Soil Salinity Research Articles

RNA-Seq and WGCNA Analyses Reveal Key Regulatory Modules and Genes for Salt Tolerance in Cotton.

The problem of soil salinization has seriously hindered agricultural development. Cotton is a pioneering salinity-tolerant crop, so harvesting its key salinity-tolerant genes is important for improving crop salt tolerance. In this study, we analyzed changes in the transcriptome expression profiles of the salt-tolerant cultivar Lu Mian 28 (LM) and the salt-sensitive cultivar Zhong Mian Suo 12 (ZMS) after applying salt stress, and we constructed weighted gene co-expression networks (WGCNA). The results indicated that photosynthesis, amino acid biosynthesis, membrane lipid remodeling, autophagy, and ROS scavenging are key pathways in the salt stress response. Plant-pathogen interactions, plant hormone signal transduction, the mitogen-activated protein kinase (MAPK) signaling pathway, and carotenoid biosynthesis are the regulatory networks associated with these metabolic pathways that confer cotton salt tolerance. The gene-weighted co-expression network was used to screen four modules closely related to traits, identifying 114 transcription factors, including WRKYs, ERFs, NACs, bHLHs, bZIPs, and MYBs, and 11 hub genes. This study provides a reference for acquiring salt-tolerant cotton and abundant genetic resources for molecular breeding.

Assessing the Efficacy of Cyanobacterial Strains as Oryza sativa Growth Biostimulants in Saline Environments.

Soil salinity, which affects plant photosynthesis mechanisms, significantly limits plant productivity. Soil microorganisms, including cyanobacteria, can synthesize various exometabolites that contribute to plant growth and development in several ways. These microorganisms can increase plant tolerance to salt stress by secreting various phytoprotectants; therefore, it is highly relevant to study soil microorganisms adapted to high salinity and investigate their potential to increase plant resistance to salt stress. This study evaluated the antioxidant activity of four cyanobacterial strains: Spirulina platensis Calu-532, Nostoc sp. J-14, Trichormus variabilis K-31, and Oscillatoria brevis SH-12. Among these, Nostoc sp. J-14 presented the highest antioxidant activity. Their growth-stimulating effects under saline conditions were also assessed under laboratory conditions. These results indicate that Nostoc sp. J-14 and T. variabilis K-31 show significant promise in mitigating the harmful effects of salinity on plant size and weight. Both strains notably enhanced the growth of Oryza sativa plants under saline conditions, suggesting their potential as biostimulants to improve crop productivity in saline environments. This research underscores the importance of understanding the mechanisms by which cyanobacteria increase plant tolerance to salt stress, paving the way for sustainable agricultural practices in saline areas.

Effect of Nano-Zinc Oxide, Rice Straw Compost, and Gypsum on Wheat (Triticum aestivum L.) Yield and Soil Quality in Saline-Sodic Soil.

The salinity and alkalinity of soils are two fundamental factors that limit plant growth and productivity. For that reason, a field study conducted at Sakha Agric. Res. Station in Egypt during the 2022-2023 winter season aimed to assess the impact of gypsum (G), compost (C), and zinc foliar application in two images, traditional (Z1 as ZnSO4) and nanoform (Z2 as N-ZnO), on alleviating the saline-sodic conditions of the soil and its impact on wheat productivity. The results showed that the combination of gypsum, compost, and N-ZnO foliar spray (G + C + Z2) decreased the soil electrical conductivity (EC), sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP) by 14.81%, 40.60%, and 35.10%, respectively. Additionally, compared to the control, the G + C + Z2 treatment showed improved nutrient content and uptake as well as superior wheat biomass parameters, such as the highest grain yield (7.07 Mg ha-1), plant height (98.0 cm), 1000-grain weight (57.03 g), and straw yield (9.93 Mg ha-1). Interestingly, foliar application of N-ZnO was more effective than ZnSO4 in promoting wheat productivity. Principal component analysis highlighted a negative correlation between increased grain yield and the soil EC and SAR, whereas the soil organic matter (OM), infiltration rate (IR), and plant nutrient content were found to be positively correlated. Furthermore, employing the k-nearest neighbors technique, it was predicted that the wheat grain yield would rise to 7.25 t ha-1 under certain soil parameters, such as EC (5.54 dS m-1), ESP (10.02%), OM (1.41%), bulk density (1.30 g cm-3), infiltration rate (1.15 cm h-1), and SAR (7.80%). These results demonstrate how adding compost and gypsum to foliar N-ZnO can improve the soil quality, increase the wheat yield, and improve the nutrient uptake, all of which can support sustainable agriculture.

