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Fluvial landscapes in the dry land parts of the world include soils with large quantities of soluble sodium carbonates and bicarbonates and abundant exchangeable sodium. The Indo-Gangetic alluvial plain (IGP) includes a large proportion of salt-affected soils in India of these 3.78 million hectares are sodic soils. Considering the problem of soil sub-surface sodicity the ICAR-Central Soil Salinity Research Institute (CSSRI), Karnal, and the Japan International Research Centre for Agricultural Sciences (JIRCAS) have con- ducted a farmers' field trial from 2019 to examine the effects of gypsum and rice residue placement by Cut-soiler machine at various lateral spacing on soil sub-surface sodicity and crop yield. The treatments include Cut-soiler assisted sub-surface application of gypsum, rice residue and gypsum + rice residue at 2.5, 5.0 and 10.0 m of lateral spacing. The result shows appreciable temporal and spatial re- duction in sub-surface sodicity and consequently increases in wheat yield during study period (2019-2021). The reduction in soil pH at 0.1 m, 0.4 m, 0.8 m and 1.2 m from Cut-soiler drain was recorded and it was observed that the reduction in soil pH was continuous and consistent from year 2019 to 2021. There was higher reduction in soil pH near to the Cut-soiler drain and this reduction was decreased with increase in distance from Cut-soiler drain. The soil pH reduced by 0.8 units (8.9 to 8.17) at 0.1 m distance in 2021. The soil pH at 0.4 m, 0.8 m and 1.2 m were 8.27, 8.46 and 8.67, respectively in same year. The wheat yield in 2.5 m lateral Cut-soiler drain was 18.3% higher than without Cut-soiler. Sub-surface sodicity management by placement of amendments along with filling material in Cut-soiler drains in turn further helped to increase grain yield of wheat and thus the amelioration effect was continuous and consistent. [ABSTRACT FROM AUTHOR]

As an essential micronutrient for many organisms, sodium plays an important role in ecological and evolutionary dynamics. Although plants mediate trophic fluxes of sodium, from substrates to higher trophic levels, relatively little comparative research has been published about plant growth and sodium accumulation in response to variation in substrate sodium. Accordingly, we carried out a systematic review of plants' responses to variation in substrate sodium concentrations.We compared biomass and tissue‐sodium accumulation among 107 cultivars or populations (67 species in 20 plant families), broadly expanding beyond the agricultural and model taxa for which several generalizations previously had been made. We hypothesized a priori response models for each population's growth and sodium accumulation as a function of increasing substrate NaCl and used Bayesian Information Criterion to choose the best model. Additionally, using a phylogenetic signal analysis, we tested for phylogenetic patterning of responses across taxa.The influence of substrate sodium on growth differed across taxa, with most populations experiencing detrimental effects at high concentrations. Irrespective of growth responses, tissue sodium concentrations for most taxa increased as sodium concentration in the substrate increased. We found no strong associations between the type of growth response and the type of sodium accumulation response across taxa. Although experiments often fail to test plants across a sufficiently broad range of substrate salinities, non‐crop species tended toward higher sodium tolerance than domesticated species. Moreover, some phylogenetic conservatism was apparent, in that evolutionary history helped predict the distribution of total‐plant growth responses across the phylogeny, but not sodium accumulation responses.Our study reveals that saltier plants in saltier soils proves to be a broadly general pattern for sodium across plant taxa. Regardless of growth responses, sodium accumulation mostly followed an increasing trend as substrate sodium levels increased. [ABSTRACT FROM AUTHOR]

This article shows the results obtained about the possibility of the indirect calculation of SDI and sodium adsorption ratio (SAR) based on electrical conductivity at 25°C (EC25) and pH data prior to and following remineralisation, using the quotient between EC25 and alkalinity (Alk). The importance of this work is to propose a new calculation method which is required to estimate with certain precision the increase in alkalinity and hardness that has been achieved with remineralisation. It is justified to investigate the relationship between the alkalinity values and the remineralised water. The novelty of this work is to have been done based on real data taken from different desalination plants as well as theoretical calculations based on the contribution of each ion to the conductivity of the water. For instance, Alk(0) ranges are from 0.5 to 2.8 mg CaCO3/L for values of EC25(0) of between 250 μS/cm and 700 uS/cm respectively. The values of pH(r) and T(r) will be those acquired “in situ” with the measuring equipment placed in line. Once all the parameters have been obtained, the Langelier saturation index LSI(r) calculation method should be SM-2330. This procedure allows LSI(r) to be estimated with an accuracy in between of +0.05 and –0.05. According to the study performed and to achieve the optimum levels indicated in Table 1, the increase in alkalinity should be at least 55 mg CaCO3/L. This implies that the increase in electrical conductivity should be within the range 85–97. The mean value of SAR or sodium absorption rate of desalinated water is around 9. This point to water that can cause damage not only to the soil but also to some crops due to an excess of sodium over calcium and magnesium. This aspect should therefore be corrected. Either with a remineralization or by adding calcium and magnesium directly with fertilizers. The sampling conditions should be optimized to prevent loss of CO2 and obtain values of pH and temperature as close to operating conditions before and after remineralization system. [ABSTRACT FROM AUTHOR]

Sodium (Na) is an essential element for all animals, but not for plants. Soil Na supplies vary geographically. Animals that primarily consume plants thus have the potential to be Na limited and plants that uptake Na may be subject to higher rates of herbivory, but their high Na content also may attract beneficial partners such as pollinators and seed dispersers.To test for the effects of Na biogeochemistry on herbivory, we conducted distributed Na press experiments (monthly Na application across the growing season) in four North American grasslands.Na addition increased soil and plant Na concentrations at all sites. Grasses in Na addition plots had significantly higher herbivore damage by leaf miners and fungal pathogens than those in control plots. Forbs with higher foliar Na concentrations had significantly more chewing insect herbivore and fungal damage.While no pattern was evident across all species, several forb species had higher Na concentrations in inflorescences compared to leaves, suggesting they may allocate Na to attract beneficial partners.The uptake of Na by plants, and animal responses, has implications for the salinification in the Anthropocene. Increased use of road salt, irrigation with saline groundwater, rising sea levels and increasing temperatures and evapotranspiration rates with climate change can all increase inputs of Na into terrestrial ecosystems.Our results suggest increasing terrestrial Na availability will benefit insect herbivores and plant fungal pathogens. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

High salinity induces osmotic stress and often leads to sodium ion‐specific toxicity, with inhibitory effects on physiological, biochemical and developmental pathways. To cope with increased Na+ in soil water, plants restrict influx, compartmentalize ions into vacuoles, export excess Na+ from the cell, and distribute ions between the aerial and root organs. In this review, we discuss our current understanding of how high‐affinity K+ transporters (HKT) contribute to salinity tolerance, focusing on HKT1‐like family members primarily involved in long‐distance transport, and in the recent research in the model plant Arabidopsis and its halophytic counterparts of the Eutrema genus. Functional characterization of the salt overly sensitive (SOS) pathway and HKT1‐type transporters in these species indicate that they utilize similar approaches to deal with salinity, regardless of their tolerance. [ABSTRACT FROM AUTHOR]

