Soil Salinity Research Articles

Optimization of leaching level and alternating drip irrigation start time improved water saving, yield enhancement, and salt leaching

Shortage of water resources and salinization of soil are two important factors restricting the sustainable development of agriculture in Xinjiang. The current drip irrigation strategy cannot meet the high efficiency water saving and salt leaching requirement, seriously limiting sustainable development. Therefore, in 2020 and 2021, a field experiment was conducted with three leaching levels (120, 240 and 360 mm) and four alternate drip irrigation (ADI) start time (no ADI, seedling, budding and flowering). The field experiment was combined with HYDRUS to investigate the effect of water saving and salt leaching by combining ADI with leaching during the reproductive period. The results showed that the HYDRUS-2D model simulated soil moisture and salinity with high accuracy under different irrigation conditions, with R2 ranging from 0.63 to 0.93, MRE from 2.45 % to 11.66 %, and RMSE from 1.88 % to 4.41 % for soil moisture and 0.29 g kg−1 to 0.97 g kg−1 for soil salinity, respectively. Optimization of irrigation method, leaching level and ADI start time all improved water and salinity stress characteristics. Although initially high soil salinity resulted in the conversion of some severe stress to moderate due to the irrigation, these disadvantages were offset by reductions in severe stress duration and area. Water-salt production model constructed based on water and salt stress characteristics demonstrated good yield simulation performance. According to HYDRUS, water-salt production model and comprehensive evaluation, starting ADI at the 3rd irrigation event with a leaching level of 290 mm was found to be optimal considering yield, water use efficiency, soil desalination and desalination efficiency. Considering the practicability, the recommended optimum ADI leaching level was 262–318 mm, with ADI initiated between the 2nd and 4th irrigation event. The study provided a vital theoretical basis for efficient water-salt management, supporting sustainable development in saline-alkali cotton fields in Xinjiang under limited water resources.

Assessing the Effectiveness of Satellite and UAV-Based Remote Sensing for Delineating Alfalfa Management Zones Under Heterogeneous Rootzone Soil Salinity

Site-specific application of agricultural inputs is crucial for optimizing resource utilization in alfalfa (Medicago sativa L.) production and addressing challenges such as soil salinity. The main objective of this study was to assess the effectiveness of PlanetScope and UAV-based NDVI imagery for delineating alfalfa management zones under heterogeneous rootzone soil salinity. The research was conducted in the alfalfa field located in Imperial Valley, CA. The extent of rootzone soil salinity was assessed using Electromagnetic induction (EMI) technology and deep soil sampling. Reference management zones were then defined using the soil salinity (ECe) map derived from apparent electrical conductivity (ECa) data. Additionally, a time series of NDVI images from PlanetScope imagery and an NDVI image captured using an unmanned aerial vehicle were used to delineate remote sensing-based management zones. Laboratory analysis of disturbed soil samples collected at various depths provided soil physicochemical property data. Soil salinity of the samples ranged from 2.2 to 13.4 dS m−1 with a moderate level of variability (CV = 37.7%). ECe-based management zones accounted for approximately 83% of the field's variability and exhibited substantial differentiation among delineated zones concerning diverse soil properties, including ECa, ECe, gravimetric water content, Mg2+, boron, Ca2+, Na+, and Cl−. Notably, NDVI images effectively captured field variability on par with ECe-based zoning. Moreover, NDVI images recommended the same optimal number of zones (i.e., three) to address the field's variability, aligning with the ECe-based zoning approach. Our findings highlight that heterogeneity of soil salinity in the root zone primarily impacts the variability of alfalfa NDVI early in the growing season. Consequently, this early stage emerges as the most opportune timeframe for NDVI-based zoning for rapid assessment of rootzone soil salinity concerns.