Cultivating sustainability: a multi-assessment of groundwater quality and irrigation suitability in the arid agricultural district of Dzira (Ksour Mountains, Algeria).

Groundwater serves a range of essential functions such as supplying drinking water, facilitating agricultural practices, and supporting industrial processes. This study examines with multiple methods the quality of groundwater in the agricultural region of Dzira, Algeria. By collecting 38 groundwater samples of different wells and boreholes, valuable awareness of the aptness of groundwater for irrigation in this arid landscape was gained. Most wells met Food and Agriculture Organization (FAO) criteria for the total dissolved solids (TDS) and the potential of hydrogen pH, but some areas had higher mineral content and electrical conductivity. Results show significant TDS variations, with 10.81% of wells exceeding limits and acceptable pH levels. Elevated EC values in 67.57% of wells show high salinity, affecting soil and plant growth. Major ions such as Mg2+ and SO4- exceeded FAO standards in 43.24% and 64.86% of wells, respectively, highlighting substantial mineral content in the groundwater. Suitability indices reveal that most wells pose low sodium hazards and are generally suitable for irrigation, though some areas face moderate to high restrictions. The irrigation water quality index (IWQI) ranged from 45.36 to 96.30, averaging 80.77, with 54.04% classified as "low restriction," suitable for sandy soils with good permeability but requiring caution on salt-sensitive soils. Hydrogeochemical analysis using principal component analysis (PCA) and hierarchical cluster analysis (HCA) identifies rapid evaporite dissolution from Triassic saline formations, with a correlation matrix showing associations between TDS and Ca2⁺, Mg2⁺, Na⁺, Cl⁻, and SO₄2⁻. This mineralization is likely from gypsum and halite. Zoning maps based on IWQI and other parameters depicted spatial variations in groundwater quality, guiding effective irrigation management strategies. Overall, the study underscores the importance of comprehensive water quality assessment for sustainable agriculture and emphasizes the need for targeted interventions to mitigate potential challenges associated with soil salinity and sodicity. Therefore, these findings can be useful to decision-makers and stakeholders in order to optimize water use and protect this vital resource.

The Comparative Effects of Phosphorus-Enriched Organomineral Fertilization on Some Chemical Properties of Calcareous Soils

ABSTRACT Phosphorus is a very important plant nutrient for the development of plants and its production is not unlimited in the world. In addition, excessive use can lead to soil and water pollution. In this respect, phosphorus should be used effectively in plant production, especially in calcareous soils. The aim of this study was to comparatively determine the effects of phosphorus-enriched organomineral fertilization (p-OMF), chemical phosphorus fertilization (CF), and organic fertilization (OF) on some chemical properties of a calcareous soil. The experiment was established in Söke county of Aydın province in the Southwest of Türkiye. In this study, four doses of dairy manure (DM1: 10, DM2: 20, DM3:30, and DM4: 40 t ha−1) in OF, four phosphorus doses (P1: 10, P2: 20, P3:30, and P4: 40 kg P ha−1) in the CF system, and sixteen different doses of OMF formed by the combinations of these two fertilizers were applied excluding control. According to the main research findings, p-OMFs increased the soil organic matter (SOM), salinity, total nitrogen (N), available phosphorus (P), and potassium (K) by 60.1%, 20.9%, 22.1%, 140%, and 17.2%, respectively. They also decreased soil pH by 4%. As a result, it was determined that the most effective organomineral fertilizer combination that maintains soil properties at appropriate levels in calcareous soils is DM3+P2 (30 t ha−1 dairy manure +20 kg P ha−1).