Salt stress in agricultural soils is a global issue and little information is available about the efficiency of silver nanoparticles (AgNPs) in plants under salt stress. The aim of current study was to assess the efficacy of AgNPs in improving plant growth and reducing the salt-induced damages in pearl millet. The exposure of pearl millet plants grown in pots containing soil to different doses of salinity (0, 120, 150 mM) and AgNPs (0, 10, 20 and 30 mM) significantly influenced the morphology, physiology and yield-related attributes. Salt stress remarkably increased the concentration of sodium (Na) and chloride (Cl) in different organs of pearl millet plants. This led to increase the enhancement of hydrogen peroxide (H2O2) and malondialdehyde (MDA) content and caused severe oxidative damage by augmenting the activities of antioxidant enzymes. The obvious decrease in plant growth, height, dry biomass of root and shoot, chlorophylls and carotenoid contents was observed in salt-stressed plants which ultimately reduced the yield of plants. The AgNPs remarkably improved the plant growth by reducing oxidative stress and Na and Cl uptake by salt-stressed plants. The AgNPs were also found to maintain the ionic balance of cell (Na+, K+ and Na+/K+ ratio). The AgNPs improved the superoxide dismutase, catalase activities and decreased the peroxidase activity while reduced the H2O2 and MDA contents in plants under salt stress. Overall, AgNPs increased the plant height, yield, and photosynthesis of salt-stressed plants in a dose-additive manner. [ABSTRACT FROM AUTHOR]

Salt stress caused by soil salinization, is one of the main factors that reduce soybean yield and quality. A large number of genes have been found to be involved in the regulation of salt tolerance. In this study, we characterized a soybean sodium/hydrogen exchanger gene GmNHX5 and revealed its functional mechanism involved in the salt tolerance process in soybean. GmNHX5 responded to salt stress at the transcription level in the salt stress-tolerant soybean plants, but not significantly changed in the salt-sensitive ones. GmNHX5 was located in the Golgi apparatus, and distributed in new leaves and vascular, and was induced by salt treatment. Overexpression of GmNHX5 improved the salt tolerance of hairy roots induced by soybean cotyledons, while the opposite was observed when GmNHX5 was knockout by CRISPR/Cas9. Soybean seedlings overexpressing GmNHX5 also showed an increased expression of GmSOS1 , GmSKOR , and GmHKT1 , higher K+/Na+ ratio, and higher viability when exposed to salt stress. Our findings provide an effective candidate gene for the cultivation of salt-tolerant germplasm resources and new clues for further understanding of the salt-tolerance mechanism in plants. [ABSTRACT FROM AUTHOR]

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China has a long history and has made a substantial contribution to global crop production, but lacking in potassium (K) mineral resource, have led to numerous studies of K availability in Chinese agricultural soils. In this study, we collected 2,428 surface soil samples from nine important agricultural regions to investigate available K reserves in Chinese agricultural soils. Soil highly available K (HAK) and maximally available K (MAK) were estimated using a modified sodium tetraphenyl boron (NaTPB) method. With HAK and MAK distribution maps constructed, the characteristics of available K contents distribution were visibly observed as higher in Western and Northern China, and lower in the East and South. We then used the Kriging method to estimate the HAK reserve and its potential utilization. The soil HAK reserve was predicted to maintain only crops producing >70% of the relative biomass yield for approximately 10 years in the absence of external K application. With straw returning, this utilization period was predicted to increase to about 40 years. Soil MAK content was generally less than 1,000 mg kg–1, and reached as low as <500 mg kg–1 throughout most of central and Eastern China. The results of this study graphically demonstrate the shortage of K storage in Chinese agricultural soil and its looming sustainability crisis. These findings provide a scientific basis support the improved use and protection of agricultural resources in China. [ABSTRACT FROM AUTHOR]

A pot experiment was conducted to see the effect of sodicity and iron levels on cowpea. Four levels of sodium adsorption ratio (SAR) 10, 15, 20, 25 and iron (Fe) control, 5, 10, 15 and 20 kg Fe ha-1) were tested in completely randomized design with three replications. The results indicated that application of soil sodicity having SAR 15 recorded the maximum yield, phosphorus and potassium content and uptake and nitrogen uptake of cowpea over rest of the treatments. Application of Fe 20 kg ha-1 recorded the maximum and significantly higher yield, nitrogen, phosphorus and potassium content and uptake of cowpea over rest of the treatments. Among the treatment combinations combined application of SAR 15 with Fe @ +20 FeSo4.7H2O) proved superior in all these parameters over other treatments. [ABSTRACT FROM AUTHOR]

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The objective of this study was to examine the influence of vermicompost (VC) as a soil conditioner in alleviating adverse effects of sodium in Na salt-effected soils. Therefore, the role of VC for reducing the adverse effects of Na salt on physicochemical properties of soil was investigated. Experiments were conducted with different doses of VC (0, 2.5 and 5% VC (w/w) and three different Na salt levels (0, 4 and 8 dS m−1 NaCl). Vermicompost treatments under different salinity stress levels had significant positive effects on soil physicochemical properties. Vermicompost also decreased exchangeable Na of salt-affected soils. Vermicompost treatments under different Na salt regimes enhanced soil organic matter, available phosphorus, total nitrogen, available K and cation exchange capacity of the soils. VC treatments under the low and medium Na salt levels (0 and 4 dS m−1 NaCl concentration, respectively) increased soil EC values. However, vermicompost treatments under high Na salt stress (8 dS m−1 NaCl concentration) decreased EC values, thus soil salinity. Vermicompost treatments under different Na salt regimes increased field capacity, available water capacity, saturated hydraulic conductivity, total porosity, aggregate stability and decreased bulk density of the soils. Present findings revealed that vermicompost treatments, especially 5% VC treatments were quite effecient in alleviating adverse effects of salinity and enhancing soil quality. It was concluded based on present findings that vermicompost treatments could be considered as an efficient amelioration material for reclamation of Na salt-effected soils. [ABSTRACT FROM AUTHOR]

Potassium (K+) and nitrogen (N) are essential nutrients, and their absorption and distribution within the plant must be coordinated for optimal growth and development. Potassium is involved in charge balance of inorganic and organic anions and macromolecules, control of membrane electrical potential, pH homeostasis and the regulation of cell osmotic pressure, whereas nitrogen is an essential component of amino acids, proteins, and nucleic acids. Nitrate (NO3–) is often the primary nitrogen source, but it also serves as a signaling molecule to the plant. Nitrate regulates root architecture, stimulates shoot growth, delays flowering, regulates abscisic acid-independent stomata opening, and relieves seed dormancy. Plants can sense K+/NO3– levels in soils and adjust accordingly the uptake and root-to-shoot transport to balance the distribution of these ions between organs. On the other hand, in small amounts sodium (Na+) is categorized as a "beneficial element" for plants, mainly as a "cheap" osmolyte. However, at high concentrations in the soil, Na+ can inhibit various physiological processes impairing plant growth. Hence, plants have developed specific mechanisms to transport, sense, and respond to a variety of Na+ conditions. Sodium is taken up by many K+ transporters, and a large proportion of Na+ ions accumulated in shoots appear to be loaded into the xylem by systems that show nitrate dependence. Thus, an adequate supply of mineral nutrients is paramount to reduce the noxious effects of salts and to sustain crop productivity under salt stress. In this review, we will focus on recent research unraveling the mechanisms that coordinate the K+-NO3–; Na+-NO3–, and K+-Na+ transports, and the regulators controlling their uptake and allocation. [ABSTRACT FROM AUTHOR]

