Alkali Soils Research Articles

Remediating petroleum hydrocarbons in highly saline–alkali soils using three native plant species

Phytoremediation of total petroleum hydrocarbons (TPHs) contamination is a process that uses the synergistic action of plants and rhizosphere microorganisms to degrade, absorb and stabilize pollutants in the soil, and has received increasing attention in recent years. However, this technology still has some challenges under certain conditions (e.g., highly alkaline and saline environments). The present study was selected three native plant species (alfalfa, tall fescue, and ryegrass) to remediate petroleum pollutants in greenhouse pot experiments. The results indicate that TPH contamination not only inhibited plant growth, soil chemical properties and soil fertility (i.e. lower plant biomass, chlorophyll, pH, and electrical conductivity), but also increased the malondialdehyde, glutathione, and antioxidant enzyme activities (catalase and polyphenol oxidase). Further, correlation analysis results illustrated that TPH removal was strongly positively correlated with chlorophyll, soil fertility, and total organic carbon, but was negatively correlated with dehydrogenase, polyphenol oxidase, pH, and electrical conductivity. The highest TPHs removal rate (74.13%) was exhibited by alfalfa, followed by tall fescue (61.79%) and ryegrass (57.28%). The degradation rates of short-chain alkanes and low rings polycyclic aromatic hydrocarbons (PAHs) were substantially higher than those of long-chain alkanes and high rings PAHs. The findings of this study provide valuable insights into petroleum decontamination strategies in the highly saline - alkali environments.

Groundwater level dynamic simulation and soil salinization prediction of the closed hydrogeological unit in the arid irrigation area

Abstract Aiming at problems such as inaccurate simulation of groundwater level in closed hydrogeological units, difficult quantitative prediction of soil salinization degree, and unclear water and salt migration, a three-dimensional simulation model of groundwater was established, and the development trend of groundwater level and soil salinization was predicted. The groundwater level simulation results are consistent with the changing trend of the observational data and the simulation model can be used to predict groundwater levels in closed hydrogeological units. When climate scenarios and human activity change are set as future scenarios, the average groundwater buried depth will continue to decrease in the next 10 years, the area with a groundwater buried depth of 0–5 m will exceed 50%, and even the groundwater will overflow to the surface. The change of soil salt content is predicted quantitatively and the salinization degree will develop from ‘saline–alkali soil’ and ‘mild saline–alkali soil’ to ‘medium saline–alkali soil’. The process of water and salt migration in three key hydrologic zones, namely ‘irrigation infiltration’, ‘solute migration’, and ‘water and salt accumulation’, is revealed in the closed hydrogeological unit. The research results can provide new ideas for the improvement of soil and water environment problems.

Analysis of the Effect of Modified Biochar on Saline–Alkali Soil Remediation and Crop Growth

To solve the problem of soil degradation in coastal saline–alkali land, three different types of biochar (rice straw biochar, magnetic biochar, and humic acid–magnetic biochar) were prepared to remedy the saline–alkali soil under different mixing ratios. The effects of biochar on the growth of crops in saline–alkali soil were explored through a pot experiment on Chinese cabbage. The experimental results showed that the soil leaching treatment combined with humic acid–magnetic biochar could effectively repair the coastal saline–alkali soil. After adding 5% humic acid–magnetic biochar, the content of soil organic matter was 33.95 g/kg, the water content was 13.85%, and the contents of available phosphorus and available potassium were 9.43 mg/kg and 29.51 mg/kg. After adding 5% humic acid–magnetic biochar, the plant height of Chinese cabbage was 9.16 ± 0.19 cm, and the plant germination rate reached 83.33 ± 5.54%. The incorporation of biochar could effectively increase the chlorophyll content and soluble protein content of pakchoi and reduce the soluble sugar content of pakchoi. The study analyzed the effect of different modified biochar on saline–alkali land restoration and crop growth and explored the action rule of hydrochloric acid magnetic biochar on saline–alkali land restoration, which has important practical value for improving coastal saline–alkali land.