Soil Organic Matter and Bulk Density: Driving Factors in the Vegetation-Mediated Restoration of Coastal Saline Lands in North China

Coastal saline soils are an important soil resource that, when restored, can enhance arable land and preserve the natural ecology. With the aim of improving the use of coastal saline soils, we conducted a spot survey at Bohai coastal saline land to investigate the differences in soil properties between different vegetation types. The soil physical and chemical properties of various vegetation types, including Aeluropus sinensis, Imperata cylindrica, Tamarix chinensis, Lycium chinense, Hibiscus moscheutos, Helianthus annuus, Gossypium hirsutum, and Zea mays, were examined at two depth layers: 0–20 cm and 20–40 cm, and in two seasons, spring and autumn. The soil properties were compared with bare land as a control. The results indicated that the electrical conductivity, total soil salt content, sodium adsorption ratio, and bulk density of soils with vegetation cover were lower than those with bare land. On the other hand, soil pH, organic matter content, mean weight diameter, and saturated hydraulic conductivity were higher. The redundancy analysis results revealed a substantial positive correlation between soil pH, saturated hydraulic conductivity, water content, mean weight diameter, and organic matter content, as well as a significant positive correlation between soil electrical conductivity, total soil salt content, sodium adsorption ratio, and bulk density. Soil pH, saturated hydraulic conductivity, water content, mean weight diameter, organic matter content, and soil electrical conductivity, total soil salt content, sodium adsorption ratio, and bulk density were negatively correlated. The results of the structural equation model and variance decomposition showed that soil organic matter and bulk density were the key factors affecting the degree of soil salinization, and compared with their independent effects, their combined effect on soil salinization was greater. This study’s conclusions can provide a point of reference for further research on the mechanisms of soil improvement and desalinization in coastal saline land.

Arabinosylation of cell wall extensin is required for the directional response to salinity in roots.

Soil salinity is a major contributor to crop yield losses. To improve our understanding of root responses to salinity, we developed and exploited a real-time salt-induced tilting assay. This assay follows root growth upon both gravitropic and salt challenges, revealing that root bending upon tilting is modulated by Na+ ions, but not by osmotic stress. Next, we measured this salt-specific response in 345 natural Arabidopsis (Arabidopsis thaliana) accessions and discovered a genetic locus, encoding the cell wall-modifying enzyme EXTENSIN ARABINOSE DEFICIENT TRANSFERASE (ExAD) that is associated with root bending in the presence of NaCl (hereafter salt). Extensins are a class of structural cell wall glycoproteins known as hydroxyproline (Hyp)-rich glycoproteins, which are posttranslationally modified by O-glycosylation, mostly involving Hyp-arabinosylation. We show that salt-induced ExAD-dependent Hyp-arabinosylation influences root bending responses and cell wall thickness. Roots of exad1 mutant seedlings, which lack Hyp-arabinosylation of extensin, displayed increased thickness of root epidermal cell walls and greater cell wall porosity. They also showed altered gravitropic root bending in salt conditions and a reduced salt-avoidance response. Our results suggest that extensin modification via Hyp-arabinosylation is a unique salt-specific cellular process required for the directional response of roots exposed to salinity.

Potassium indole-3-butyric acid affects rice's adaptability to salt stress by regulating carbon metabolism, transcription factor genes expression, and biosynthesis of secondary metabolites.

Soil salinity pollution is increasing worldwide, seriously affecting plant growth and crop production. Existing reports on how potassium indole-3-butyric acid (IBAK) regulates rice salt stress adaptation by affecting rice carbon metabolism, transcription factor (TF) genes expression, and biosynthesis of secondary metabolites still have limitations. In this study, an IBAK solution at 40 mg L-1 was sprayed on rice leaves at the seedling stage. The results showed that the IBAK application could promote shoot and root growth, decrease sucrose and fructose content, increase starch content, and enhance acid invertase (AI) and neutral invertase (NI) activity under salt stress, indicating altered carbon allocation. Furthermore, the expression of TF genes belonging to the ethylene responsive factor (ERF), WRKY, and basic helix-loop-helix (bHLH) families was influenced by IBAK. Many key genes (OsSSIIc, OsSHM1, and OsPPDKB) and metabolites (2-oxoglutaric acid, fumaric acid, and succinic acid) were upregulated in the carbon metabolism pathway. In addition, this study highlighted the role of IBAK in regulating the biosynthesis of secondary metabolites pathway, potentially contributing to rice stress adaptability. The results of this study can provide new sustainable development solutions for agricultural production.

