Alkali Soils Research Articles

Microbes with high–abundance attributes dominate the prokaryote communities of saline–alkali soil and construct more complex networks in the plant rhizosphere

Understanding the interactions between plants and microbes in terms of core and/or keystone taxa is of great importance for promoting salt tolerant of plants and comprehensive utilisation of saline–alkali lands. However, our knowledge about the dominant microbial categories and their response to plant growth is limited. Here, we distinguished the categories of core and keystone taxa by classifying the prokaryotic categories and conducting network analysis in saline–alkali lands. Moreover, we explored how these important taxa varied between the plant rhizosphere and bulk soils. Overall, six categories of prokaryotes were identified. Approximately one–tenth of the species with high–abundance attributes accounted for two–thirds of total prokaryotes. Moreover, network analysis showed that nearly all links among the nodes were positive; and the identified keystone taxa mainly belonged to categories with high–abundance attributes. Furthermore, in the rhizosphere, a decreasing trend in the correlations of microbial diversity indices and community compositions with the soil properties was observed compared with those in the bulk soil. However, more keystone taxa and complex modules were strongly correlated with changes in the soil properties. These results suggest that the plant rhizosphere can recruit keystone prokaryotes with high–abundance attributes by establishing a syntrophic association between the plant and keystone taxa, which subsequently construct a complex microbial network structure. Although the ecological functions of the targeted keystone taxa need to be confirmed, our findings provide a potential method for constructing a core artificial microbiome with multiple approaches, further helping to develop microbial strategies to ameliorate salt stress in plants in saline–alkali lands.

Affected of Ameliorated Alkaline Water and Soil Amendments on Exchangeable Cation, Macro and Micronutrients in Sodic Soil under Drip Irrigation

The Field experiment was carried out at Anbil Dharmalingam Agricultural College and Research Institute, Tiruchirappalli using cotton (RCH- 20) as a test crop to examine the effect of ameliorated alkali water and soil amendments on soil properties, growth, and yield of hybrid cotton in sodic soil under drip irrigation. In this experiment, Drip irrigation with gypsum treatment water and drip irrigation with spent wash treatment water were used as main-plots treatments. Soil application of gypsum @ 50 % GR (5.2 t ha-1) and one time soil application of distillery spent wash @ 5 lakh litter ha-1 were imposed as sub-plot treatments. The treatment without amendments both under main plot and sub plots were used as control. The experiment was carried out using a strip-plot design with four replications. The application of additives through irrigation water (or) soil considerably decreased the pH of post-harvest soil. The soil exchangeable Ca and Mg were found significant due to soil application of amendments only and value ranged from 8.51 to 9.35 and 5.03 to 5.20 Cmol (p+) kg -1 respectively. The soil available nutrients N, P and K were found significant, and value range from 167 to 311, 15.4 to 21.5, 158 to 928 kg ha-1 respectively. The application distillery spent wash (DSW) and gypsum slightly increased the micronutrient cations range which from 4.80 to 6.85 mg kg-1 of Fe, 8.60 to 10.43 mg kg-1 of Mn, 0.64 to 0.88 of mg kg-1 of Zn, 1.10 to 1.42 mg kg-1 of Cu. The results of the field experiment revealed that application of amended alkali water and amended soil significantly increased all the growth and yield parameters of cotton. An increase in seed cotton yield of 701 and 544 kg ha-1 was recorded due to the application of gypsum treated water and DSW treated water respectively over control. Similarly, an increase of 773 and 973 kg ha-1 of seed cotton yield was recorded due to soil application of gypsum and DSW respectively over control. While considering the interaction effect, soil application of DSW along with gypsum bed treated water found to be the best for getting higher seed cotton yield (3015 kg ha-1) when compared to other treatment combination.