In this study, effects of glycerol (10, 20, and 30 wt%) and Sodium Montmorillonite (Na-MMT) (0%, 2.5%, and 5%) contents on the degradation of corn starch polymers were investigated. Films were prepared by casting corn starch solution using a modified method to enhance the nanoclay distribution. Biodegradability studies were performed by enzymatic and burial tests using pristine and enriched soils. The biodegradability of samples in pristine soil was faster, and all samples were fully degraded in 6 months. The effect of nanoparticles on the mass reduction in degradation was more pronounced than that of glycerol. In all glycerol concentrations, Na-MMT addition increased tensile strength. FTIR tests showed that degradability was related to glycerol leaching at first and then cleaving of α-1,4 bonds of starch, indicating the action of α-amylase produced by soil microorganisms. Good agreement between soil burial tests and enzymatic degradation was observed. An optimum Glycerol/Clay ratio was observed at which d-spacing and mechanical properties were maximum. [ABSTRACT FROM AUTHOR]

Millions of acres of agricultural soils in the Northern Great Plains have excessive levels of sodium (Na) which reduces their productivity potentials. Soil function in Na-affected soils may be improved by soil amendments, but the effectiveness of these amendments is dependent on many site-specific characteristics. This study investigated how three amendments (with three application rates), gypsum, spent lime (5, 15, and 30 ton ac-1), and potassium-magnesium sulfate (1, 2.5, 5 ton ac-1), affected alfalfa (Medicago sativa L.) production and soil parameters at a site with subsurface tile drainage and a site without tile drainage over 4 yr. Notably, over the course of the study, none of the amendments affected alfalfa production or quality at either site, although the highest rate of potassiummagnesium sulfate reduced biomass production by about 10%. After 4 yr within the 0- to 6- in depth, the amendments lowered electrical conductivity (EC) and %Na at the tiled site compared to the control but not at the nontiled site. Moreover, the higher rates of each amendment decreased %Na compared to initial conditions, but after 4 yr, these treatments were not different from the control (alfalfa only). This study determined that the use of a perennial crop, such as alfalfa, may be as effective as amendments in reducing the negative effects of Na on soil properties. [ABSTRACT FROM AUTHOR]

Cation ratio of soil structural stability (CROSS) and exchangeable dispersive percentage (EDP) have been recently proposed to replace the traditional sodium absorption ratio (SAR) and exchangeable sodium percentage (ESP) for predicting soil structural stability, in conjunction with the electrolyte concentration. Both CROSS and EDP incorporate the dispersive effects as coefficients transforming K and Mg effects to equivalent Na, and flocculative coefficient transforming Mg effect to equivalent Ca. However, these coefficients are derived from the flocculating power of Na, K, Mg and Ca based on a limited number of soil clays. This study re-examines the flocculating power for a broad range of soil clays by analysing their critical flocculation concentrations (CFCs). Soil clays from 17 contrasting soils were separated and chemically treated into Na, K, Mg and Ca homoionic clays. Within the same cation treatment, there were significant differences among the measured CFC values, which can be related to their different clay mineralogy and co-existing materials in soil clays. The dispersive coefficients of K and Mg, as well as the flocculative coefficient of Mg, were seen to vary substantially in respect to the generalised values used in CROSS and EDP. The absolute errors between the specified CROSS and generalised CROSS as well as the specified EDP and generalised EDP have been calculated for the 95th percentile of possible cation concentrations. In terms of CROSS, the dispersive coefficient a [K] and flocculative coefficient b [Mg] both contribute to the absolute error, with a [K] having a greater influence than b [Mg]. In terms of EDP, the dispersive coefficient a [K] played the dominant role in causing absolute error between the specified EDP and generalised EDP, while the role of dispersive coefficient c [Mg] was not significant. The outcome of this work indicates that the soil-specific coefficients should be used to minimise the possibility of undue soil structural degradation, while the generalised coefficients are only applicable to a small range of outcomes. • CFC values of homoionic clays vary significantly among soils. • CFC of homoionic clays follows Na > K > Mg > Ca for each of the soil. • c [Mg] had negligible impact and can be dropped from EDP equation. [ABSTRACT FROM AUTHOR]

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The use of plant-bacterial association is a promising approach for the enhanced remediation of pesticides. Generally, both rhizo- and endosphere bacteria assist their host plants to survive in the contaminated environment. In this work, we have studied the individual and combined effects of wheat (Triticum aestivum) and a previously optimized bispyribac sodium (BS) degrading bacterial consortium (BDAM) on the degradation of BS and plant biomass production. Results showed that the bacterial strains of the BDAM have successfully survived in the plant rhizo-as well as endosphere and enhanced degradation of BS and plant biomass. In soil spiked with 2 mg/kg and 5 mg/kg of BS and was planted and inoculated with BDAM (P_I) showed 100% degradation of BS both in rhizosphere soil and endosphere of the plant. However, during the same period (45 days) the degradation of BS was 96 and 90%, and 93 and 84% in inoculated but un-planted (I_UP) and planted but un-inoculated (P_UI) soils spiked with 2 and 5 mg/kg, respectively. Liquid chromatography-mass spectrometry (LC-MS) analysis of the treated samples showed novel degradation products of BS. Based on the results, we concluded that plant-bacterial association is an efficient tool for enhanced remediation of BS contaminated soil and herbicide free crop production. Image 1 • Plant-bacterial partnership is an efficient approach for the remediation of BS contaminated sites. • Inoculation of BDAM has increased plant biomass and removal of BS. • Bacterial strains of BDAM survived in the rhizo- and endosphere W2. • Novel degradation products of BS were detected, and a degradation pathway has been proposed. [ABSTRACT FROM AUTHOR]

The effect of different Na concentrations on the fate of trace metals (Cd, Cu, Ni, Zn) in standard OECD soil was evaluated by performing soil leaching column experiments. Five Na concentrations added in synthetic irrigation water (0, 1, 5, 10, 50 mM) were studied in order to evaluate the fate of the metals contained in both the irrigation water leachate and the soil layer. In all experiments, metals mostly accumulated on the top soil layer (0–0.5 cm), at variable concentrations according to the Na content in the artificial irrigation water. Nevertheless, concentration peaks of metal contamination occurred at different sampling time in the soil leachates depending on the metal and on influent water sodicity. Peaks of metals in the leachate appeared simultaneously with the release of organic matter and/or release of Al, suggesting significant involvement of colloids in metals transport. Sodium concentration (10–50 mM) was demonstrated to highly reduce colloidal mobilization leading to the accumulation of more than 95% of the influent metal in the top soil layer. Conversely, low Na concentrations (1–5 mM) favored colloidal transport leading to the recovery of metals in the soil leachates. Image 1 • Effect of Na on mobilization of trace metals in soil was investigated. • Metals tend to accumulate in the top layer of soil. • Pollution is governed by sodium concentration. • TMs release into the leachate is correlated to colloids. • Interaction with colloids is highly selective. Pollution/mobility paths of trace metals through soil are governed by sodium concentration due to its effect on colloids mobilization. [ABSTRACT FROM AUTHOR]