Application of Magnetized Ionized Water and Bacillus subtilis Improved Saline Soil Quality and Cotton Productivity.

Soil salinization, a significant global challenge, threatens sustainable development. This study explores the potential of magnetized ionized water irrigation and Bacillus subtilis application to mitigate this issue. The former method is hypothesized to enhance soil salt leaching, while the latter is expected to improve soil nutrient availability, thereby increasing microbial diversity. To address the unclear impact of these interventions on soil quality and cotton productivity, this study employs four different experimental methods: magnetized ionized water irrigation (M), application of 45 kg ha-1B. subtilis (B), a combination of 45 kg ha-1B. subtilis with magnetized ionized water irrigation (MB), and a control treatment with no intervention (CK). This study aims to clarify the effects of these treatments on soil bulk density (BD), field capacity (FC), salinity and alkalinity, nutrient content, microbial activity, and cotton crop yield and quality. Additionally, it aims to evaluate the efficacy of these methods in improving saline soil conditions by developing a soil quality index. The results showed that using magnetized ionized water for irrigation and applying B. subtilis, either alone or together, can effectively lower soil pH and salt levels, enhance microbial diversity and abundance, and improve the yield and quality of cotton. Notably, B. subtilis application significantly decreased BD and enhanced FC and nutrient content (p < 0.05). A correlation was found where soil nutrient content decreased as pH and salt content increased. Furthermore, a strong correlation was observed between the major soil bacteria and fungi with BD, FC, and salt content. Comparatively, M, B, and MB significantly boosted (p < 0.01) the soil quality index by 0.21, 0.52, and 0.69 units, respectively, and increased (p < 0.05) cotton yield by 5.7%, 14.8%, and 20.1% compared to CK. Therefore, this research offers eco-friendly and efficient methods to enhance cotton production capacity in saline soil.

Effects of Bacillus subtilis on cotton physiology and growth under water and salt stress

The scarcity of fresh water resources has severely limited agricultural production in arid areas. Although brackish water irrigation or fresh water deficit irrigation can alleviate the water resources crisis, both may cause water and salt stress to crop. Therefore, this study is based on the functional advantages of Bacillus subtilis in soil improvement and crop growth promotion to alleviate water and salt stress and build safe and efficient water-saving irrigation patterns. In this study, cotton (No. 50 Chuangmian) was selected as the research crop, and five application rates of Bacillus subtilis (0, 22.5, 45, 67.5 and 90 kg·ha−1) were combined with three irrigation patterns (brackish water, fresh water and fresh water deficit irrigations) to study the effects of Bacillus subtilis on soil moisture and salinity, soil microbial community, cotton physiology and growth under water and salt stress. The results showed that Bacillus subtilis could enhance soil water retention capacity, promote soil desalination, improve cotton growth indices (plant height, stem diameter, leaf area index, dry matter accumulation), and then increase yield and water use efficiency (WUE). Compared with the control treatment, the yield and WUE of Bacillus subtilis application treatments increased by 3.32–54.67 % and 1.68–41.07 %, respectively. In the cotton physiology characteristics, Bacillus subtilis increased proline content and the activity of superoxide dismutase, peroxidase and catalase while decreased malondialdehyde content in cotton leaves. Bacillus subtilis could enhance the relative abundance of bacteria with the functions of nitrogen fixation, stress resistance and biocontrol. A structural equation model proved that Bacillus subtilis could improve yield and WUE indirectly by directly improving soil microbial diversity, alleviating water and salt stress, and then improving cotton physiology and growth. According to a comprehensive evaluation of cotton physiology and growth, it was determined that the optimal improvement effect was achieved when the application rate of Bacillus subtilis was 45 kg ha−1; the synergistic effect of brackish water irrigation and Bacillus subtilis (45 kg·ha−1) was superior to that of fresh water deficit irrigation combining with Bacillus subtilis (45 kg·ha−1), which could be considered a priority strategy for alleviating the fresh water crisis in arid areas and promoting the efficient increase in cotton yield.