Intercropping of Echinochloa frumentacea with Leguminous Forages Improves Hay Yields, Arbuscular Mycorrhizal Fungi Diversity, and Soil Enzyme Activities in Saline–Alkali Soil

Soil salinization is detrimental to crop growth, agricultural yields, and environmental protection. Echinochloa frumentacea (Roxb.) Link is a pioneer species for the alteration of saline–alkali lands. In this paper, we examined the effects of intercropping between E. frumentacea and leguminous forages on saline land improvement in the saline–alkali soil of the Hetao-Ningxia Plain, China. We found that intercropping increased the diversity and richness of the arbuscular mycorrhizal fungi (AMF) community in the rhizosphere soil of E. frumentacea. Glomus was the dominant genus in the saline–alkali soil of the Hetao-Ningxia Plain, where Glomeraceae, VTX00067, VTX000193, and VTX000165 were the dominant species. Intercropping improved the activities of soil urease, sucrase, alkaline phosphatase, and catalase. The hay yields of E. frumentacea were correlated positively with soil enzyme activities, Chao1 index, and ACE index, and negatively with total water-soluble salt content. Together, intercropping between E. frumentacea and leguminous forages enhances AMF diversity and soil enzyme activities, which provides an agricultural practice for improving sustainability of the agro-ecosystem in saline–alkali areas.

Wax bayberry is a suitable rootstock for Chinese red bayberry cultivated in saline-alkali soil

Wax bayberry or wax myrtle, Morella cerifera L., (MC) is a member of the Myricaceae family and belongs to the same genus as Chinese red bayberry (Morella rubra) (MR). It is an evergreen shrub native to Pennsylvania, USA, and is resistant to saline-alkali stress. China has a large area of saline-alkali soil in the south-eastern coastal regions, and this study aimed to evaluate the suitability of MR cv ‘Biqi’ grafting on MC for cultivation on saline soil. This MC rootstock tolerated stress in soil with high sodium, magnesium and calcium concentrations with no toxicity symptoms. Trees of cv ‘Biqi’ grafted on MC grew normally in saline-alkali soil, with dark green leaves, high chlorophyll content and healthy appearance, while the trees grafted on MR suffered severe chlorosis in saline alkali soil. The average fruit weight of the ‘Biqi’ cultivar grafted on MC in saline alkali soil steadily increased over the 2016–2018 period, and were larger in size and higher in sucrose and citric acid content than those on the MR rootstock grown in either coastal or mountainous areas. The bayberry grafted on MC rootstock also tended to flower and set fruit 1–2 years earlier than that grafted on MR rootstock. High compatibility between the scion (MR) and rootstock (MC) was observed in the microscopic section of the grafting interface. Thus, wax bayberry was considered an effective rootstock for the cultivation of red bayberry in saline-alkali soils.

Integration of Sentinel–1 and Landsat–8 data for identifying deformation risk of hydraulic engineering in seasonally frozen salinization regions

Hydraulic engineering has positive effects on agricultural production and soil desalination. However, freeze–thaw cycles can cause instability in canal slopes, emphasizing the need for effective deformation monitoring. Using Sentinel-1B data acquired from November 2017 to August 2019 and applying the small baseline subset (SBAS) InSAR method, two unstable canal segments with vertical deformation rates exceeding –40 mm/year were identified in Songyuan, Northeast China. The canal slopes uplifted in winter and experienced accelerated subsidence in spring, with the shady slope experiencing a deformation rate approximately 10 mm/year faster than the sunny slope. Further investigation, integrating Landsat–8 data collected from November 2017 to August 2019, revealed that the shady slope received less thermal radiation than the sunny slope, with an average annual temperature difference on the land surface of approximately 1 ℃. In winter, the saline–alkali soil particles formed a thick unfrozen water film, which, driven by temperature and soil–water gradients, migrated towards the freezing front, froze, and caused soil frost heave. The shady slope experienced longer freezing periods and deeper frozen depths, up to 240 cm, causing more unfrozen water migration and greater uplift deformation than the sunny slope. In spring, as temperature rose, the soil thawed from the surface downward. Notably, the shady slope thawed at a slower rate than the sunny slope, forming a frozen lens near a depth of 100 cm. Frozen lens acted as a barrier for meltwater infiltration, impeding the dissipation of pore water pressure, making the shady slope prone to surface landslides. The integration of multiple data sources is beneficial for identifying deformation risk in hydraulic engineering.