Research Progress on Improvement of Saline Alkali Soil

Soil salinization is one of the most important issues threatening agricultural production, food security and sustainability in arid and semi-arid regions worldwide. The improvement and comprehensive utilization of saline alkali soil is of great significance for cultivating healthy soil, ensuring global food security and mitigating climate change. This paper summarized the research progress of saline alkali soil improvement technology, and described briefly the causes of saline-alkali land. Moreover, the physical, chemical and biological methods of saline-alkali land improvement were analyzed. The improvement characteristics and effects of different materials and technologies are described. And we proposed suggestions for future research and development of desalination materials and technologies to provide a useful reference for the research and development of efficient improvement technology of saline-alkali soil, and accelerate the improvement of saline-alkali land and improve the quality of cultivated land to a greater extent.

Interactive Effect of Irrigation Volume and Planting Density on Growth and Salt Uptake in Field-Grown Drip-Irrigated Suaeda salsa (L.) Pall.

Planting halophytes such as Suaeda salsa (L.) Pall. under drip irrigation is a viable solution for the remediation of saline soils. We conducted this study to investigate the effects of different irrigation volumes and planting densities on the growth and salt uptake of Suaeda salsa under drip irrigation. The plant was cultivated in a field using drip irrigation at various irrigation volumes (3000 m·hm-2 (W1), 3750 m·hm-2 (W2), and 4500 m·hm-2 (W3)) and planting densities (30 plants·m-2 (D1), 40 plants·m-2 (D2), 50 plants·m-2 (D3), and 60 plants·m-2 (D4)) to examine the effects on growth and salt uptake. The study revealed that the amount of irrigation, planting density, and interaction between the two significantly affected the growth characteristics of Suaeda salsa. The plant height, stem diameter, and canopy width increased simultaneously with an increase in the irrigation volume. However, with an increasing planting density and the same irrigation volume, the plant height first increased and then decreased, while the stem diameter and canopy width decreased simultaneously. The biomass of D1 was the highest with the W1 irrigation, while that of D2 and D3 were highest with the W2 and W3 irrigations. The amount of irrigation, planting density, and their interaction significantly affected the ability of Suaeda salsa to absorb salt. The salt uptake increased initially and then decreased with an increasing irrigation volume. At the same planting density, the salt uptake of Suaeda salsa with the W2 treatment was 5.67~23.76% and 6.40~27.10% higher than that with W1 and W3, respectively. Using the multiobjective spatial optimization method, the scientific and reasonable irrigation volume for planting Suaeda salsa in arid areas was determined to be 3276.78~3561.32 m3·hm-2, and the corresponding planting density was 34.29~43.27 plants·m-2. These data can be a theoretical basis for planting Suaeda salsa under drip irrigation to improve saline-alkali soils.

Progress of Euhalophyte Adaptation to Arid Areas to Remediate Salinized Soil

With the increasing shortage of water resources, the current management of saline–alkali lands in semi-arid and arid areas has gradually transformed from “flooding irrigation with drainage” in the past to the combination of controlling regional water and salt balance, phytoremediation, and comprehensive utilization of halophyte resources. However, soil salinization caused by natural and anthropogenic factors has still been a major global environmental problem, which changes the chemical and physical properties of soil, deteriorates the quality of underground water, and decreases biodiversity, contributing to the loss of soil productivity and the succession of the halotolerant species. Euhalophytes, as the materials for phytoremediation, have been confirmed to be effective species in improving saline–alkali soils. They can redistribute salts in soil profile through the interaction of their desalinization potential and irrigation water leaching, thereby preventing secondary salinization and improving soil productivity for long-term reclamation of saline soil. In this review, the adaptation mechanisms of euhalophytes to saline soils are generalized from the views of morphological, physiological, and molecular aspects and evaluated for their potential to remediate saline soil through salt removal and promoting leaching. Euhalophytes can not only sequestrate salts inside the central vacuole of cells to tolerate higher salt stress by means of organ succulence, ion compartmentalization, and osmotic adjustment but facilitate water infiltration and salts leaching through root–soil interaction. The root system’s mechanical penetration increases soil porosity, decreases soil density, as well as stabilizes soil aggregates. Moreover, the suitability of phytoremediation in arid situations with low precipitation and non-irrigation and some agricultural practices need to be taken into account to avoid salts returning to the soil as forms of litter and deep tillage altering salt distribution. Hence, euhalophytes planting in semi-arid and arid areas should be evaluated from their adaptation, desalinization, and prospective commercial values, such as foods, biofuels, and medical development to alleviate soil secondary salinization crisis and enhance the productivity of arable agricultural land.