High spatiotemporal resolution vegetation index time series can facilitate enhanced remote sensing monitoring of soil salinization

High spatiotemporal resolution vegetation index time series can facilitate enhanced remote sensing monitoring of soil salinization

Study of the Impact of Drip Irrigation on Soil Salinization in the Al Haouz and Kelaa des Sraghna Region

Study of the Impact of Drip Irrigation on Soil Salinization in the Al Haouz and Kelaa des Sraghna Region

Molecular cloning and functional characterization in response to saline-alkali stress of the MhZEP gene in Arabidopsis thaliana.

Soil salinization is one of the major environmental factors that restrict plant growth and development. Zeaxanthin epoxidase (ZEP) functions in ABA biosynthesis and the xanthophyll cycle and has a vital role in plant responses to various environmental stresses. It was found by quantitative real-time PCR (qRT-PCR) that MhZEP responded to saline-alkali stress and showed the highest expression at 48h of saline-alkali stress, which was 14.53-fold of 0h. The MhZEP gene was cloned from the apple rootstock begonia (Malus halliana Koehne) and its protein physicochemical properties were analyzed. Subsequently, the functional characterization of MhZEP (ID: 103403091) was further investigated in Arabidopsis thaliana. The MhZEP contained a complete open reading frame with a length of 1998bp, and encoded 665 amino acids with an isoelectric point of 7.18. Phylogenetic tree analysis showed that MhZEP was the most homologous and closely related to Glycine max. Compared with wild-type, transgenic plants grew better under saline-alkali stress and the MhZEP-OE line showed higher chlorophyll content, carotenoid content, enzyme activities (POD, SOD, CAT and APX) and K+ content, whereas they had lower chlorosis and Na+ content than the wild type (WT), which indicated that they had strong resistance to stress. The expression levels of saline-alkali stress-related genes in A. thaliana MhZEP-OE were examined by qRT-PCR, and it was found that the MhZEP improved the tolerance of A. thaliana to saline-alkali stress tolerance by regulating the expression of carotenoid synthesis genes (MhPSY, MhZDS, MhLYCB and MhVDE) and ABA biosynthesis genes (MhNCED5, MhABI1 and MhCYP707A2). And the potassium-sodium ratio in the cytoplasm was increased to maintain ionic homeostasis by modulating the expression of Na+ transporter genes (MhCHX15 and MhSOS1) and K+ transporter genes (MhHKT1;1, MhNHX1 and MhSKOR1). Moreover, the expression of H+-ATPase genes (MhAHA2 and MhAHA8) was increased to reduce the oxidative damage caused by saline-alkali stress. In summary, MhZEP acted as an essential role in plant resistance to saline-alkali stress, which lays the foundation for further studies on its function in apple.

The adaptation of lichen symbiosis to desert saline-alkali stress depends more on their symbiotic algae.

Soil salinization is a major environmental threat to the entire terrestrial ecosystem. Lichens arose from the symbiosis of fungi and algae or cyanobacteria. They have a high tolerance to various extreme environments, including adaptation to saline-alkali habitats. Thus, lichens are pioneer species on saline-alkali soil. However, the separate resilience of the two symbiotic partners under saline-alkali conditions remains insufficiently understood. In this study, two representative symbiotic algae, Diplosphaera chodatii and Trebouxia jamesii, were studied for their physiological response to the saline-alkali stress by adjusting different concentrations of NaHCO3, together with their respective symbiotic fungi Endocarpon pusillum (terricolous lichen) and Umbilicaria muhlenbergii (saxicolous lichen). The results indicate that cell growth rate and biomass in all four cultures decreased in alkali-alkaline substrate, while cellular activities and ultrastructure were affected to a distinct extent. Compared with the symbiotic fungi, the algae were found to be more active in coordinating oxidative stress and lipid peroxidation damage under the saline-alkali stress. The antioxidant system of the alga was especially shown as a key adaptive trait and it provides an important strategy for species survival and persistence in arid saline-alkali desert. The specific survival ability of the lichen symbiosis relies on the stress resilience advantages of the symbiotic partners in combination. Our study provided new insights into understanding the adaptation of lichen symbiosis to desert saline-alkali soil, and the potential of lichen symbiotic algae in the future desert ecological restoration.