Mechanism of microbial regulation on methane metabolism in saline–alkali soils based on metagenomics analysis

Saline–alkali soils constitute a globally important carbon pool that plays a critical role in soil carbon dioxide (CO2) and methane (CH4) fluxes. However, the relative importance of microorganisms in the regulation of CH4 emissions under elevated salinity remains unclear. Here, we report the composition of CH4 production and oxidation microbial communities under five different salinity levels in the Yellow River Delta, China. This study also obtained the gene number of microbial CH4 metabolism via testing the soil metagenomes, and further investigated the key soil factors to determine the regulation mechanism. Spearman correlation analysis showed that the soil electrical conductivity, salt content, and Na+, and SO42− concentrations showed significantly negative correlations with the CO2 and CH4 emission rates, while the NO2−-N concentration and NO2−/NO3− ratio showed significantly positive correlations with the CO2 and CH4 emission rates. Metabolic pathway analysis showed that the mcrA gene for CH4 production was highest in low–salinity soils. By contrast, the relative abundances of the fwdA, ftr, mch, and mer genes related to the CO2 pathway increased significantly with rising salinity. Regarding CH4 oxidation processes, the relative abundances of the pmoA, mmoB, and mdh1 genes transferred from CH4 to formaldehyde decreased significantly from the control to the extreme–salinity plot. The greater abundance and rapid increase of methanotrophic bacteria compared with the lower abundance and slow increase in methanogenic archaea communities in saline–alkali soils may have increased CH4 oxidation and reduced CH4 production in this study. Only CO2 emissions positively affected CH4 emissions from low– to medium–salinity soils, while the diversities of CH4 production and oxidation jointly influenced CH4 emissions from medium– to extreme–salinity plots. Hence, future investigations will also explore more metabolic pathways for CH4 emissions from different types of saline–alkali lands and combine the key soil enzymes and regulated biotic or abiotic factors to enrich the CH4 metabolism pathway in saline–alkali soils.

Promotion of Growth of Alfalfa by Erwinia persicina Cp2 Exopolysaccharides under NaCl Stress

Soil salinity poses a significant challenge to plant growth and agricultural productivity. Research demonstrated the potential of exopolysaccharides (EPS) to enhance plant growth and improve resistance to abiotic stress. Nevertheless, the precise regulatory mechanism by which EPS mediates salt tolerance in alfalfa (Medicago sativa) remains largely unexplored. To investigate the protective effects of EPS from Erwinia persicina Cp2 in enhancing salt stress tolerance in alfalfa, a hydroponic experiment was conducted on the ‘Aohan’ cultivar of alfalfa, and changes in germination rate, biomass, chlorophyll content, electrolyte leakage (EL), hydrogen peroxide (H2O2), malondialdehyde (MDA), proline (Pro), soluble sugar (SS), soluble protein (SP), and activities of superoxide dismutase (SOD) and peroxidase (POD) were analyzed with and without Cp2 EPS under 75 mmol/L NaCl conditions. The results show that the exposure of alfalfa to salt conditions seriously inhibited its germination and growth. However, it is interesting that the application of Cp2 EPS greatly alleviated the damage of salt stress on alfalfa and promoted the germination of alfalfa as well as the root length, seedling length, fresh weight, and dry weight of the plants. In addition, the increases in MDA, H2O2 content, and EL rate caused by salt stress were inhibited after Cp2 EPS treatment, while chlorophyll, Pro, SP, and SS contents as well as SOD and CAT activities were increased. Therefore, Cp2 EPS can significantly alleviate the toxic effect of 75 mmol/L NaCl stress on alfalfa, and comprehensive analysis shows that 1.5 g/L Cp2 EPS had the best alleviating effect on alfalfa at this salt stress concentration. This study lays a practical and theoretical foundation for the development of biogenic agents used to alleviate the growth of alfalfa in saline alkali soil.