Enhancing crop yield and microbial diversity in saline-affected paddy soil through biochar amendment under aquaculture wastewater irrigation

Biochar is frequently employed to ameliorate saline-affected paddy soil. However, there are controversial research findings regarding the applicability of biochar for the enhancement of soil physicochemical properties and agricultural (crop) yield, particularly under conditions of wastewater irrigation in agricultural production. This study investigates the effects of controlled soil salinity levels (1 ‰ and 3 ‰), induced using sodium chloride, and the targeted application of biochar in a pot experiment. The study examines the impact on physicochemical characteristics of different soil layers, physicochemical properties, and physiological responses of rice plants irrigated with aquaculture wastewater. It also delves into soil microbial diversity and the predominant bacterial species. The research findings reveal that biochar exerts a significant influence on soil properties and nitrogen content in saline environments. The addition of biochar enhanced soil electrical conductivity (EC), modulated the distribution of organic carbon, and altered nitrogen transformation processes within the soil. Consequently, biochar application resulted in a 14.2 % and 6.81 % increase in rice yield at 1 ‰ and 3 ‰ salinity levels, respectively. Furthermore, biochar increased leaf area by 25.3 % and 45.9 % in 1 ‰ and 3 ‰ salinity stress separately and enhanced the nitrogen content (TN) in leaves by 28.6 % when the soil salinity is 1 g/kg, demonstrating a positive impact on nitrogen uptake. Additionally, biochar has shown potential in mitigating nitrous oxide (N2O) emissions. Its addition led to a reduction in the relative abundance of Actinobacteria while increasing the relative abundance of Firmicutes. These findings provide novel insights into the transformative potential of biochar in improving the characteristics of saline paddy soil and augmenting rice yield when used in conjunction with aquaculture wastewater irrigation.

Leaf carbohydrate metabolic enzyme activities are associated with salt tolerance and yield stability in the climate-resilient crop Camelina sativa

Soil salinity is an increasingly severe problem affecting plant growth and development thus posing a threat to agricultural production worldwide. Many crops currently grown are susceptible to even moderate salt stress, and crop diversification is sought to cope with increasingly challenging environmental conditions. Camelina sativa is a versatile, underutilized, low-input Brassicaceae oilseed crop valued for its high-quality seeds and its resilience to a wide range of climate conditions. In this study, the effects of salt stress on the growth and productivity of two camelina cultivars and six landraces from different geographic regions were examined. The performance of these lines was related to adjustments in their carbohydrate metabolic enzyme activity profiles in leaves as a central physiological hub. Profiling enzyme activities and their regulation in response to salt stress revealed significant genotype × treatment (G × T) interactions and allowed the identification of specific activity signatures associated with differences in yield stability in the tested lines. Yield-stable landraces showed distinct regulation patterns contrasting those of less yield-stable lines. In particular, upregulation of specific enzyme activities was associated with yield stability under salt stress. Camelina landraces may be promising resources to improve tolerance to salinity, with plasticity in carbohydrate metabolism as a contributing mechanism. Overall, these results provide a valuable basis for enzyme activity signatures as new physiological markers for supporting breeding programmes.

Arbuscular mycorrhizal fungi and exogenous Ca2+ application synergistically enhance salt and alkali resistance in perennial ryegrass through diverse adaptive strategies

The challenge of soil salinization and alkalization, with its significant impact on crop productivity, has raised growing concerns with global population growth and enhanced environmental degradation. Although arbuscular mycorrhizal fungi (AMF) and calcium ions (Ca2+) are known to enhance plant resistance to stress, their combined effects on perennial ryegrass’ tolerance to salt and alkali stress and the underlying mechanisms remain poorly understood. This study aimed to elucidate the roles of AMF Rhizophagus irregularis and exogenous Ca2+ application in molecular and physiological responses to salt-alkali stress. AM symbiosis and exogenous Ca2+ application enhanced antioxidant enzyme activity and non-enzymatic components, promoting reactive oxygen species (ROS) scavenging and reducing lipid peroxidation while alleviating oxidative damage induced by salt-alkali stress. Furthermore, they enhanced osmotic balance by increasing soluble sugar content (Proportion of contribution of the osmotic adjustment were 34%~38% in shoots and 30%~37% in roots) under salt stress and organic acid content (Proportion of contribution of the osmotic adjustment were 32%~36% in shoots and 37%~42% in roots) under alkali stress. Changes in organic solute and inorganic cation-anion contents contributed to ion balance, while hormonal regulation played a role in these protective mechanisms. Moreover, the protective mechanisms involved activation of Ca2+-mediated signaling pathways, regulation of salt-alkali stress-related genes (including LpNHX1 and LpSOS1), increased ATPase activity, elevated ATP levels, enhanced Na+ extrusion, improved K+ absorption capacity, and a reduced Na+/K+ ratio, all contributing to the protection of photosynthetic pigments and the enhancement of photosynthetic efficiency. Ultimately, the combined application of exogenous Ca2+ and AMF synergistically alleviated the inhibitory effects of salt-alkali stress on perennial ryegrass growth. This finding suggested that exogenous Ca2+ may participate in the colonization of perennial ryegrass plants by R. irregularis, while AM symbiosis may activate Ca2+ pathways. Consequently, the combined treatment of AM and Ca2+ is beneficial for enhancing plant regulatory mechanisms and increasing crop yield under salt-alkali stress.