Integrated spatial priority assessment in Central Asia: Bridging biodiversity, ecosystem services, and human activities

Central Asia (CA) faces escalating threats from increasing temperatures, glacier retreat, biodiversity loss, unsustainable water use, terminal lake shrinkage, and soil salinization, all of which challenge the balance between ecological integrity and socio-economic development essential for achieving sustainable development goals. However, a comprehensive understanding of priority areas from a multi-dimensional perspective is lacking, hindering effective conservation and development strategies. To address this, we developed a comprehensive assessment framework with a tailored indicator system, enabling a spatial evaluation of CA's priority areas by integrating biodiversity, ecosystem services (ESs), and human activities. Combining zonation and geographical detectors, this approach facilitates spatial prioritization and examines ecological and socio-economic heterogeneity. Our findings reveal a heterogeneous distribution of priority areas across CA, with significant concentrations in eastern mountainous regions, river valleys, and oasis agricultural lands. We identified 184 key districts crucial for ecological and societal sustainability. Attribution analysis shows that natural factors like soil types, precipitation, and evapotranspiration significantly shape these areas, influencing human activities and the distribution of biodiversity and ESs. Multi-dimensional analysis indicates existing protected areas cover only 15% of the top 30% priority areas, revealing substantial conservation gaps. Additionally, a 38% overlap between ESs and human activities, along with 63.25% congruence in integrated areas, underscores significant human impacts on ecological systems and their dependency on ESs. Given CA's limited resources, it is crucial to implement measures that strengthen conservation efforts, align ecological preservation with socio-economic demands, and enhance resource efficiency through sustainable integrated land and water resource management.

Mitigation of soil salinity by addition of different rice straw biochar doses in salt-affected acid soil

The current study was carried out to evaluate the effect of rice straw biochar amendment and to identify the appropriate dose of biochar application to reduce soil acidity, salinity, toxicity, and sodicity in salt-affected acid soils. The rice straw biochar at 4 different rates of 0%, (control) 1%, 3%, and 5% (w/w) was mixed with 6 salt-affected acid soils: S1 (non-saline), S2 and S3 (low saline), and S4, S5, and S6 (moderate saline). The mixture was continuously shaken in distilled water for 7 days. The biochar application significantly increased soil pH and saturated electrical conductivity (ECe) with an increasing biochar application rate compared with the control. Significant decreases in sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) values below the critical level of sodicity were observed above the biochar application rate of 1%. Soluble chloride (Cl–) and soluble and exchangeable sodium (Na+) were significantly reduced above the biochar application rate of 1%. The biochar application (≥ 1%) led to a significant increase in soluble and exchangeable potassium (K+) and declines in soluble and exchangeable calcium (Ca2+) and magnesium (Mg2+). This study concluded that the biochar application rate of 1% was suitable for reducing soil acidity to a safe level for rice plants. The rice straw biochar application improved soil toxicity and sodicity by reducing soluble Cl– and soluble and exchangeable Na+, decreasing SAR and ESP. The biochar application also increased available K+, essential for rice plant growth and development in salt-affected soils.