Soil P solubilization and plant growth promotion by a saline–alkali-tolerant P-solubilizing bacterium, Bacillus sp. DYS211

Abstract High total P content but insufficient available P in soil is an obstacle that restricts the efficient utilization of P in saline–alkali soil regions. Although saline–alkali resistant P-solubilizing bacteria (PSB) solubilize insoluble P, few studies have focused on their application in plant growth. We isolated a PSB strain, identified as Bacillus sp. DYS211, from bird droppings in saline–alkali regions and determined its growth characteristics and resistance to salt and alkalis. To investigate the effect of PSB on the germination and growth of plant seeds, we performed a potting experiment using Suaeda salsa with PSB added. The PSB strain grew rapidly in the first 12 h, and the solubilized P content from PSB reached a maximum of 258.22 mg L−1 at 48 h. Saline–alkali tolerance and P-solubilizing ability tests showed that Bacillus sp. DYS211 preferred to dissolve inorganic P, was halophilic, and had a good P-solubilizing effect at 1%–8% salinity (available P > 150 mg L−1). It exhibited good P solubilization abilities when glucose and sucrose were used as C sources or when ammonium sulfate, ammonium nitrate or yeast extract powder were used as N sources. In the growth promotion test, PSB increased seed germination, particularly under high-salinity stress, with a growth promotion of 8.33%. The PSB also improved the growth of S. salsa, including plant height and biomass (up to three times) under both saline and alkaline conditions, and the stem diameter increased under high-salinity stress. This strain demonstrates potential for vegetation restoration in saline–alkali regions.

Rationalizing mineral gypsum use through microbially enriched municipal solid waste compost for amelioration and regaining productivity potential of degraded alkali soils

Reclamation of alkali soils to harness their productivity potential is more complex due to the presence of excess sodium ions, poor hydraulic conductivity and infiltration rate, resulting in poor plant growth and crop productivity. Sodic soil reclamation using inorganic ameliorants like mineral gypsum or phosphogypsum is beyond the reach of small and marginal farmers having alkali soils because of their higher market prices and shortage of availability. Conjoint use of inorganic and organic amendments can be a pragmatic solution for improving soil physico-chemical and biological properties and sustaining crop productivity. Municipal solid waste compost (MSWC) available in abundant quantity if enriched with the efficient halophilic microbial consortium and used in conjunction with a reduced dose of gypsum can be a cost-effective approach for sustainable reclamation of alkali soils and harnessing their productivity potential. Hence, a field experiment was conducted on a high alkali soil (pH2 9.2 ± 0.10), electrical conductivity (EC) 1.14 ± 0.12 dS m−1, exchangeable sodium percentage 48 ± 2.50 and organic carbon (0.30%) was conducted during 2018–19 to 2020–21 to study the combined effect inorganic and organic (enriched municipal solid waste compost (EMSWC)) amendments on amelioration of alkali soils and sustaining productivity of rice–wheat cropping system. Application of gypsum @ 25% GR + enriched MSW compost @ 10 t ha−1 (T6) showed significant improvement in soil physico-chemical and biological properties over the sole application of organic (T3 and T4), inorganic (T2) and control (T1). A significant improvement in soil fertility status in terms of available nitrogen and micronutrients as well as CO3, HCO3, Cl, Ca and Mg content were recorded with the combined application of organic and inorganic soil amendments (T5 and T6) over the sole application of mineral gypsum. Soil microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP) improved significantly due to the application of EMSWC with gypsum over the application of gypsum only. Grain yield of rice and wheat increased significantly (P < 0.05) owing to the application of a reduced dose of gypsum (25% GR) and EMSWC @ 10 t ha−1 (T6) with values of 5.55 and 3.83 t ha−1, respectively over rest of the treatments. Three years economic analysis of the study revealed that treatments T6 and T5 gave the highest positive net return whereas it was lowest in treatment T1 and negative in treatment T2. The highest benefit-to-cost ratio (B:C) was obtained in treatments T6 and T5 which were significantly higher compared to the rest of the treatments.

Influence of Interlayer Soil on the Water Infiltration Characteristics of Heavy Saline–Alkali Soil in Southern Xinjiang