Temporal dynamics of soil salinization due to vertical and lateral saltwater intrusion at an onshore aquaculture farm

Temporal dynamics of soil salinization due to vertical and lateral saltwater intrusion at an onshore aquaculture farm

Differential effects of foliar and seed priming glycine betaine application on quinoa physiology under varying salinity level

Rising soil salinity hinders global crop yields by damaging plants, threatening food security. This study assessed glycine betaine (GB) application methods (foliar, seed priming) and salinity levels (0, 60, 120, 180 mM NaCl) on quinoa over two seasons. For ionic homeostasis, seed priming improved K+/Na+ ratio by 10–15 % at low salinity, while foliar was 12–18 % more effective at high salinity. Seed priming remained 10–15 % superior for roots. Foliar enhanced osmolytes by 12–16 % at low salinity, but seed priming had 16–20 % stronger effects at high salinity. Under low salinity, seed priming provided 8–12 % better protection for chlorophyll and photosynthetic efficiency. At high salinity, foliar GB was 10–15 % best for chlorophyll, seed priming 12–16 % more effective for photosynthetic rate, and foliar GB had an 8–10 % edge for Fv/Fm. GB reduced MDA by 8–12 % at low salinity, 12–16 % with seed priming at medium salinity in 2023, and 16–20 % with foliar in 2024. At high salinity, seed priming decreased MDA by 20–25 % in 2023, while foliar showed a 24–28 % reduction. GB moderately enhanced antioxidants by 8–12 % under mild stress, but seed priming and foliar differed 16–20 % in effectiveness under severe stress. For nutrients, seed priming had a 12–16 % advantage for nitrogen at medium salinity in 2023, while foliar excelled with a 16–20 % increase under high stress in 2024. Seed priming was 16–20 % better for phosphorus at high salinity in 2023, but foliar had 20–25 % superior results in 2024. These findings highlight complex plant responses to GB-salinity interactions, with optimal methods varying by trait, stress level, and environmental conditions.

Evaluation of Soils Affected by Salts in the Al-Jufra - Sokna Area

This study was conducted to assess the extent of the impact of natural, environmental and human factors on soil salinity and its distribution variation in the Al-Jufra region, specifically in the Al-Hamam Agricultural Project - Sokna, in addition to identifying the type of soil prevailing in the region. To achieve the objectives of this study, a series of laboratory experiments were conducted where samples were collected from the surface layer 0 - 30 cm and the subsurface layer 30 - 60 cm and were prepared and some physical and chemical properties were estimated, including pH, EC, CaCO3, O.M. CEC. After conducting the tests, it was noted that most of the soils in the study area have three different types of texture. The results of the chemical analysis showed a high electrical conductivity of the surface layer soil compared to the subsurface layer. On the other hand, the results showed high ESP values for most soils, as its value in the surface layer was higher than the lower layer of the soil. The study shows the role played by human factors in the increasing phenomenon of salinization of agricultural soils in the project area through mismanagement by leaving the land fallow after exploitation, and the lack of drains and the low efficiency of the existing ones.

Small Farmers’ Agricultural Practices and Adaptation Strategies to Perceived Soil Changes in the Lagoon of Venice, Italy

