional fertilizers and a control treatment. Compared with control treatments, biochar also changed the properties of salty soil after it was harvested. The soil’s pH is 6.51 and its particle density is highest at 2.65. The control treatments had the highest EC value, which was 2800, and the biochar application treatments had the lowest EC values. At 100 s/cm, the EC value made the soil 0.6 ppt saltier in the control treatment without biochar, but adding biochar made the soil 0.1 ppt less salty. The percentages of carbon, nitrogen, and organic matter were also the highest that they had been (1.88%, 1.073%, and 2.58%, respectively). The phosphorus concentration in the soil was 19.47 g/g after harvesting. The majority of K and S values used to treat salty soils are interchangeable. Significant changes in tomato growth, yield, and soil properties occurred when biochar was combined with recommended fertilizer doses and applied to saline soil for tomato cultivation.