Effects of the Salt-Tolerant Gramineous Forage Echinochloa frumentacea on Biological Improvement and Crop Productivity in Saline–Alkali Land on the Hetao Ningxia Plain in China

Biological improvement is a sustainable approach for saline–alkali land amelioration and utilization. Echinochloa frumentacea (Roxb.) link is a salt-tolerant gramineous forage, which plays an important role in improving saline–alkali land. The Hetao Ningxia Plain is located in the upper–middle reaches of the Yellow River with a large area of saline–alkali soil, where E. frumentacea has potential applications for improving saline–alkali land. Three experiments were conducted on saline–alkali land in Pingluo County, Ningxia, including soil-leaching experiments in pots as well as monoculture or intercropping experiments involving E. frumentacea in fields. The results showed that: (1) E. frumentacea had a strong leaching ability of Na+ and SO42− in saline–alkali soil. (2) The planting of E. frumentacea decreased soil pH and total salt; enhanced the available N, P and K; and increased plant height, stem thickness and yields compared with the control. (3) The diversity of soil bacteria and land use efficiency could be improved by the intercropping of E. frumentacea with legume forages. Overall, E. frumentacea is an important pioneer species of biological improvement for the sustainable utilization of secondary saline–alkali land produced by irrigation around the world.

A Salt-Tolerant Strain of Trichoderma longibrachiatum HL167 Is Effective in Alleviating Salt Stress, Promoting Plant Growth, and Managing Fusarium Wilt Disease in Cowpea

Salt stress is a constraint factor in agricultural production and restricts crops yield and quality. In this study, a salt-tolerant strain of Trichoderma longibrachiatum HL167 was obtained from 64 isolates showing significant salt tolerance and antagonistic activity to Fusarium oxysporum. T. longibrachiatum HL167 inhibited F. oxysporum at a rate of 68.08% in 200 mM NaCl, penetrated F. oxysporum under 200 mM NaCl, and eventually induced F. oxysporum hyphae breaking, according to electron microscope observations. In the pot experiment, pretreatment of cowpea seedlings with T. longibrachiatum HL167 reduced the accumulation level of ROS in tissues and the damage caused by salt stress. Furthermore, in the field experiment, it was discovered that treating cowpea with T. longibrachiatum HL167 before root inoculation with F. oxysporum can successfully prevent and control the development of cowpea Fusarium wilt, with the best control effect reaching 61.54%. Moreover, the application of HL 167 also improved the K+/Na+ ratio of cowpea, alleviated the ion toxicity of salt stress on cowpea, and HL167 was found to effectively colonize the cowpea roots. T. longibrachiatum HL167, which normally survives in saline-alkali environments and has the functions of disease prevention and plant growth promotion capabilities, has important research implications for improving the saline-alkali soil environment and for the sustainable development of green agriculture.

Water and salt replacement through soil salt leaching under brackish water conditions with subsurface pipe drainage

AbstractTo explore the improvement effect of subsurface drainage and brackish water on saline alkali soil, an orthogonal experimental design was used to conduct soil column experiments under nine parameter combinations of the depth of the buried subsurface pipe, irrigation amount and salinity of brackish water. A numerical model of soil water and salt movement was established, and the physical parameters of the soil were verified by using the software HYDRUS‐1D. The results indicated that the salinity of the brackish water only affected salt replacement. The salt replacement associated with subsurface drainage decreases with increasing water and salt replacement area at a constant irrigation volume. The salt replacement amount through subsurface pipe drainage increased with the irrigation amount in constant water and salt replacement areas. When the burial depths of the subsurface pipes were 140 and 160 cm and the irrigation amounts were >3180 and 3990 m3 ha−1, respectively, the salt discharge through the subsurface pipes was greater than the salt content carried by the brackish water, and the salt content of the soil in the root zone reached the critical salt tolerance value of cotton, which can simultaneously show that the soil salt content would not affect cotton growth.

Isolation and screening of phosphorus solubilizing bacteria from saline alkali soil and their potential for Pb pollution remediation.