Farmers have a pivotal responsibility in soil conservation: they can either preserve or deplete it through their choices. The responsibility of agriculture increases when practised in delicate ecosystems, such as lagoonal ones. The Venetian Lagoon islands, which are increasingly subjected to natural and anthropic subsidence, occasional flooding events (acqua alta), and eustatic sea level rise, are constantly exposed to erosive processes that challenge farmers to play with their adaptive capability. This research was carried out on the islands of Sant’Erasmo and Vignole, the most representative of island agriculture in the Venetian Lagoon: they almost exclusively rely on agriculture, which is non-existent in the other islands. This empirical research aimed to explore farmers’ agricultural practices, perceptions of soil changes, and how they adapt to them. It was fundamental for this study that the field research involved direct human contact with farmers (through semi-structured interviews) for data collection and using qualitative methods for data analysis, integrating scientific and non-scientific forms of knowledge and actors. The final purpose was to demonstrate the sustainability (valued on the potential depletion or regeneration capability) of agricultural practices and adaptation strategies on a theoretical basis. Despite their polycultural landscape (maintained by low-input farming systems), escaped from the predominant landscape oversimplification, Sant’Erasmo and Vignole are also subjected to unsustainable agricultural practices, including heavy mechanisation and synthetic inputs. Coupled with natural soil salinity that is exacerbated by increasing drought periods, these practices can contribute to soil degradation and increased salinity. The reported adaptation strategies, such as zeroed, reduced, or more conscious use of machines, were guided by the need to reduce the negative impact of soil changes on productivity. Our research revealed some of them as sustainable and others as unsustainable (such as increasing irrigation to contrast soil salinity). Participatory action research is needed to support farmers in designing effective sustainable agricultural practices and adaptation strategies.

Divergence of nutrients, salt accumulation, bacterial community structure and diversity in soil after 8years of flood irrigation with surface water and groundwater.

Irrigation with saline groundwater has become necessary to overcome freshwater scarcity in the agricultural industry in arid areas. However, the effects of long-term saline groundwater irrigation on soil salinity and bacterial diversity have rarely been examined. In this study, a Lycium ruthenicum field was divided into two parts and subjected to flooding irrigation with saline groundwater (pH 7.81, total salinity 0.95g L-1) and surface water (pH 7.76, total salinity 0.36g L-1) for 8years. After 8years of irrigation, the soil salinity and salt ion content (i.e., Na+, Mg2+, K+, Ca2+, Cl- and CO32-) in the groundwater irrigation group were significantly greater than those in the surface water irrigation group (p < 0.001), with notable accumulation in the topsoil (0-5cm) (p < 0.01). The bacterial community structure differed between the surface water and groundwater irrigation groups. Salt-tolerant bacterial groups (e.g., Balneolaceae and Halomonadaceae) and species (e.g., the marine bacterium JK1007, the bacterium YC-LK-LKJ35, and Methylohalomonas lacus) dominated in the groundwater irrigation environment. Additionally, bacterial communities were associated primarily with soil salt ions (RV = 0.66, p < 0.001). The characteristic bacterial taxa in long-term groundwater irrigation soils were salt-tolerant species (e.g., the marine bacterium JK1007, the bacterium YC-LK-LKJ35, and Methylohalomonas lacus). These findings suggest that salinity is the key factor driving differences in bacterial community structure between long-term groundwater and surface water irrigation. The long-term use of surface water and groundwater for irrigation has different impacts on soil environments, with groundwater irrigation having a more pronounced negative effect. Highlights. The long-term effects of this practice on soil salt accumulation and bacterial diversity were examined. This study provides potential applications for sustainable land management in similar ecological contexts. Groundwater irrigation is characterized by saline-tolerant keystone species. Salinity filtering was used to determine the pattern of bacterial community construction.

Relationship Between Salt Accumulation and Soil Structure Fractals in Cotton Fields in an Arid Inland Basin

The relationship between soil structure and salt accumulation is unclear; thus, experiments on salt accumulation under different soil structures were conducted in cotton fields in arid areas of northwest China. Thirty-nine sets of soil samples were collected from the 0 to 180 cm profile of three experimental areas. The total salt content of the soil extracts and the particle size distribution of the soil samples were determined using a JENCO TDS and a laser particle size analyzer, respectively, and the fractal dimension of the soil structure was obtained using fractal theory. Pearson’s correlation analysis and Tukey’s test (p &lt; 0.01) were used to analyze the correlation between soil salinity, soil particle size distribution, and fractal dimensions in the three profiles. The results showed soil salinity accumulation was affected mutually by soil texture and soil structure, and soil salinity tended to accumulate in fine-grained soil. The soil fractal dimension (D) could indicate soil texture and quantify soil salinity content. When the sand content was more than 50%, there was a significant positive correlation between the soil fractal dimension and soil salinity (correlation coefficient R = 0.943). The results provide valuable insights into cotton production in arid areas.