Interlayer soil is common in southern Xinjiang, because interlayer can reduce the infiltration rate of soil water. To simulate the interlayer soil in heavy saline–alkali cotton fields, this paper adopted a vertical one-dimensional infiltration test. T1 (315 mm), T2 (270 mm), and T3 (225 mm) and different interlayer positions (T5, 315 mm) and thicknesses of the interlayer (T6, 315 mm) with the same irrigation volume, as well as one perforation and sand filling treatment (T4, 315 mm), were set. The influence of different irrigation amounts, locations, and thicknesses of the interlayer and sand injection on water infiltration was analyzed. The analysis results showed that with the increase in irrigation amount, the water infiltration rate and the migration distance of the wet front increased, but did not penetrate to the bottom soil (90 cm). Under the same irrigation volume, the increase in interlayer thickness (T6) compared with the increase in interlayer position (T5), the change in soil moisture content in the upper and lower layers of the interlayer was greater, and the advance time of wetting front migration and cumulative infiltration were slightly higher. After tunneling and sand filling (T4), the infiltration rate of water was increased, the migration time of the wet front was reduced, and the profile water content of each soil layer was improved. The Kostiakov model could better simulate the water infiltration characteristics of interlayer soil with different profile configurations in heavily saline–alkali land. The results showed that in all of the treatments, only the wet front of the soil moisture reached 100 cm in the T4 treatment, and the maximum was only 87.8 cm in the other treatments, indicating that too little irrigation water or the upward movement and thickening of the interlayer were not conducive to water infiltration. For the interlayer soil area in the heavy saline–alkali land in southern Xinjiang, the appropriate irrigation water should be more than 315 mm. The treatment of drilling first and then filling sand can be used as a simple but effective measure to increase the water infiltration rate of the interlayer soil, and can thus be applied to the layered soil structure in the interlayer position of 60–80 cm.

Leaf Transcription Factor Family Analysis of Halophyte Glaux maritima under Salt Stress

The reduction of crop yield caused by soil salinization has become a global problem. Halophytes improve saline alkali soil, and the halophyte transcription factors that regulate salt stress are crucial for improving salt tolerance. In this study, 1466 transcription factors were identified by transcriptome sequencing analysis of Glaux maritima leaves after salt stress (0, 600, and 800 mM/L NaCl). Their genes were distributed across 57 transcription factor families. KEGG and GO analyses showed significant enrichment in 14 pathways, with a total of 54 functions annotated. Gene expression analysis showed 820 differentially expressed genes distributed in 11 transcription factor families, including ERF, bHLH, WRKY, and NAC, and 8 expression modules. KEGG analysis revealed four genes with significant positive regulation: ABF2 (Unigene0078257) in the ABA signaling pathway, EIN3 (Unigene0000457 and Unigene0012139), and EIL1 (Unigene0042139) involved in ethylene signal transduction, and two with negative regulation, MYC1/2 (Unigene0009899 and Unigene0027167) in the main regulator of Jasmonic acid signal transduction. Protein–protein interaction networks suggested ABF2 and MYC1/2 as important transcription factors regulating G. maritima salt tolerance. Overall, the salt-tolerant transcription factors discovered in this study provide genetic resources for plant salt tolerance inheritance, and lay a theoretical foundation for the study of the salt-tolerant molecular mechanism of the halophyte Glaux maritima.

Application of Desulphurized Gypsum with Straw to Improve Physicochemical Properties of Saline-alkali Land in Yellow River Delta

In order to explore the effect of combining straw and desulphurized gypsum on improving coastal saline-alkali soil, taking the alkaline saline soil in the Yellow River Delta as the research object, six treatments including the control (CK), desulphurized gypsum (DG), medium straw amount (MS), desulphurized gypsum+low straw amount (DGLS), desulphurized gypsum+medium straw amount (DGMS), and desulphurized gypsum+high straw amount (DGHS) were set up through a field location experiment. Combined with the aggregate classification method, the changes in bulk density, total porosity, pH, soluble salt content, microbial biomass carbon, dissolved organic carbon, new carbon, and aggregate organic carbon of coastal saline alkali soil under different treatments were compared. The results showed that the MS and DGHS treatments significantly reduced soil bulk density and increased soil total porosity, water content, and average weight diameter. The pH and exchange sodium percentage decreased significantly under all treatments, and there was no significant difference. DG treatment significantly reduced the soil sodium adsorption ratio. Compared with that in the MS treatment, the soil sodium adsorption ratio of DGLS, DGMS, and DGHS showed a further decreasing trend, with a decrease range of 57%-66%. Compared with MS, soil soluble Na+ decreased by 27.92%, 32.23%, and 20.15% under the DGLS, DGMS, and DGHS treatments, whereas the soil soluble Ca2+ and SO42- contents increased significantly. Compared with that in CK, all treatments could significantly reduce Cl- content, and there was no significant difference among all treatments. Compared with that in MS, microbial biomass carbon and dissolved organic carbon were significantly increased by 113% and 147% by DGMS and 22.81% and 28.24% by DGHS, respectively. The new carbon formation of DGLS, DGMS, and DGHS was 67%, 114%, and 175% higher than that of MS, respectively. The average size proportion of fine aggregates treated by DGLS, DGMS, and DGHS was 29.12% higher than that treated by MS. Straw returning and application of desulfurized gypsum increased the organic carbon content of coarse aggregates and fine aggregates in salinized soil. The average value of new carbon formation in coarse aggregates and fine aggregates treated by DGMS and DGHS was 233% and 142% higher than that treated by MS, respectively. Desulphurized gypsum applied to soil did not lead to soil heavy metal pollution, and the soil heavy metal content of different treatments was lower than the secondary standard of the soil environmental quality standard. These results can provide scientific basis for the improvement and utilization of coastal saline-alkali soil and the comprehensive utilization of industrial and agricultural wastes in the Yellow River Delta.