Geochemical studies that focus on environmental applications tend to approach the chemical elements as individual entities and may therefore offer only partial and sometimes biased interpretations of their distributions and behaviour. A potential alternative approach is to consider a compositional data analysis, where every element is part of a whole. In this study, an integrated methodology, which included compositional data analysis, multifractal data transformations and interpolation, as well as enrichment factor analysis, was applied to a geochemical dataset for the Campania region, in the south of Italy, focusing in particular on the behaviour, footprints and sources of a smaller pool of elements: Al, Na, K and P. The initial dataset included 3669 topsoil samples, collected at an average sampling density of 1 site per 2.3 km 2 , and analyzed (after an aqua regia extraction) by a combination of ICP-AES and ICP-MS for 53 elements. Frequency based methods (Clr biplot, Enrichment Factor computation) and frequency spatial-method (fractal and multifractal plots) allowed identifying the relationships between the elements and their possible source patterns in Campania soils in relation to a natural occurring concentrations in geogenic material (rocks, soils and sediments) or human input. Results showed how the interpretation of concentration and behaviour of Al, Na, K and P was enhanced thanks to the application of data log-ratio transformation in univariate and multivariate analysis compared to the use of raw or log-normal data. Multivariate analyses with compositional biplot allowed the identification of four element associations and their potential association with the underling geology and/or human activities. When focusing on the smaller pool of elements (Al, P, K and Na), these relationships with the unique geology of the region, were largely confirmed by multifractal interpolated maps. However, when the local background was used for the calculation of the enrichment factor, the resulting interpolated maps allowed to identify smaller areas where the greater concentrations of P could not be possibly associated to a mineralisation (e.g., ultrapotassic rocks) but were more likely to be associated to anthropogenic input such as agriculture activities with potentially extensive use of phosphate fertilizers. The integrated approach of this study allowed a more robust qualitative and quantitative evaluation of elemental concentration, providing in particular new and vital information on the distribution and patterns of P in soils of the Campania region, but also a viable, more robust, methodological approach to regional environmental geochemistry studies. [ABSTRACT FROM AUTHOR]

In the low plain of the Bega River Basin, the anthropogenic influences manifested since the second half of the eighteenth century and imposed by the need to carry out surface drainage works of areas covered by swamp favoured the accumulation of harmful salts in the soil due to slow flow of the groundwater. The main component of groundwater composition is sodium followed by magnesium and calcium, and as anions we find bicarbonates and sulphates. A major influence over the qualitative evolution of the soil profiles is generated by the groundwater bodies. On the lower course of the Bega river were identified the groundwater bodies: GWBA 01, GWBA 02, GWBA 03, GWBA 04 located in the plain area in alluvial deposits (sands, gravels, silt, subordinate marl and clay intercalations) of quaternary age. The chemical analyses of the water samples collected from the quality monitoring boreholes, revealed exceedances of the maximum allowed concentration values, according to the regimentations of the Law on the quality of the drinking water no 458/2002 for the indicators: manganese, sodium and chlorine, therefore GWBA 01, GWBA 03, GWBA 04 are subject to qualitative risk. [ABSTRACT FROM AUTHOR]

The retardation factor (Rd) is one of the main important solute transport parameters. Its value can vary significantly depending on the method used for its determination. In this paper, the sodium Rd is experimentally determined using undisturbed sandy soil columns to compare four methods of Rd determination and assess the impact of the chosen method on the prediction of sodium movement. Column experiments in undisturbed soil samples and analytical analysis were performed. The results showed that the soil has dual-porosity and preferential pathways. The breakthrough curves were in accordance with the soil's physical characteristics. The Rd values ranged from 1.7 to 7.77 depending on the initial concentration and on the method used. These differences arise from the conceptual model of each Rd determination method. The experimental and analytical analysis indicated that the higher the Rd, the slower the movement. The methods that best reproduced the laboratory sodium movement were Ogata and Banks' (1961), Langmuir and Freundlich's isotherms. The prediction models presented smaller errors with the increase of the initial concentration. In these cases, the predicted concentrations can be overestimated up to 22.5% when using a not suitable method. These results suggest that the Rd determination method can strongly affect the prediction of the sodium movement. Because of that, it is of vital importance to evaluate each method and how they can be adequate for the soil under investigation when determining Rd. [ABSTRACT FROM AUTHOR]

Melatonin (N‐acetyl‐5‐methoxytryptamine) is an important biological hormone in many abiotic stress responses and developmental processes. In this study, the protective roles of melatonin were investigated by measuring the antioxidant defense system and photosynthetic characteristics in maize under salt stress. The results indicated that NaCl treatment led to the decrease in plant growth, chlorophyll contents and photochemical activity of photosystem II (PSII). However, the levels of reactive oxygen species increased significantly under salt stress. Meanwhile, we found that application of exogenous melatonin alleviated reactive oxygen species burst and protected the photosynthetic activity in maize seedlings under salt stress through the activation of antioxidant enzymes. In addition, 100 μM melatonin‐treated plants showed high photosynthetic efficiency and salinity. Immunoblotting analysis of PSII proteins showed that melatonin application alleviated the decline of 34 kDa PSII reaction center protein (D1) and the increase of PSII subunit S protein. Taken together, our study promotes more comprehensive understanding in the protective effects of exogenous melatonin in maize under salt stress, and it may be involved in activation of antioxidant enzymes and regulation of PSII proteins. [ABSTRACT FROM AUTHOR]

It is known that ethylene signaling is involved in the regulation of the salt stress response. However, the molecular mechanism of ethylene‐regulated salt stress tolerance remains largely unclear. In this study, an apple NAM ATAF CUC transcription factor, MdNAC047, was isolated and functionally characterized to be involved in ethylene‐modulated salt tolerance. MdNAC047 gene was significantly induced by salt treatment and its overexpression conferred increased tolerance to salt stress and facilitated the release of ethylene. Quantitative real‐time‐PCR analysis demonstrated that overexpression of MdNAC047 increased the expression of ethylene‐responsive genes. Electrophoretic mobility shift assay, yeast one‐hybrid and dual‐luciferase assays suggested that MdNAC047 directly binds to the MdERF3 (ETHYLENE RESPONSE FACTOR) promoter and activates its transcription. In addition, genetic analysis assays indicated that MdNAC047 regulates ethylene production at least partially in an MdERF3‐dependent pathway. Overall, we found a novel 'MdNAC047‐MdERF3‐ethylene‐salt tolerance' regulatory pathway, which provide new insight into the link between ethylene and salt stress. [ABSTRACT FROM AUTHOR]

Inexpensive, accurate, and rapid measurements of sodicity are required to identify the restoration options for degraded sites. This study determined the spatial variability of the percent of ammonium acetate extractable Na (%Na), apparent electrical conductivity (ECa), pH1:1, elevation and topographic wetness index, and used this information to create %Na management zones. In an 8.1 ha North Dakota field that contained Natraquolls and Calciaquolls, 1088 soil samples from the 0-0.3 and 0.3-0.6 m were collected from a 12.2 by 12.2 m geo-referenced grid. At each grid point, the elevation and ECa was determined using a differential corrected global positioning system and EM38m, respectively. Soil samples were analyzed for the %Na, EC1:1, pH1:1, and soil dispersion. Exponential semi-variogram models explained 96.7% of the ln-transformed %Na data in the 0-0.3 m soil depth, and %Na was correlated to EC1:1 (r = 0.54), pH1:1 (r = 0.68), clay dispersion (r = 0.68), ECav (r = 0.49), and ECah (r = 0.57). Forward stepwise regression models based on elevation, EC1:1, pH1:1, and ECah explained 64 and 74% of the %Na variability in the surface 0.3 m and subsurface 0.3-0.6 m, respectively. Management zones were identified that reduced the %Na variability up to 82%. [ABSTRACT FROM AUTHOR]