Monitoring soil salinization and waterlogging in the northeastern Nile Delta linked to shallow saline groundwater and irrigation water quality.

Soil salinization and waterlogging are critical environmental issues affecting agricultural productivity and cultural heritage preservation, particularly in arid regions. This study investigated soil degradation processes in the archaeologically and agriculturally significant northeastern Nile Delta of Egypt. The objective was to assess the severity of soil degradation and identify key drivers related to water resources and soil characteristics to aid in the development of management strategies. The research employed a multi-faceted approach, including hydrochemical analyses (of groundwater, irrigation water, and soil), water quality indices calculations, statistical analyses, and satellite data. The results revealed high levels of soil salinization in the northern and central areas, with 64% of soil samples classified as strongly and very strongly saline. Soil chemistry indicated salinization sources linked to sodium chloride dominance. Satellite data from Sentinel-2 images and SRTM digital elevation data showed widespread severe waterlogging in the northern lowlands. The Irrigation Water Quality Index (IWQI) values indicated that 87.5% of irrigation water samples posed severe restrictions due to high salinity and sodium hazards, which were mismatched with the low soil permeability observed in 81% of the collected samples exhibiting clay texture and covering most of the study area. Furthermore, shallow groundwater at depths of 0.5-3m with high salinity was detected, where total dissolved solids exceeded 20,000mg/L, and Na-Cl water types prevailed, indicating saltwater intrusion. A strong positive correlation (r > 0.83) was found between shallow saline groundwater and soil salinity. The combination of poor irrigation water quality, shallow saline groundwater tables, and low-permeability soils created a synergistic effect that severely compromised soil health and agricultural productivity. It also posed severe risks to the structural integrity of archaeological sites and buried artifacts through accelerated physical and chemical weathering processes. This necessitates an urgent mitigation strategy to combat soil degradation in this critical area.

Extreme soil salinity reduces N and P metabolism and related microbial network complexity and community immigration rate.

Soil microbiomes are well known to suffer from the effects of rising salinity. There are, however, no current understandings regarding its specific effects on microbial metabolic functions associated with nitrogen (N) and phosphorus (P) cycling, particularly in the Yellow River Delta (YRD), one of the largest estuaries in the world. This research examined soil microbiomes at 50 sites in the YRD region to analyze their co-occurrence networks and their relationship with N (nitrification, denitrification, dissimilatory, assimilatory, fixation, and mineralization) and P (solubilization, mineralization, transportation, and regulation) metabolism processes. Our findings indicate a notable reduction in soil multifunctionality as salinity levels increase, with Halofilum-ochraceum playing a significant role in nitrification, whereas Bacteroidetes-SB0662-bin-6 helps solubilize inorganic P in highly saline areas. High soil salinity negatively affected the amoA gene involved in nitrification and increased the nosZ gene involved in denitrification in extreme salinity soil with 8.2g/kg salt content. Extreme salinity significantly reduced the expression of genes involved in inorganic P solubilization, such as ppa and ppx. Additionally, the alkaline P gene phoD exhibited significant decreases in extremely saline soils, thereby impeding the mineralization of organic P. The neutral community models indicated that microbial community immigration rate showed a linear negative relationship with soil EC in the six N and four P processes. Salinization, however, displayed a nonlinear pattern with clearly defined thresholds on the community of microbes involved in N and P cycling. Reduced microbial diversity and interactions are causing a decline in soil multifunctionality, and the soil multifunctionality and network edges jointly limited the microbial community immigration rate involved in N and P cycling. It is crucial to preserve soil microbial functions to support nutrient cycling and predict the ecological effects of soil salinization.

Spatial heterogeneity response of soil salinization inversion cotton field expansion based on deep learning