Effects of Biochar and Organic Additives on CO2 Emissions and the Microbial Community at Two Water Saturations in Saline–Alkaline Soil

The nutrient-limiting conditions in saline–alkali soil as well as the salinity and alkalinity stress are successfully alleviated by water management measures and the addition of organic matter. However, the impacts of these two strategies on the microbe-driven CO2 emissions in saline–alkaline soils are not yet clear. Therefore, a 150-day incubation experiment was conducted in this study to evaluate the short-term effects of water regulation and the addition of organic matter with different characteristics on CO2 emissions and microbial community characteristics in saline–alkali soils under non-flooding conditions. This study was conducted at two water saturations, i.e., 50% WFPS and 80% WFPS. In addition, five organic matter treatments were conducted: CK: control; N: urea; SN: Straw + urea; SNH: Straw + urea + microbial agent; and SNB: Straw + urea + biochar. The results demonstrated that compared with 50% WFPS, 80% WFPS significantly increased cumulative CO2 emission by 27.66%, but significantly decreased salt content and the fungal Chao1 and Shannon indices. The application of the biochar and microbial agent decreased the cumulative CO2 emissions of the SN treatment by 27.39% and 14.92%, respectively. When sufficient carbon supply is available, the decrease in fungal diversity may reduce CO2 emission. The findings demonstrated that SNH and SNB at 80% WFPS might decrease CO2 emissions under straw carbon intake as well as the loss of labile organic carbon (LOC). Additionally, these treatments can alleviate microbial stress caused by salinity, which has a favorable impact on enhancing carbon storage in salinity-affected dryland soils.

Exploration of the Regulatory Pathways and Key Genes Involved in the Response to Saline–Alkali Stress in Betula platyphylla via RNA-Seq Analysis

The pH of saline–alkali soil is high because of carbonate salts, and the deleterious effects of saline–alkali soil on the growth of plants are greater than those of saline soil. Few studies have examined the saline–alkali tolerance of Betula platyphylla at the molecular level. To clarify the regulatory mechanism underlying saline–alkali tolerance in B. platyphylla, RNA sequencing analysis of B. platyphylla seedlings treated with NaHCO3 was conducted. Differences in gene expression in the roots of B. platyphylla seedlings under saline–alkali stress (induced via NaHCO3) for 3 h and 6 h were characterized, and a total of 595 and 607 alkali stress-responsive genes were identified, respectively. Most differentially expressed genes were involved in stress, signal transduction, secondary metabolic process, regulation of jasmonic acid, and the abiotic stimulus signaling pathway. The single nucleotide polymorphism loci in the differentially expressed genes were associated with the alkaline-salt tolerance in birch germplasm. In addition, birch plants overexpressing WRKY70 and NAC9 were obtained using the A. tumefaciens-mediated transient transformation method, and these two genes were found to play key roles in saline–alkali tolerance. Additional study revealed that WRKY70 and NAC9 can increase resistance to saline–alkali stress by enhancing reactive oxygen species scavenging and inhibiting cell death in birch plants. The results of this study enhance our understanding of the saline–alkali stress tolerance of B. platyphylla at the molecular level, and provide several key genes that could be used in the breeding of birch plants in the future.