The high pH and salinity of saline alkali soil not only seriously restrict the growth of crops, but also aggravate the pollution of heavy metals. The fixation of heavy metals and the regulation of pH by phosphorus solubilizing microorganisms may become a new way to repair heavy mental and improve saline alkali soil. In this study, a saline-alkali resistant bacteria (CZ-B1, CGMCC No: 1.19458) was screened from saline-alkali soil, and its tolerance to salt/alkali/lead stress was investigated by shaking flask experiment. The strain was identified as Bacillus amyloliquefaciens by morphology and 16S rRNA gene sequence analysis. The optimum growth temperature of CZ-B1 is about 35°C-40℃. The maximum salt stress and pH that it can tolerance are 100g/L and 9 respectively, and its tolerance to Pb2+ can reach 2000mg/L. The phosphorus release amount of CZ-B1 to Ca3(PO4)2 within 72h is 91.00-102.73mg/L. The phosphate solubilizing index in PVK agar medium and NBRIP agar medium are more than 2, which can be defined as phosphate solubilizing bacteria. Moreover, the dissolution of CZ-B1 to phosphorus is mainly attributed to tartaric acid, citric acid and succinic acid in inorganic medium. In addition, the removal rate of Pb2+ by CZ-B1 can reach 90.38% for 500mg/L. This study found that CZ-B1 can immobilize Pb through three biological mechanisms (organic acid, extracellular polymers and mineralization reaction). The release of succinic acid (10.97g/L) and citric acid (5.26g/L) may be the main mechanism to promote the mineralization reaction of CZ-B1 (phosphate and oxalate) and resistance to Pb stress. In addition, the high enrichment of Pb2+ by EPS can increase the rate of extracellular electron transfer and accelerate the mineralization of CZ-B1. The screening and domestication of saline-tolerant phosphorus-solubilizing bacteria not only help to remediate Pb contamination in saline soils, but also can provide P element for plant growth in saline soil.

Natural Regeneration of Morus alba in Robinia pseudoacacia Plantation and the Mechanism of Seed Germination and Early Seedling Growth Restriction in the Yellow River Delta

There is a wide range of naturally regenerated Morus alba in the declining Robinia pseudoacacia plantation of the Yellow River Delta. It is important to clarify the key mechanism of natural regeneration of M. alba for the transformation of declining R. pseudoacacia plantation. According to the death density of R. pseudoacacia, the plantation of R. pseudoacacia was divided into nondeclining, moderately declining, and severely declining forests. The structural characteristics of adult trees and seedlings of M. alba in different decline degrees forest were investigated. A pot experiment was conducted to study the seed germination and early seedling growth of M. alba in saline alkali soil and nonsaline alkali soil under different soil salt contents and light intensities. The results showed that the natural regeneration of M. alba was obviously affected by the decline of R. pseudoacacia plantation. With the increase of decline degree, M. alba density and seedling density first increased and then decreased, and were the highest in the medium decline plantation. Under full light intensity, the vigor index of M. alba seeds and the biomass of seedlings were significantly greater than those of 25% full light intensity. The germination rate and germination index under 1‰ soil salt content were significantly lower than those under 3‰, but the biomass of seedlings was on the contrary. The 1000-seed weight, seed germination, and seedling biomass of moderately declining R. pseudoacacia plantations were close to those of nonsaline alkali land, while significantly higher than those of nondeclining plantations, but the germination index of moderately declining R. pseudoacacia plantation was higher than that of nonsaline alkali land. Therefore, the germination ability of maternal trees in saline alkali land was higher than that in nonsaline alkali land under salt stress.

Effects of different amendments on aggregate stability and microbial communities of coastal saline–alkali soil in the Yellow River Delta