Sodium Bicarbonate Tolerance During Seedling Stages of Maize (Zea mays L.) Lines

ABSTRACT(1) Soil alkalinization and salinization represent a growing global challenge. Maize (Zea mays L.), with its relatively low tolerance to salt and alkali, is increasingly vulnerable to saline‐alkali stress. Identifying maize genotypes that can withstand salinity and alkalinity is crucial to broaden the base of salt‐alkali‐tolerant maize germplasm. (2) In this study, we screened 65 maize germplasm resources for alkali stress using a 60 mM NaHCO3 solution. We measured fifteen morphological and physiological indices, including seedling height, stem thickness, and leaf area. Various analytical methods—correlation analysis, principal component analysis, subordinate function analysis, cluster analysis, stepwise discriminant analysis, and ridge regression analysis—were used to assess the seedling alkali tolerance of these maize germplasm resources. The physiological indices of six tested maize varieties were analyzed in greater detail. (3) The findings revealed complex correlations among traits, particularly strong negative associations between conductivity and root traits such as length, volume, surface area, diameter, and number of branches. The 15 evaluation indices were reduced to 7 principal components, explaining 77.89% of the variance. By applying affiliation functions and weights, we derived a comprehensive evaluation of maize seedling alkali tolerance. Notably, three germplasms—Liang Yu 99, Bi Xiang 638, and Gan Xin 2818—demonstrated significant comprehensive seedling alkali tolerance. Cluster analysis grouped the 65 maize germplasm resources into four distinct categories (I, II, III, and IV). The results of the cluster analysis were confirmed by multiclass stepwise discriminant analysis, which achieved a correct classification rate of 92.3% for 60 maize genotypes regarding alkalinity tolerance. Using principal component and ridge regression analyses, we formulated a regression equation for alkali tolerance: D‐value = −1.369 + 0.002 * relative root volume + 0.003 * relative number of root forks + 0.006 * relative chlorophyll SPAD + 0.005 * relative stem thickness + 0.005 * relative plant height + 0.001 * relative conductivity + 0.002 * relative dry weight of underground parts. Under sodium bicarbonate stress, morphological indices and germination rates were significantly reduced, germination was inhibited, photosynthetic pigment levels in maize leaves decreased to varying degrees, and the activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) significantly increased. Alkali stress markedly enhanced the antioxidant enzyme activities in maize varieties, with alkali‐resistant varieties exhibiting a greater increase in antioxidant enzyme activities than alkali‐sensitive varieties under such stress. (4) By screening for alkali tolerance in maize seedlings, the identified alkali‐tolerant genotypes can be further utilized as suitable donor parents, thereby enhancing the use of alkali‐tolerant germplasm resources and providing theoretical guidance for maize cultivation in saline‐alkaline environments.

Initial soil moisture and soil texture control the impact of storm surges in coastal forests

Flooding and salinization triggered by storm surges threaten the survival of coastal forests. The forest root zone (top 40 cm of soil) is the most affected by surge flooding. Determining the effect of a storm surge on edaphic conditions is essential to estimate vegetation response. Pre-storm soil hydrology could mitigate or enhance the salinization effect, ultimately determining the resilience of the forest. Here we assess the influence of pre-storm soil water content and salinity on storm surge effects in coastal vegetated areas. A 1D model (HYDRUS-1D) is used to simulate saltwater infiltration from above through the unsaturated zone. Different water content and concentration scenarios, along with scenarios with variable storm surge salt concentration, storm surge height and storm surge flooding duration are considered. In soils characterized by silt and clay, the maximum salinized soil depth increases as water content increases, affecting the top 40 cm of soil, except for clay loam soil, for which only the top 20 cm are salinized. In sandy soils, the salinization process involves the entire soil column. The contribution of water content to salinization varies from 12 % to 30 % along the top 40 cm in fine soils. In fine soils, the storm-surge height also becomes relevant. A study case is presented to support the numerical results. Field data confirm that soil water content controls the salinization of the root zone in clay and silt soils. Overall, we conclude that the root zones of coastal forests with clay and silt soils and low water content are the most at risk during storm surges. These events have the potential to radically change edaphic conditions and affect ecosystems.