Improving Soil Properties by Sand Application in the Saline-Alkali Area of the Middle and Lower Reaches of the Yellow River, China

Excessive soil salinity is a problem that makes soil unusable for agriculture, and most current research focuses on either chemical supplements or water conservation measures. Nevertheless, more information is needed about how sand treatment affects soil quality. In this study, a field experiment assessed the effect of sand application and cropping year on soil properties in an arid and semi-arid saline-sodic agricultural ecosystem. We found that sand application significantly improved the saline–alkali soil’s physical (i.e., pH, EC, TSC, BD), chemical (i.e., OC, AN, AP), and enzyme activity (i.e., Amy, Ure, Alp, Cat) properties, and that soil AN, AP, as well as TSC, were the crucial factors affecting soil properties. Simultaneously, soil properties gradually improved along with increasing cropping years, although these increases gradually became small. Our findings highlight the potential of sand as a soil supplement to enhance soil quality and structure in semi-arid agricultural ecosystems, especially when considering the cost.

Impacts of Corn Straw Compost on Rice Growth and Soil Microflora under Saline–Alkali Stress

Saline–alkali soil seriously inhibits crop growth and yields and threatens the sustainable development of agriculture. Corn straw compost can alleviate saline–alkali stress and improve crop growth and development. In this study, we demonstrate that corn straw compost (CSC) improved soil physicochemical properties, e.g., decreased pH and electrical conductivity (EC), but increased soil nutrients, e.g., available nitrogen and phosphorus, and soluble organic carbon, as well as activities of sucrase and urease in saline–alkali soil. CSC affected the structure of water-stable aggregates (WSA) and the composition of soil microflora in saline–alkali soil. With the increase in the content of CSC, the abundances of some genera, e.g., Thermobacillus, Thermopolyspora, and Thermobispora, were significantly increased, suggesting that they play an important role in improving soil nutrient components and physicochemical properties, which subsequently improved plant growth and development. Consequently, the biomass and yields of rice grown in saline–alkali soil were greatly improved. In conclusion, CSC can improve saline–alkali soil activities and microbial communities, thus improving crop growth and yields. Our findings provide a theoretical basis for the sustainable development of modern agriculture.

The Effect of Lactobacillus planturum YQM48 Inoculation on the Quality and Microbial Community Structure of Alfalfa Silage Cultured in Saline-Alkali Soil

Alfalfa cultivated in salt–alkali soil was used for fermentation, to which an inoculum of Lactobacillus plantarum YQM48 was added, to assess its effect on the feed quality and the microbial community structure of the fermented silage. A control was included without inoculum. The nutritional components, fermentation quality, pH, and microbial community of the silage were measured after 30 and 60 days of anaerobic fermentation. The results showed that after 30 and 60 days of fermentation in the presence of the inoculum, the content of water-soluble carbohydrates, crude protein content, and dry matter were all significantly higher than those of the control silage, the pH and butyric acid content were lower, and the content of lactic acid and acetic acid were higher (p &lt; 0.05 for all). There was no significant difference in pH and butyric acid content between 30 and 60 days of fermentation in the presence of the inoculum (p &gt; 0.05), while the lactic acid and acetic acid contents were significantly lower in the 60-day silage compared to the 30-day silage (p &lt; 0.05). Fermentation reduced the abundance of Cyanobacteria and Proteobacteria (the abundant phyla in the fresh alfalfa), while the abundance of Firmicutes increased, reaching 92.3% after 60 days of fermentation with inoculum. The dominant genus in that sample was Lactobacillus (70.0%), followed by Enterococcus (12.9%), while fermentation of 60 days without inoculum resulted in only 29.2% Lactobacillus, together with 27.8% Cyanobacteria, and 12.2% Enterococcus. In summary, the addition of L. plantarum YQM48 can improve the nutritional components and fermentation quality of alfalfa silage cultivated on a salt-alkali soil.