The gradual response of CAB-6P sour cherry (Prunus cerasus L.) plants to NaCl-induced salinity stress (60 mM NaCl) was investigated in a short-term hydroponic experiment, based on parameters relating to the growth, water relations, chlorophyll and mineral nutrition. The results showed that CAB-6P plants are very sensitive to salinity stress because their growth and leaf chlorophyll concentration were both affected negatively from the 3rd and 5th day, respectively, after incurring salinity stress. Since root growth was suppressed more severely than shoot growth, the shoot to root ratio was significantly increased under saline conditions. The concentrations of Na in leaves and stem of NaCl-treated plants were much lower than those measured in roots, suggesting Na exclusion mechanism from the shoot. The opposite trend was observed for Cl, indicating Cl inclusion mechanism to leaves. As regards the concentrations of Ca, Mg, P, K, Na, Fe, Zn and Mn, they were not changed in higher salinity conditions, apart from K, concentrations of which in leaves and roots were significantly increased and decreased, respectively (K translocation to leaves). Salinity further reduced K/Na ratio in root and stem as well as leaf water and osmotic potentials, whereas leaves of control and NaCl-treated plants presented similar turgor potential and K/Na ratio. These data add very important information to our knowledge about the physiological events occurring in sour cherry plants after even short-term exposure to salinity. [ABSTRACT FROM AUTHOR]

Crop available soil potassium is generally low and on the decline in the southeastern states of the USA because of the increasing crop and runoff removal and decreasing application of potassium fertilizer. Hypertension-related mortality rates are also high in the southeastern states and are on the rise. Among 41 elements analyzed from 4856 sites across all 48 states, potassium is identified as the only independent element whose soil concentration has significant association with spatial disparities of essential hypertension and hypertension-related mortality rates in the 48 states between 1999 and 2014. Essential hypertension and hypertension-related mortality rates of the 6 states with the lowest soil potassium concentration are about 50-26% higher than that of the 6 states with the highest soil potassium concentration in the 48 states (RR: 1.50, 1.26, low CI 95% 1.47, 1.25 and upper CI 95% 1.53, 1.27, respectively). Though sodium was not identified as an independent factor, an apparent significant inverse correlation exists between hypertension prevalence rates and soil sodium concentration in the 48 states (r = − 0.66, p = 0.00). There likely has been a decline of potassium in USA produces per unit weight over time and a likely association between this decline and increasing hypertension rate, particularly in the southeastern states. Hence, results of this study suggest the need of increasing potassium intakes for reducing hypertension-related mortality rates in the southeastern states. Results of this study also support further examination of potential benefits of sodium from mixture of non-chloride salts in natural produces. [ABSTRACT FROM AUTHOR]

Abstract: Calcium–sodium exchange equilibria were studied at 15 and 25 °C in 2 smectite dominant soils belonging to Typic Haplustalf (Bundi Series) and Typic Pellustert (Chambal series) of Chambal Command Area of Rajasthan (India). These soils had preference for Na+ over Ca2+; however, the soil of Bundi Series at low Na saturation (10%) showed a preference for Ca2+ at lower temperature only. Higher specificity for Na+ in Chambal Series was related to the presence of zeoloites. The relationship between exchangeable sodium ratio and sodium adsorption ratio was nonlinear, and Chambal Series could maintain relatively lower sodium adsorption ratio even at higher exchangeable sodium ratio. Among different calculated selectivity coefficients, Gapon selectivity coefficient (KG) registered the lowest coefficient of variation. The values of thermodynamic equilibrium constant (K) were greater than unity indicating higher preference for Na+, especially in Chambal Series. The Ca↔Na exchange reaction was associated with an increase in the entropy of the system in these soils. [ABSTRACT FROM AUTHOR]

Plant community structure studies on derelict sites are providing significant insights into vegetation dynamics to ensure the success of future revegetation projects in such areas. Therefore, the present study was conducted to evaluate the changes in soil physico-chemical and biological properties at abandoned red mud dumps (RMD) compared to residential (RS) and forest (FS) sites, coupled with their consequent impacts on the plant community structure. An attempt was also made to identify the indicator species that thrive only under unfavourable red mud conditions. Soil at RMD showed relatively high bulk density, alkalinity, salinity and exchangeable sodium percentage along with poor nutrient status and low microbial activity. Though toxic metals (Cd, Cr and Pb) were higher at RMD, their phytoavailabilities were lower compared to FS site. Number of herb-, shrub- and woody species at RMD were although low, but a significant number of species were acclimatized to the unfavourable soil conditions. Shrub species were maximally affected at RMD, followed by woody- and herbaceous species. Important value index of sensitive species was low while that of tolerant species was higher, and was accredited to altered soil properties. Presence of invasive species such as Acacia nilotica , Caesalpinia bonduc , Stylosanthes scabra and Urena lobata at only RMD may be used as an indication for high toxic metal contamination along with high alkalinity, salinity and poor nutrient contents. Principal component and canonical correspondence analyses revealed that woody and herbaceous species were mainly affected by soil alkalinity, salinity, exchangeable cations, bulk density, porosity, moisture content and phytoavailable metals. Shrub species were primarily influenced by soil organic carbon, nitrogen, available phosphorus, bulk density, porosity, moisture content, soil biological parameters, total (Fe, Mg, Cd, Cr and Pb) and phytoavailable metals. Domination of herbaceous species in the plant community indicated their tendency towards a definite selection strategy in response to altered soil properties. The identified tolerant herbaceous species may be suitable candidates for future red mud reclamation strategies. [ABSTRACT FROM AUTHOR]

Soil salinity and sodicity are important factors leading to soil degradation. Understanding the changes in soil salinity and sodicity is important to maintain soil quality and health and for sustainable land use. The main objective of this study was to investigate the short-term influences of land uses on soil salinity and sodicity in northeastern China. The eight dominant soil soluble ions (sodium, potassium, calcium, magnesium, carbonate, bicarbonate, chloride and sulfate), pH, electrical conductivity (EC), total soluble salt content and sodium adsorption ratio (SAR) were determined at 0–50 cm depth under five land uses consisting of corn ( Zea mays L.) cropland (Corn), alfalfa ( Medicago sativa L.) forage land (Alfalfa), Leymus chinensis (Trin.) Tzvelev grassland (AG), Leymus chinensis (Trin.) Tzvelev grassland for mowing (AG + M) and restored grassland (RG). The results showed that sodium was the predominant cation in Songnen grassland, while the contents of carbonate, bicarbonate, chloride and sulfate had slight differences in the 0–50 cm depth. Compared with soil salinity, soil sodicity was a more serious problem due to the higher soil pH and SAR. EC and SAR were more sensitive to land use conversions due to the higher discrimination ability and value ranges by different land use treatments. Under AG + M, AG and RG treatment, soil EC (20.59%, 23.03% and 19.61%, respectively) and SAR (42.46%, 39.66% and 37.62%, respectively) were lower in the 0–10 cm depth, while soil EC (36.03%, 25.75% and 17.40%, respectively) and SAR (30.86%, 20.18% and 23.09%, respectively) in the 10–50 cm depth were higher than those under Corn. Soil EC and SAR under Alfalfa in the 0–50 cm depth were 4.69% and 1.97% lower than that under Corn, demonstrating that alfalfa planting was better than other land uses to improve soil salinity and sodicity in northeastern China. These results suggested that soil sodicity was a very serious problem in the Songnen grassland, and soil salinity and sodicity can be expected to gradually decrease with the conversion of cropland to grasslands in semi-arid agroecosystems. [ABSTRACT FROM AUTHOR]