Combined application of gasification filter cake and Portulaca oleracea to promote soil quality and tomato yields under irrigation with brackish water

Brackish water (BW) irrigation may cause soil quality deterioration and thereby a decrease in crop yields. Here we examined the impacts of applying gasification filter cake (GFC), intercropping with Portulaca oleracea (PO), and their combination on soil quality, nutrient uptake by plants and tomato yields under BW irrigation. The treatments evaluated included (i) freshwater irrigation (Control), (ii) BW irrigation, (iii) GFC application under BW irrigation (BW + GFC), (iv) intercropping with PO under BW irrigation (BW + PO), and (v) the combined application of GFC and PO under BW irrigation (BW + PO + GFC). Overall, the use of BW for irrigation resulted in a decline in both soil quality (assessed by a soil quality index (SQI) integrating a wide range of key soil properties including salinity, nutrient availability and microbial activities) and crop yields. Nevertheless, when subjected to BW irrigation, the application of GFC successfully prevented soil salinity. Additionally, the intercropping of PO decreased the soil sodium adsorption ratio and improved the absorption of nutrients by plants. As a result, the BW + GFC + PO treatment generally showed higher tomato yield as compared to other BW-related treatments (i.e. BW, BW + GFC and BW + PO). Compared to BW, the BW + GFC + PO treatment had an average increase of 24.7% in the total fruit yield of four Cropping Seasons. Furthermore, the BW + GFC + PO treatment consistently exhibited the highest fruit quality index (FQI). Taken together, the combined application of GFC and PO is effective in promoting soil quality and crop yields under BW irrigation.

Significant effect of salinity on zinc adsorption on tropical coastal and floodplain soils

AbstractRising sea levels due to climate change are causing increased salinisation of low‐lying coastal and floodplain soils, and the impact of this process on the bioavailability of plant nutrients needs to be understood as mitigation strategies are adapted. Zinc (Zn) is an element of particular importance due to its function as a micronutrient for plants including rice and other staple foods. In the current study, our aim was to investigate the effects of salinisation on zinc adsorption onto soils representing at‐risk coastal and floodplain environments, addressing in particular our knowledge gap concerning the roles that solution chemistry and soil composition play. To this end, we conducted batch adsorption experiments in the laboratory and ran geochemical models in saline solutions up to 0.7 mol L−1 ion strength incorporating both (i) a multi surface model (MSM) for surface reactions containing three phases, that is iron hydroxides, organic matter and phyllosilicate clays, and (ii) aqueous‐phase complexation to dissolved organic and inorganic ligands. Surface reactions were modelled using the diffuse double layer model, the NICA–Donnan model and an ion exchange model using the Gaines–Thomas convention. We combined the experimentally determined mass composition of surface phases with generic modelling parameters taken from the literature. We first show that increasing salinity enhances the formation of aqueous Zn‐chloride complexes in the presence of dissolved organic matter and bicarbonate, thereby decreasing the availability of free Zn2+ and supressing the partitioning of zinc to the adsorbed phase. We demonstrate using batch adsorption experiments with a calcareous hydraquent and a tropaquept, that salinity decreases zinc adsorption strongly in the pH range between 3 and 6. Satisfactory agreement between experiments and model calculations was achieved with root‐mean‐square errors ranging for different salinities between 2.88% and 2.92% for the hydraquent and between 4.59% and 2.74% for the tropaquept soil. Model predictions of adsorption were slightly inferior at low salinity for the hydraquent soil and at high salinity for the tropaquept soil, pointing possibly to an incomplete geochemical model or to a need to parametrise surface adsorption models at higher ionic strengths. Present surface models have been largely parametrised at lower ionic strength. We lastly apply the MSM to examine zinc adsorption in five endoaquepts soils, representing soil series from Bangladesh. We show that increasing salinity decreases zinc adsorption to the soil organic matter and the clay fractions. We conclude from our findings that increased soil salinity due to rising sea levels and climate change will have a significant impact on zinc cycling and possibly other micronutrients in areas where coastal soils and floodplain soils overlap, such as deltas and estuaries. In particular, we predict a decrease in zinc adsorption in acidic to neutral soils. The availability of zinc for biouptake through the roots of crop plants including rice will be significantly disturbed following salinisation, most likely affecting crop production. Our study demonstrates the potential that geochemical modelling combined with experimental data has to improve our capability to assess the effects of salinity due to rising seawater levels in vulnerable regions of the world.