Soil salinization represents a significant challenge to the ecological environment in arid areas, and digital mapping of soil salinization as well as exploration of its spatial heterogeneity with crop growth have important implications for national food security and salinization management. However, the machine learning models currently used are deficient in mining local information on salinity and do not explore the spatial heterogeneity of salinity impacts on crops. This study developed soil salinization inversion models using CNN (Convolutional Neural Network), LSTM (Long Short-Term Memory Network), and RF (Random Forest) models based on 97 field samples and feature variables extracted from Landsat-8 imagery. By evaluating the accuracy, the best-performing model was selected to map soil salinity at a 30m resolution for the years 2013 and 2022, and to explore the relationship between soil electrical conductivity (EC) values and the expansion of cotton fields as well as their spatial correlation. The results indicate that:(1) The CNN performs best in prediction, with an R2 of 0.84 for the training set and 0.73 for the test set, capable of capturing more local salinity information. (2) The expansion of cotton fields has reduced the level of soil salinization, with the area of severely salinized and saline soils in newly added cotton fields decreasing from 177.91 km2 and 381.46 km2 to 19.49 km2 and 1.12 km2, respectively. (3) Regions with long-term cotton cultivation and newly reclaimed cotton fields exhibit high sensitivity and vulnerability to soil salinity. This study explores the excellent performance of deep learning in salinity mapping and visualizes the spatial distribution of cotton fields that are highly sensitive to soil salinity, providing a scientific theoretical basis for accurate salinity management.

Salinity Monitoring and Modelling at Different Scales: An Editorial Overview

Soil salinization is a significant abiotic process affecting arid, semi-arid, and sub-humid regions worldwide [...]

Response of Alfalfa Leaf Traits and Rhizosphere Fungal Communities to Compost Application in Saline–Sodic Soil

Soil salinization is considered a major global environmental problem due to its adverse effects on agricultural sustainability and production. Compost is an environmentally friendly and sustainable measure used for reclaiming saline–sodic soil. However, the responses of the physiological characteristics of alfalfa and the structure and function of rhizosphere fungal communities after compost application in saline–sodic soil remain elusive. Here, a pot experiment was conducted to explore the effect of different compost application rates on soil properties, plant physiological traits, and rhizosphere fungal community characteristics. The results showed that compost significantly increased soil nutrients and corresponding soil enzyme activities, enhanced leaf photosynthesis traits, and ion homeostasis compared with the control treatment. We further found that the rhizosphere fungal communities were dominated by Sodiomyces at the genus level, and the relative abundance of pathogenic fungi, such as Botryotrichum, Plectosphaerella, Pseudogymnoascus, and Fusarium, declined after compost application. Moreover, the α-diversity indexes of the fungal community under compost application rates of 15% and 25% significantly decreased in comparison to the control treatment. The soil SOC, pH, TP, and TN were the main environmental factors affecting fungal community composition. The leaf photosynthetic traits and metal ion contents showed significantly positive correlations with Sodiomyces and Aspergillus. The fungal trophic mode was dominated by Pathotroph–Saprotroph–Symbiotroph and Saprotroph. Overall, our findings provide an important basis for the future application of microbial-based strategies to improve plant tolerance to saline-alkali stress.

Exploring the growth and phytoremediation efficacy of Suaeda fruticosa in agricultural soil contaminated by shrimp aquaculture

Plants face numerous environmental challenges from biotic and abiotic stressors, with soil salinization emerging as a significant global concern. The coastal regions of Tamil Nadu, face severe environmental challenges due to discharge of saline water from shrimp farms exacerbates this issue, compromising the viability of paddy and other crops in the vicinity. This study explores the phytoremediation potential of Suaeda fruticosa in addressing soil salinity resulting from shrimp farming activities under field conditions over a 120-day period to restore soil health in salt affected soil. This research demonstrates Suaeda fruticosa’s exceptional salt tolerance and bioaccumulation potential in facilitating soil restoration. Significant enhancements were observed in various growth parameters, including 466% increase in plant height, 338% in fresh weight and 387% in dry weight. Biochemical parameters also showed substantial enhancements with total chlorophyll, protein, proline, phenol, and glycinebetaine levels increasing by 655%, 588%, 690%, 153%, and 531%, respectively. Enzymatic activities exhibited notable elevations as well, with catalase, peroxidase, and polyphenol oxidase activities escalating by 258%, 587%, and 121% respectively, indicating robust adaptation to saline environments. Moreover, Suaeda fruticosa exhibited remarkable bioaccumulation capabilities, accumulating 461 kg NaCl ha−1. This led to substantial improvements in soil characteristics, including a reduction in pH from 8.8 to 6.49, electrical conductivity from 5.7 to 1.53 dSm−1, and sodium adsorption ratio from 16.1 to 4.4 mmol L−1. The successive cultivation of Suaeda fruticosa in this study, has proven to be a viable strategy for reclaiming salt-affected lands, thereby alleviating a significant constraint on crop productivity.