Three olive (Olea europaeaL.) cultivars Nabali Baladi (NB), Nabali Muhassan (NM), and Grossi Di'Espagna (GE) were evaluated under salt stress. Seedlings were treated with salinity induced by a 3:1 ratio of calcium chloride and sodium chloride to four concentration levels measured as electrical conductivity (EC) [1.2, 4.1, 7.0, and 14.0 dS/m] for 122 days. Olive seedlings varied in their response to salinity. In all treatments, NB had the highest root; stem and leaf dry weights had among the highest total plant dry weights, specific stem length (SSL) and relative water content (RWC). NB seedlings maintained the highest stomatal conductance at 7.0 dS/m and highest chlorophyll index at 14.0 dS/m. Olive seedlings that tolerated salt tolerance developed mechanisms of nutrient acquisition and distribution in the organs, by storing minimal amounts of sodium (Na+) and chloride (Cl−) in the stems and loading the most in the leaves and roots. [ABSTRACT FROM PUBLISHER]

The reclamation of saline sodic soils requires sodium removal and the phytoremediation is one of the proven low-cost, low-risk technologies for reclaiming such soils. However, the role of Phragmites australis in reclaiming saline sodic soils has not been evaluated extensively. The comparative reclaiming role of P. australis and gypsum was evaluated in a column experiment on a sandy clay saline sodic soil with ECe 74.7 dS m−1, sodium adsorption ratio (SAR) 63.2, Na+ 361 g kg−1, and pH 8.46. The gypsum at 100% soil requirement, planting common reed (P. australis) alone, P. australis + gypsum at 50% soil gypsum requirements, and leaching (control without plant and gypsum) were four treatments applied. After 11 weeks of incubation, the results showed that all treatments including the control significantly reduced pH, EC, exchangeable Na+, and SAR from the initial values, the control being with least results. The gypsum and P. australis + gypsum were highly effective in salinity (ECe) reduction, while sodicity (SAR) and Na+ reductions were significantly higher in P. australis + gypsum treatment. The reclamation efficiency in terms of Na+ (83.4%) and SAR (86.8%) reduction was the highest in P. australis + gypsum. It is concluded that phytoremediation is an effective tool to reclaim saline sodic soil. [ABSTRACT FROM AUTHOR]

Background: Selecting for low concentration of Na+ in the shoot provides one approach for tackling salinity stress that adversely affects crop production. Novel alleles for Na+ exclusion can be identified and then introduced into elite crop cultivars. Results: We have identified loci associated with lower Na+ concentration in leaves of durum wheat landraces originating from Afghanistan. Seedlings of two F2 populations derived from crossings between Australian durum wheat (Jandaroi) and two Afghani landraces (AUS-14740 and AUS-14752) were grown hydroponically and evaluated for Na+ and K+ concentration in the third leaf. High heritability was found for both third leaf Na+ concentration and the K+/Na+ ratio in both populations. Further work focussed on line AUS-14740. Bulk segregant analysis using 9 K SNP markers identified two loci significantly associated with third leaf Na+ concentration. Marker regression analysis showed a strong association between all traits studied and a favourable allele originating from AUS-14740 located on the long arm of chromosome 4B. Conclusions: The candidate gene in the relevant region of chromosome 4B is likely to be the high affinity K+ transporter B1 (HKT1;5-B1). A second locus associated with third leaf Na+ concentration was located on chromosome 3BL, with the favourable allele originating from Jandaroi; however, no candidate gene can be identified. [ABSTRACT FROM AUTHOR]

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Mineral transformation and soot formation are the two governing mechanisms for fine particle formation in the early stage of coal combustion. The interaction between the evaporative alkali species and soot, which can have significant effect on fine particle formation, however, is not fully understood. To investigate the interaction between Na and soot in the early stage of coal combustion, we characterized the particles derived from four coals samples, including acid-washed and Na-loaded samples, under both the pyrolytic and oxidizing atmospheres. It was found that Na can reduce the soot yield and particle size under the pyrolysis condition. The Na-doped soot was formed by flame synthesis of vaporized minerals and soot precursors, and the Na content had a strong effect on soot oxidation activity. The Na-soot interaction was found to reduce the fine particle yield in the early combustion stage, as the high Na concentration and strong sooting tendency of a sodium doped bituminous (YK-Na) resulted in a lower fine particle yield. A schematic of the Na-soot interaction pathways is proposed based on the experimental results. Catalyzing soot oxidation and eliminating ultrafine mineral particles were found to be the two principal ways by which Na-soot interaction affects the formation and evolution of fine particles. [ABSTRACT FROM AUTHOR]

Sewage sludge and green manure have become widely used organic amendments to croplands in many regions of the world. However, the amending effect of the combination of sewage sludge with green manuring in reclaimed coastal mudflat salt-soil has been unclear yet. This paper was one of earlier studies to investigate and evaluate the effects of sewage sludge amendment combined with green manuring on selected soil physicochemical properties of the mudflat soil in a rain-fed agroecosystem. The mudflat salt-soil was amended by one-time input of sewage sludge at the rates of 0, 30, 75, 150, and 300 t ha−1. After green manuring for three consecutive seasons, maize (Zea mays L.) was planted in 2013 and 2014. The results showed that SSA combined with green manuring decreased bulk density, pH, salinity, and exchangeable sodium percentage of the topsoil (0–20 cm soil layer) and increased aggregate stability, cation exchange capacity, and N and P concentration of the topsoil. As a result, the maize yield increased with the increase of SSA rates. Sewage sludge combined with green manuring can be applied in coastal mudflat salt-soil amendment, which provides an innovative way to create arable land resources and safe disposal of sewage sludge. [ABSTRACT FROM AUTHOR]

Selective separation of sodium with citric acid leaching from red mud has been put forward. The main factors and dealkalization mechanism by using inductively coupled plasma atomic emission spectroscopy, X-ray diffraction, and shrinking core model were studied. The results show that the dealkalization rate reached more than 95% under the following conditions: citric acid dosage of 15%, liquid-to-solid ratio of 7 mL/g, leaching temperature of 100°C, stirring speed of 300 rpm, and leaching time of 120 min. Sodium easily dissolved in the solution by citric acid leaching. The dealkalization process was controlled by internal diffusion and the apparent activation energy (Ea) was 19.43 kJ/mol. [ABSTRACT FROM PUBLISHER]

This survey examined the element toxicities in wheat grown in naturally waterlogged farmer's sodic fields. Seven sites located in three districts (Faizabad, Pratapgarh, and Ambedkar Nagar) of eastern Uttar Pradesh, India were selected for the study. The data on soil redox potential (Eh), soil pH, soil electrical conductivity (EC), waterlogging duration, and crop age during waterlogging were recorded at the time of plant sampling in all the sites. Waterlogging caused a reduction of 21% to 65% in shoot dry weight in the survey sites. During waterlogging, the concentrations of iron (Fe), aluminum (Al), and sodium (Na) in leaves increased dramatically; the values of these elements were many folds higher than their reported critical toxicity levels (Fe-100 ppm, Al-50 ppm, and Na-8000 ppm, respectively). The results support the hypothesis that element toxicities occur during waterlogging in wheat grown in farmer's sodic field and identified Fe, Al, and Na toxicities as a major constraint for wheat production in the study area. [ABSTRACT FROM PUBLISHER]