AbstractOrganic amendments have been widely used in coastal saline–alkali soil remediation; however, the mechanisms involved and the interactions between organic and inorganic amendments are still unclear. In this work, furfural residue (particulate; C/N ratio: 51.87; O‐alkyl C + di‐O‐alkyl C: 42.35%, aromatic C: 40.89%) and black liquor (dissolved; C/N ratio: 3.11; O‐alkyl C + di‐O‐alkyl C: 32.20%, aromatic C: 28.32%) were tested to examine their effects on chemical properties, water‐stable aggregate fractions, chemical compositions of solid‐state soil organic matter (SOM), gloaming‐related soil protein contents, and microbial communities of coastal saline–alkali soil under a 400‐day incubation experiment. Furthermore, organic amendments mixed with mineral amendment (4:1) were employed to explore the interactions between organic and inorganic amendments. Furfural residue had stronger and longer effects on soil macroaggregate stability (~240 days, intense) than black liquor (~15 days, weak), and mineral amendment addition had a positive effect on the stability of microaggregates. Our results revealed that qualities (primary form, C/N ratio, and chemical composition) of organic amendment which can change microbial communities by increasing soil C/N ratio and effective chemical compositions of solid‐state SOM, are the key factors in promoting the rapid formation and longer stability of coastal saline–alkali soil aggregates. Moreover, inorganic amendment addition can further improve the formation and stability of microaggregates rather than those of macroaggregates. This study provided a much‐needed technical basis for remediation of coastal saline–alkali soil.

Effects of green manure cultivation for aboveground carbon store and returning to the field to ameliorate soil quality in saline alkali soil

The utilization of saline-alkali land together with the consideration of the productive value (improving soil productivity) and ecological value (increasing carbon store ability) has rarely been reported. We conducted a field experiment to investigate the impact of green manure cultivation for aboveground carbon (C) store and then returning this to field to improve soil quality in saline alkali soil. The biomass in <italic>Lolium multiflorum</italic> cultivation treatment was significantly (<italic>P</italic> &lt; 0.05) higher than that of <italic>Medicago sativa</italic> and <italic>Brassica campestris</italic> cultivation. A similar tendency was observed in aboveground C store. Green manure cultivation resulted in largely different physicochemical properties at time of harvest. Returning the green manure to the field could significantly (<italic>P</italic> &lt; 0.001) improve soil fertility. Moreover, the soil fertility index of <italic>Lolium multiflorum</italic> treatment was significantly (<italic>P</italic> &lt; 0.05) enhanced by 55.56% and 33.33%, as compared with <italic>Medicago sativa</italic> and <italic>Brassica campestris</italic> treatments. Based on PLS-PM analysis, both fast-changing soil properties and biomass exhibited the greatest positive impacts (0.72 of the total effects) on soil fertility improvement after aboveground returning to the field. Our research provides evidence that <italic>Lolium multiflorum</italic> is the best potential variety to improve saline alkali soil fertility. Additionally, green manure cultivation in saline-alkali soil is an important way to store carbon in plants, then returning to the field is a feasible approach to improve saline alkali soil quality, which is beneficial for the green and sustainable development of saline-alkali agriculture.

Halomonas binhaiensis sp. nov., isolated from saline-alkali soil.

A Gram-stain-negative, aerobic and rod-shaped bacterium, strain Y2R2T, was isolated from a saline-alkali soil sample collected from Binhai New Area, Tianjin, PR China. Growth of strain Y2R2T was observed at 10-45 °C (optimum, 30 °C), at pH 6.0-11.0 (optimum, pH 9.0) and in the presence of 0-15 % (w/v) NaCl (optimum, 9.0 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain Y2R2T was affiliated with the genus Halomonas and showed the highest similarity to Halomonas huangheensis BJGMM-B45T (99.0%) and Halomonas cupida DSM 4740T (98.4%). The digital DNA-DNA hybridization and average nucleotide identity values of 21.0-22.8 % and 73.3-75.7 % with the closely related species H. huangheensis BJGMM-B45T, H. cupida DSM 4740T, H. ventosae AL12T, H. stenophila N12T and H. litopenaei SYSU ZJ2214T were lower than the threshold recommended for species discrimination.The major respiratory quinone of strain Y2R2T was Q-9 and the major cellular fatty acids consisted of C16 : 0, C19 : 0 cyclo ω8c and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The DNA G+C content of strain Y2R2T was 57.0 mol%. On the basis of this polyphasic taxonomic study, strain Y2R2T is considered to represent a novel species of the genus Halomonas, for which the name Halomonas binhaiensis sp. nov. is proposed. The type strain is Y2R2T (=CGMCC 1.16974T=KCTC 72578T).