Amendment of Saline–Alkaline Soil with Flue-Gas Desulfurization Gypsum in the Yinchuan Plain, Northwest China

The effective and safe use of FGD gypsum in agricultural land is still debated in some countries even though its effectiveness in soil management has been reported in many studies. Thus, the changes in the levels of soil salinity, alkalinity, crop yield, and other physicochemical properties in different soil types and crops after reclamation and planting with FGD gypsum over four years are evaluated in this paper. The main aim of this paper is to review the effects of six treatment technologies in addressing soil salinity and sodicity and crop production in soils, with a focus on the basic theory, key technologies, and industrialized applications. This paper also shows that soil conditions can be improved and crop yields can be increased by using FGD alone or in combination with humic acid or fertilizer. FGD gypsum plus K–Zn–Mn fertilizer increased the yield of rice by 135%. In alkaline, salinized, and secondary salinized soils, FGD gypsum combined with organic fertilizer or organic plus chemical fertilizer increased the yield of rice by 21.2% and 60.4%, the yield of sunflower by 2.4% and 23.6%, and the yield of medlar by 18.81% and 20.78%, respectively. The application of FGD gypsum also increased the salt tolerance of salt-tolerant plants. Combined with drainage, laser field levelling and tillage decreased soil salinity by more than 63.76% and increased the yield of oil sunflower by up to 96.96%. This study provides convincing evidence of the benefits of the application of the six treatments to reclaim saline–alkali soils. It is suggested that comprehensive measures should be taken to improve saline–alkaline soil.

Calcium-modified biochar rather than original biochar decreases salinization indexes of saline-alkaline soil.

We investigated the improvement effects of herbaceous (corn) and woody (oak sawdust) biochar with their calcium modification on saline alkali soil. The addition of unmodified biochar regardless of types had no significant effect on the soluble cations (Na+, Ca2+, and Mg2+) and the main indicators of soil salinity and alkalinity (pH, sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), and total alkalinity (TA)), but the addition of calcium modified biochar decreased these soluble cations and indicators, especially the addition of modified woody biochar (PBM). Compared to CK, TA decreased by 70.02% and 89.25% in PBM with 2% and 4% addition, respectively. Soil ESP and SAR showed a significantly positive correlation with pH and TA, which indicated that soil salinization and alkalization were synchronized. These results showed that the calcium modified biochar, especially the modified woody biochar, instead of the original biochar could be potential soil amendments for the improvement of saline-alkali soil.

Analysis of the pore structure characteristics of saline soil in the profile within the frozen depth

Soil pores play a critical role in the complex physical coupling process and are closely associated with the mechanism of soil salinization. This research used mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and laser particle size analysis on a soil profile about 230 cm deep in Qian'an, where soda saline–alkali soil is distributed and the deepest underground freezing depth is 180 cm. The material composition of the soil in active layer was identified, and the soil pores were classified as micropores (<0.04 μm), small pores (0.04–0.4 μm), mesopores (0.4–4 μm), and macropores (>4 μm). The soil deposited at a depth of 0 to 80 cm was affected by freeze–thaw cycles and dry–wet cycles, developing longitudinal cracks. During the rainy season, clay particles and salt were carried downward by rainfall, whereas at a depth of 30 to 80 cm, the exchangeable sodium ions and clay particles in the soil created a thick diffused layer and hindered rainfall infiltration, resulting in salt accumulation. The small pore diameter and low porosity of the soil in this depth range caused pores degradation, further exacerbating the salinization process. The soil deposited at a depth of 80 to 120 cm had low clay content, resulting in limited upward migration of unfrozen water during freezing periods. Upon thawing, the salt and fine clay particles moved upward with capillary water, leading to a lower salt content than the upper soil. Additionally, this depth range had a high content of macropores with a large average pore diameter. The soil deposited at a depth of 120 to 180 cm had high clay content, and during short freezing periods, salt migrated upwards with unfrozen water along poorly connected longitudinal cracks with limited clay particle migration. The macropore content was low, and the average pore diameter was small due to clay particles filling the pores. The salt content in this depth range was lower than in the upper soil. The pore structure characteristics of the saline soil in the active layer provide insights into salt deposition mechanisms, and this research offers data support from a pore-scale perspective for preventing the salinization process.