Purpose: Takyric solonetz is spread widely across the arid area of northwest China. The extremely poor soil structure and low hydraulic conductivity (K < 0.1 mm day) hinder its amelioration. The purpose of this study was to investigate the soil salt leaching characteristics, nutrient contents, and distributions in the impermeable saline-sodic soil reclaimed with an improved drip irrigation method, and to explore the impacting mechanisms of agronomic practices involved on the amelioration. Materials and methods: A 3-year field experiment was conducted to investigate the success of planting Lycium barbarum L. in the highly saline-sodic wasteland of takyric solonetz using drip irrigation. The soil beneath the drip emitters near the plants was replaced with sand in niches that were 0.2 m in ground diameter and 0.2 m deep. Five treatments based on soil matric potential (SMP) were designed to find the optimal irrigation schedule: −5 kPa (S1), −10 kPa (S2), −15 kPa (S3), −20 kPa (S4), and −25 kPa (S5). Results and discussion: A significant improvement was found in soil infiltration capability, which was demonstrated by the increasingly enlarged wetted area beneath the drip emitter. This improvement was resulting from the combined affects of all the agronomic practices involved, including drip irrigation, sand-filled niches, film mulching. After 3 years, soil salt leaching rates in S1-S5 root zones were 68.16 , 39.45 , 26.56 , 25.14 and 10.40%, respectively, indicating that the higher SMP improved soil salt leaching. The increased soil EC/SAR ratio reflected the amelioration of soil physical properties. After planting, the soil nutrient status considerably improved. N fertilizer, which often was leached away, should be applied in the latter half of an irrigation event. Available P content in the soil was relatively low and it was necessary to apply adequate P fertilizer to meet crop growth needs, while the studied soil was rich in K and moderate supplement of K fertilizer was proposed. After 3 years, S2, S3, and S4 produced the significantly higher dry fruit yields (∼900 kg ha), which were close to those produced by local farmland. Conclusions: Our findings indicated that an improved drip irrigation made the reclamation of an impermeable saline-sodic soil possible. The key operations included drip irrigation, sand-filled niches beneath drip emitters, ridge tillage, film mulching, and the use of thresholds to control SMP. [ABSTRACT FROM AUTHOR]

Irrigating crops with reclaimed water from sewage treatment plants can contribute to the conservation and augmentation of the water resources in arid regions. Many countries in the Middle East, North Africa and Sub-Saharan Africa are suffering from serious water shortages. Three field studies were conducted during the period 2010-2011 to assess yield components and chemical constituents of wheat, cowpea and maize crops grown in rotation with reclaimed water for irrigation in comparison with desalinated and groundwater. The reclaimed water irrigation increased wheat plant height (cm), chlorophyll, leaf area (cm), leaf length (cm), grain yield (t ha) and the water productivity (kg grain m). It improved all cowpea growth parameters under study except the dry forage yield. Nitrogen was also higher under reclaimed water irrigation in wheat tissue, cowpea pods and maize cobs. Reclaimed water had no effect on the element concentrations in wheat, cowpea and maize except for nickel concentration in wheat plants, and Sodium and Manganese concentrations in maize plants. Using reclaimed water for irrigation increased the yield parameters of wheat, cowpea and maize. However, all the studied element concentrations in wheat, cowpea and maize were within the normal limits after irrigation by reclaimed water. It can be concluded that reclaimed water usage will have significant positive impacts on yield and water productivity. [ABSTRACT FROM AUTHOR]

This greenhouse study evaluated nitrogen and sodium relations of three desert graminoids (Distichlis spicata, Leymus triticoides,andJuncus arcticus) as affected by availability of surface water, subsurface water or both. These species are amply distributed in desert wetlands of western USA where surface and subsurface water are differentially available. Plants of the three species were collected from two areas of ecological distribution: Bishop, California and Burns, Oregon. Because nitrogen and sodium uptake by plants is highly linked to water availability we established three general hypotheses for this study: (1) nitrogen uptake would be greater when plants have surface water available, (2) sodium uptake would be greater when plants do not have surface water available, and (3) there are populations’ differences in the response of the species to water availability. We grew plants in two-layer pots in which soil water content in the upper and lower layers was controlled independently. The first hypothesis was partially supported as onlyLeymus triticoidesseemed to preferentially depend on the top layer for nitrogen acquisition. With respect to the second hypothesis sodium concentration was indeed greatest when plants had no surface water, but only inD. spicata. The third hypothesis was also partially supported. The Oregon population ofJ. arcticushad 15% more nitrogen than the California population and the California population ofD. spicatahad 18% more sodium than the Oregon population. Our results underline the plant nutrient uptake implications of differential availability of water pools for common desert graminoid species. [ABSTRACT FROM AUTHOR]

Seedlings ofS. robustuswere exposed to increasing NaCl concentrations (0, 50, 100, 150, 200, 250, and 300 mM) for 50, 100, and 150 days, in greenhouse conditions. Total dry weight and salt tolerance index decreased gradually with increasing NaCl concentrations. The optimum growth ofS. robustus(4.12 to 5.25 g · plant−1) was obtained between 0 and 150 mM at 150 days after salt stress. Foliar chlorophyll a and total chlorophyll contents increased with NaCl concentration at 50 days after treatment. There was no significant effect of salinity on chlorophyll a, b and total chlorophyll contents at 100 and 150 days after treatment. Higher Na contents were found in the shoots as compared to the roots. The Na content increased, while K decreased with increasing NaCl concentrations, suggesting competitive inhibition between absorptions of Na and K as a consequence, the K/Na ratios in shoots and roots decreased with increasing salinity. The proline contents inS. robustuswere more pronounced at 300 mM (2.02 µmol/g), 250 mM (2.64 µmol/g), and 200 mM NaCl concentrations (2.98 µmol/g) for 50, 100, and 150 days, respectively, as compared to the treatment without added NaCl. Overall,S. robustuscould be considered as salt tolerant on the basis of their performance in biomass production, accumulation of Na, similar foliar chlorophyll a, chlorophyll b and total chlorophyll contents, and accumulation of proline with increasing salinity. The potential ability ofS. robustusto accumulate significant amounts of Na makes this halophyte promising as a desalinization tool of salted soils. [ABSTRACT FROM AUTHOR]

This investigation was carried out for evaluation of indole-3-acetic acid production by bacteria under salinity and salinity-sodicity stress. A total of 298 bacteria were isolated from soils with different levels of electrical conductivity and sodium adsorption ratio. Then, ability of indole-3-acetic acid production under salinity, salinity-sodicity and l-tryptophan concentrations was analyzed. The results indicated that the ability of growth and indole-3-acetic acid production among bacteria was significantly affected by salinity, salinity-sodicity and l-tryptophan concentration. The one of the bacterial species, Arthrobacter siccitolerans, that were isolated from saline-sodic soils can adjust its indole-3-acetic acid production to different levels of salinity and salinity-sodicity stress conditions. Also, its l-TRP use efficiency under salinity-sodicity stress was 5.01% and reported as the most efficient bacterium. Seed inoculation of A. siccitolerans enhanced wheat aerial and root dry matter under salinity-sodicity stress with respect to control by 10.03 and 15.17%, respectively. The study indicates the different effects of salinity-sodicity on indole-3-acetic acid indole-3-acetic acid production and the potential of A. siccitolerans for production of indole-3-acetic acid and enhancing growth of wheat under salinity and salinity-sodicity stress. [ABSTRACT FROM AUTHOR]