Soil Chemical Properties Strongly Influence Distributions of Six Kalidium Species in Northwest China

The degrees of adaptive responses of different halophytes to saline–alkali soil vary substantially. Kalidium (Amaranthaceae), a genus comprised of six species of succulent euhalophytes with significantly differing distributions in China, provides ideal material for exploring the ecophysiological relationships involved in these variations. Thus, in a large-scale field survey in 2014–2018, samples of soil (at 20 cm depth intervals spanning 0 to 100 cm) and seeds were collected from areas where these six species are naturally distributed. Chemical properties of soils in the areas and germinability of the species’ seeds in media with 0–500 mM NaCl and 0–250 mM Na2SO4 were then analyzed to test effects of salinity-related factors on the species’ distributions. The pH of the soil samples mainly ranged between 8.5 and 10.5 and positively correlated with their mean total salt contents. Germination rates of all six species’ seeds were negatively correlated with concentrations of NaCl and Na2SO4 in the media, and their recovery germination rates in distilled water were high (&gt;74%). The results show that the species’ distributions and chemical properties of their saline soils are strongly correlated, notably the dominant cation at all sites is Na+, but the dominant anions at K. cuspidatum and K. caspicum sites are Cl− and SO42−, respectively. Species-associated variations in concentrations of Ca2+ were also detected. Thus, our results provide clear indications of major pedological determinants of the species’ geographic ranges and strong genotype-environment interactions among Kalidium species.

Responses of Phragmites australis to Nitrogen Addition along Salinity Gradients in Coastal Saline–Alkali Soil

Soil salinization and nitrogen (N) enrichment in saline–alkali soils resulting from human activities cause potential environmental pressure on Phragmites australis. However, the response of P. australis to N addition under different salt conditions remains unknown. This study examined the changes in soil properties and growth indices as well as their relationship to N addition through an in situ field experiment using three soil salinity levels with P. australis in the Yellow River Delta. The study showed that soil salinity levels significantly affected the effects of N addition on soil pH and water contents. N addition increased the soil NO3– contents and decreased soil available phosphorus (Avail. P) contents; however, soil salinity levels did not impact the effects of N addition on soil NO3− and Avail. P contents. N addition decreased the biomass of P. australis, since the decrease in the competitiveness for N sources changed the vegetation diversity. The results suggest that the biomass, plant height, and leaf soil plant analysis development (SPAD) values of P. australis increased with increasing soil Avail. P contents rather than soil NO3– contents. Therefore, we suggest the important role of Avail. P addition in N enrichment conditions in saline–alkali wasteland and estuarine wetland ecosystems.

Changes in yield of tomato irrigated with salty water varied by soil properties and irrigation practices: A meta-analysis

ABSTRACT It has been extensively investigated whether salt water can be used as an alternative water resource for irrigation in tomato production due to the increasing freshwater scarcity. Changes in tomato yield under salt water irrigation were variable, ranging from −96.8% to 36.2%. Thus, a meta-analysis was performed by collecting 988 paired comparisons from 69 articles to draw a quantitative summarization that there was a significant negative effect of salt water irrigation on tomato yield with a grand mean decrease of 27.8%. Compared to the control, tomato yield significantly reduced by 39.0% on average following saline water irrigation (SI), significantly higher than that under brackish water irrigation (BI). Medium soil is the most suitable place to apply salt water for irrigation. BI performed best in alkali soil, while following SI higher tomato yield was obtained in non-alkali soil. There was a trend whereby decreased soil bulk density and soil salinity led to smaller reduction in tomato yield regardless of irrigation water salinity. Applying local irrigation or discontinuous irrigation was more possible to achieve higher tomato yield under salt water irrigation. These findings can provide a reference for developing rational salt water irrigation policies in tomato production.