Calcium Silicate Application as a Salt Stress Mitigation Strategy for Vegetables in the Salt-affected Soils of Sandy Plains of Kerala, India

Soil salinity inhibits plant growth due to osmotic stress and reduced plant and water uptake. In the Onattukara sandy plains of Kerala, saltwater intrusion is a major problem in several panchayaths near the coastal area. In uplands also, cultivation is not possible due to the salt stress from saltwater intrusion. One of the strategies for removing the inhibitory effect of salt stress on plant growth is the application of beneficial nutrients to the plants. Therefore, a study was carried out to understand the effect of calcium silicate application on mitigating salt stress in vegetables and using tomato as a test crop. A detailed germination study was conducted in laboratory conditions prior to pot culture experiment to find out the critical level of salinity for tomato and two salinity levels 30mM and 40 mM NaCl were selected for the pot culture experiment. For accessing the effect of the various levels of calcium silicate on reducing salt stress in tomato, a pot culture experiment was conducted in Onattukara region (AEU 3) in completely randomized design with ten treatments replicated thrice with varying levels of CaSiO3 from 100 kg ha-1 to 150 kg ha-1. The treatments had a significant effect on all the biometric characteristics and yield attributes of the crop. The highest fruit weight, fruit per plant, and fruit yield were observed in treatment with soil test-based NPK recommendation and 125 kg ha-1 of CaSiO3 applied. It was also observed that the relative water content was higher and the water saturation deficit was lower in this treatment. CaSiO3 application @125 kg ha-1 along with soil test-based recommendation of NPK can be recommended as a salt stress mitigation strategy for boosting vegetable production in the salt-affected soils of sandy plains of Kerala.

Ecological Aspects of Distribution and Population Status Assessment of Rhamnus erythroxyloides subsp. sintenisii (Rich.f) Mabb., a Relict Species in the Kyzylkum Desert of Uzbekistan

Rhamnus erythroxyloides subsp. sintenisii (Rech.f.) Mabb. is a relict species occurring on the remnant mountains of Kyzylkum (in Uzbekistan). Up until recently, its population status and exact distribution remained unassessed. The ecological distribution and population status of four populations of Rh. erythroxyloides subsp. sintenisii were studied. The study of its morpho-anatomical structure revealed that the studied taxon’s vegetative and generative organs demonstrate clear adaptive features to arid climate. We observed an absence of the young fraction (seedlings and juvenile plants) in the populations, which is related to irregularity of seed renewal. Furthermore, population fragmentation due to a high degree of soil salinity and the presence of organic matter has been noticed at the present stage. According to the combination of threatening factors, the current state of the population of Rh. erythroxyloides subsp. sintenisii in Uzbekistan has been estimated as disappearing (EN)—B2ab (ii, iii, iv) + C1 + E.

Monitoring soil salinity in coastal wetlands with Sentinel-2 MSI data: Combining fractional-order derivatives and stacked machine learning models

Monitoring soil salinity is essential for understanding the behavior of coastal wetland ecosystems and implementing effective management strategies. Despite the advantages of the Multi-Spectral Instrument (MSI) data for large-scale, high-frequency soil salinity monitoring, challenges remain in data preprocessing and model construction. We combined fractional-order derivative (FOD) technology with stacked machine learning models to monitor and map soil salinity using Sentinel-2 MSI data. The base models included Elastic Net Regression, Support Vector Regression, Artificial Neural Network, Extreme Gradient Boosting, and Random Forest, with Non-Negative Least Squares as the meta-learner. The results showed that low-order FOD enhanced image gradients and maintained a high peak signal-to-noise ratio, thereby improving the correlation with soil salinity. Notably, the 0.25-order FOD showed the best performance, increasing the correlation coefficient with soil salinity by up to 13 %. The stacked machine learning models effectively combined the strengths of different base models, enhancing prediction accuracy by more than 8 % compared to single models. Furthermore, combining stacked models with FOD further improved prediction accuracy, with an increase in R² of up to 9 %. The combination of 0.25-order FOD and the stacked machine learning model achieved the best performance (R² = 0.82, RMSE = 10.19 ppt, RPD = 2.38, RPIQ = 4.69). This approach provides a reference for rapid and effective large-scale digital mapping of soil salinity in coastal wetlands.