Over the past 60 years, road deicers (i.e. road salt) have been applied to roadways in high latitudes to improve road conditions in winter weather. However, the dissolution of road deicers in highway runoff creates waters with high concentrations of sodium, which can mobilize soil metals via soil cation-exchange reactions. While several studies have detailed the interactions of road salt-rich solutions and surface and ground waters, less attention has been given to how local hydrologic flowpaths can impact the delivery of these solutions to near-road soils. Between 2013 and 2014, soil water samples were collected from a roadside transect of lysimeter nests in Pittsburgh, Pennsylvania (USA). Soil water samples were analysed for metal concentrations and resulting data used to examine cation dynamics. While patterns in soil water calcium and magnesium concentrations follow patterns in soil water sodium concentrations, additional processes influence patterns in soil water potassium concentrations. Specifically, we observe the highest calcium and magnesium concentrations in the deepest lysimeters, suggesting divalent cations are mobilized to, and potentially accumulate in, deeper soil horizons. In contrast, soil water potassium concentrations do not follow this pattern. Additionally, in all examined elements (Ca, Mg, K, Na, and Cl), the timing of concentration peaks appears be influenced by a combination of both distance from the roadside and sampling depth. These relationships not only suggest that multiple soil water flowpaths interact with our study transect but also confirm that road salt plumes persist and migrate following the road salting season. Characterizing the interactions of sodium-rich solutions and roadside soil cation pools clarifies our understanding of metal dynamics in the roadside environment. A deeper understanding of these processes is necessary to effectively restore and manage watersheds as high total dissolved solid solutions (e.g. road deicing melt, unconventional natural gas brines, and marginal irrigation water) continue to influence hydrological systems. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Supplementary irrigation is widespread in the Humid Pampa of Argentine, where the main source of water for irrigation has elevated content of sodium bicarbonate. The combination of irrigation and rain increases the sodium absorption ratio of soil (SARs), consequently raising the clay dispersion and reducing infiltration. The water quality standards for irrigation indicate that SARs values ​​should remain below 3.5. An alternative to mitigate these disadvantages is the application of a gypsum amendment. This study targeted the following objectives: measure the impact of tillage and the addition of gypsum on: infiltration, bulk density, sodium content and crop yield in a soil (Argiudoll and petrocalcic Paleudoll association) under no-till with supplementary irrigation. One treatment consisted of applying a gypsum liming of particle size less than 3 mm. After application, the plots were tilled to a depth of 15 cm. Sunflower ( Helianthus annuus L .) was seeded 30 days after the completion of the amendment. Applying gypsum improved water infiltration into the soil. Tillage treatment without adding gypsum reduced SARs and increased infiltration the same way as tillage and gypsum treatment. This can be attributed the dissolution of native or precipitated carbonate by irrigation water. Tilled treatments, with or without amendment, had higher yield compared to no-till treatment. [ABSTRACT FROM AUTHOR]

Dispersive soil has poor physical properties, which reduce porosity, air and water movement. These properties can reduce crop production and create problems with soil stability under buildings and infrastructure. Traditionally, clay dispersion has been related to the exchangeable sodium percentage ( ESP) of soil or to the sodium adsorption ratio ( SAR) of soil solutions. However, the roles of the other exchangeable cations, potassium and magnesium, in clay dispersion have been debated in the literature and their importance is unresolved. Based on the relative dispersive and flocculating powers of sodium, potassium, magnesium and calcium, a new concept for describing dispersive soil is proposed. This defines the net dispersive charge as the difference between the dispersive charge, calculated from the concentration of exchangeable cations measured at a given soil pH and their dispersive powers, and the flocculating charge, calculated from the concentrations of cations in dispersed solutions and their flocculating powers. The net dispersive charge of a soil determines the clay dispersion. Clay disperses when the net dispersive charge is positive and does not disperse when it is zero or negative. This new concept resolves controversies in the literature caused by the roles of organic matter, clay mineralogy, exchangeable cation composition and electrolyte concentration in relation to clay dispersion. Experimental confirmation of this concept is provided by the analytical data of 96 soil samples collected from different parts of South Australia and Victoria in Australia and from previously published data. Possible methods of estimating net dispersive charge from soil solutions are discussed. Highlights Examined the role of different exchangeable cations in inducing clay dispersion., The long-debated issue of the importance of different cations in dispersive soil is resolved., The net dispersive charge in soil is related to the amount of dispersed clay., Reclamation of dispersive soil requires the net dispersive charge to be zero. [ABSTRACT FROM AUTHOR]

Fifty-six sites throughout the Wimmera region of Victoria were sampled to 1 m depth, and 1:5 extracts analysed for pH, conductivity and cation content. The relationship between conductivity measured in saturated extracts and 1:5 extracts at five sites was used to calculate cation concentrations expected if saturated extracts had been prepared. Soils were generally alkaline and cations at depth were dominated by sodium. The ratio of sodium to calcium varied from <2.6 (10% of samples) to >85.5 (10%) to a maximum of 247.1. It exceeded 12.8 in 40% of samples, and exceeded 45.6 in 20% of samples, levels which are likely to reduce root growth and ability of roots to exclude sodium. Higher ratios were associated with depth, pH and conductivity. The ratio of magnesium to calcium exceeded 1 in 80% of samples, 2 in 55% of samples, 3 in 30% of samples and the maximum measured was a ratio of 7.6, suggesting plant growth may be reduced. The issues of extrapolating from experiments in solution culture to soil, and errors likely in using 1:5 extracts are discussed. [ABSTRACT FROM AUTHOR]

Soil water movement is closely related to soil tillage. However, the development of a solid understanding of the physical mechanism by which soil ionic composition influences soil water movement remains a challenge for the scientific community. In this study, the specific ion effects of Li + , Na + and K + on soil water movement in a permanently charged soil were examined, and the vertical infiltration experiment was employed. The results provided evidence of strong specific ion effects, for which cationic polarization appears to be responsible. The velocity of the wetting front in the presence of K + was up to 18.0 and 1.52 times faster than that in the presence of Li + and Na + , respectively; the water diffusion coefficient values in the presence of K + were up to 2300 and 9.451 times higher than those in the presence of Li + and Na + , respectively. At electrolyte concentrations ≤0.01 mol L −1 , water could not infiltrate into the soil in the presence of Li + . Knowledge of the interaction forces of soil particles combined with the experimental results on soil water movement indicates that the specific ion effects can be explained by cationic polarization. We concluded that the different polarizabilities among the three cations resulted in different soil electric field strengths for a given soil under a given electrolyte concentration, which led to differences in soil pore and aggregate stability, and thus differences in the soil water movement. Our results imply that it may be possible to regulate soil water movement by adjusting ionic polarization in a soil. [ABSTRACT FROM AUTHOR]

Soil saturated paste extract (SPE) electrical conductivity (ECe) and sodium adsorption ratio (SARe) are widely used measures of soluble salts used to evaluate the salinity hazard to crop growth and the sodicity hazard to soil permeability. In gypsum-bearing soils, sparingly soluble gypsum dissolves during preparation of the SPE as a result of soil water dilution. This produces a higher measured ECe and lower SARe than would be measured if only fieldsoluble gypsum were present. As part of a soil remediation project, samples were collected from the location of a former oil and gas production facility with highly saline-sodic, brine-affected soils. The naturally calcareous silt loam soil with a smectitic clay fraction was previously amended with gypsum to mitigate elevated sodicity, of concern for sodic effects on soil permeability. The equilibrium geochemical modeling software program ExtractChem was used to model ECe and SARe in the absence of excess gypsum dissolution by first modeling EC and SAR at field water content and then modeling ECe and SARe at saturated paste water content while excluding gypsum from the modeled reaction. For samples with measured ECe <3 dS m-1, ECe modeled in the absence of excess gypsum dissolution was up to 52% lower than measured, and for samples with measured SARe <2, modeled SARe was up to 53% higher than measured. As remediation progressed and ECe and SARe decreased toward target values, the magnitude of the excess gypsum effect was sufficient to affect the evaluation of remedial progress. Equilibrium geochemical modeling adjustment of ECe and SARe for gypsum dissolution that occurs as a result of SPE preparation is recommended to improve the evaluation of the progress of remediation of gypsum-bearing, salt-affected soil. [ABSTRACT FROM AUTHOR]