OsSAP6 Positively Regulates Soda Saline–Alkaline Stress Tolerance in Rice

BackgroundSoil salinization is a worldwide environmental problem, especially in the arid and semiarid regions of northeastern China, which are heavily affected by soda saline–alkaline stress. At present, there is an urgent need to improve the soda saline–alkaline stress tolerance of rice.ResultsStress-associated proteins are involved in regulating the abiotic stresses in plants. There are 18 members of the rice stress-associated protein (OsSAP) gene family. In this study, the expression levels of OsSAP6 in leaves and roots were upregulated with increasing NaHCO3 stress duration. OsSAP6 was located in nucleus and cytoplasm. The bud length and total root length of OsSAP6 overexpression rice were significantly longer than those of Lj11 (Oryza sativa longjing11) during germination stage, and the survival rates, plant height and malondialdehyde content at the seedling stage showed tolerance growth of saline–alkaline stress. The expression of OsCu/Zn-SOD, OsAPX2, and OsCAT1 in transgenic lines was increased significantly under SAE (soda saline–alkali soil eluent) stress. OsSAP6 interacts with OsPK5 according to yeast two-hybrid screening and luciferase complementation experiments. The expression of OsPK5 increased under NaHCO3 and H2O2 stress, and the overexpression of OsPK5 in rice improved soda saline–alkaline tolerance.ConclusionOverexpression of OsSAP6 in rice significantly enhanced saline–alkaline tolerance compared with the wild type. It is speculated that OsSAP6 responds to soda salinity stress and interacts with OsPK5 to positively regulate soda saline–alkaline tolerance through ROS homeostasis. This study revealed the features of OsSAP6 involved in response to soda saline–alkaline stress and the interaction with OsPK5, which provided resources for breeding aimed at improving the soda saline–alkaline stress tolerance of rice.

Analysis of Alkali-Induced Soil Heaving in Non-Expansive Soil Using Electrokinetic Model

An attempt has been made in this paper to conduct an Electrokinetic (EK) enhanced large-scale model study to analyze the heaving phenomena observed in fields. The application of the EK technique on fields to study alkali-induced heaving has been simulated in the laboratory using a rectangular and circular model. The EK technique was mainly employed to facilitate alkali soil interaction. Analysis of the geometry of the model boundary on the various physiochemical as well as geotechnical properties of the soil was conducted. Before that, a simple heaving analysis was also performed in an oedometer without the EK technique. Compare to the maximum heaving of 5.55% observed in the oedometer the soil in EK-equipped circular and rectangular models showed the heaving of 5.42% and 4.21% respectively. The heaving pressure recorded for the oedometer was 67.5 t.m-2 while for the circular and rectangular models these values were 37.7 t.m-2 and 18.8 t.m-2 respectively. Further, the value of unconfined compressive strength of soil decreases from 141 kPa to 80 kPa after interaction with alkali and the decrease was more prominent in the circular EK model. However, there was an increase in the friction angle and a decrease in cohesion value after alkali interaction. The structural alteration due to alkali solution was examined by SEM and XRD analysis.

Impact of Biochar and Bioorganic Fertilizer on Rhizosphere Bacteria in Saline-Alkali Soil.

Biochar and bioorganic fertilizers (BOF) that are used in agriculture can, both directly and indirectly, impact rhizosphere soil microorganisms. However, changes to the halophyte rhizosphere bacterial community after applying biochar and BOF to saline-alkali soil have not been thoroughly described. This study has investigated the bacterial communities of halophytes in saline-alkali soil through the addition of different biochar and BOF formulas using Illumina-based sequencing of the 16S rRNA gene fragment. B_BOF (biochar and BOF combined application) had the best effect, either by promoting the plant growth or by improving the physical and chemical properties of the soil. The concentration of the rhizosphere bacterial communities correlated with the changes in soil organic matter (OM) and organic carbon (OC). Proteobacteria, Actinobacteria, Chloroflexi, and Acidobacteria accounted for &gt;80% of the total bacteria in each treatment. In addition, the abundance of Micromonospora was much higher in response to B_BOF than to the other treatments. BOF, with or without biochar, significantly influenced the bacterial community composition in the saline-alkali soil. The OC, OM, total nitrogen, and the available phosphorus had significant effects on the bacterial structure of this soil. The complex correlation of the bacterial communities between CK and B_BOF was higher compared to that between CK and FB or between CK and BOF. These findings suggested that the plant growth, the soil characteristics, and the diversity or community composition of the rhizosphere bacteria in saline-alkali soil were significantly influenced by B_BOF, followed by BOF, and then biochar; fine biochar had a stronger effect than medium or coarse biochar. This study provides an insight into the complex microbial compositions that emerge in response to biochar and BOF.