Exchangeable Sodium Percentage Values Research Articles

The potential of NAA and ICP-MS for determining soil dispersibility in relation to landslide incidents

Dispersive soils pose significant challenges due to their inherent tendency to rapidly respond to the presence of water, resulting in erosion and heightened susceptibility to landslides. The inclusion of sodium (Na) onto the surface of soil clay particles results in the attenuation of the electrochemical interactions between the dispersed soil, leading to the repulsion and subsequent migration of the clay particles away from one another. This study employed Neutron Activation Analysis (NAA) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to assess the Sodium Adsorption Ratio (SAR) and Exchangeable Sodium Percentage (ESP) as indicators of soil dispersibility. The results indicate that soils containing montmorillonite clay mineral exhibit greater values of SAR > 11 and ESP > 20 in comparison to soils containing other clay minerals i.e. kaolinite, illite, and vermiculite. The calculated SAR and ESP values obtained from both analyses demonstrate a notable agreement, indicating a positive correlation. In conclusion, it is apparent that both NAA and ICP-MS method has the capability to be applied for the purpose of predicting soil dispersibility in landslide-prone regions of Malaysia.

MAPPING THE SALINITY STATUS OF AGRICULTURAL SOILS BETWEEN KIRIKHAN-KUMLU IN THE EASTERN MEDITERRANEAN REGION OF TURKEY WITH GEOGRAPHIC INFORMATION SYSTEMS (GIS)

In this study, it was aimed to determine the salinity status of agricultural soils between Kırıkhan-Kumlu in the Eastern Mediterranean region of Turkey by mapping with Geographic Information Systems (GIS). For this purpose, a total of 60 soil samples were taken from 0–20 and 20–40 cm depths and from 30 different points to represent the agricultural soils of Kırıkhan-Kumlu region in the Eastern Mediterranean region of Turkey. In the soil samples, pH, cation exchange capacity (CEC) and exchangeable cation (ECC) values were determined to determine some soil properties. Total salt, salinity class, sodium adsorption rate (SAR), exchangeable sodium percentage (ESP) and soluble cations (Na, Ca and Mg) were determined to determine the salinity status of the soils. According to the results of the research; as a result of the analysis carried out to determine the salinity status of the soils; pH values were determined between 6.91–7.98; total salt content between 0.02–0.13%; SAR values between 0.023–0.044 me/100 gr; ESP values between 0.35–2.96%; soluble Na content between 0.019–0.034 me/100 gr; soluble Ca content between 0.018–0.245 me/100 gr and soluble Mg content between 0.037–0.113 me/100 gr. In addition, by applying the ESP-SAR regression relationship of the soils, it was revealed that the soils tended to alkalize towards the lower layers. The salinity values obtained as a result of the study were transferred to the Geographic Information Systems (GIS) environment and interpolated by Kriging method and a salinity map of the study area was created. In conclusion, as a result of the research conducted in the soils of the study area in the Eastern Mediterranean region, it was determined that all of the agricultural soils of Kırıkhan-Kumlu region were classified as non-saline and that the soils did not have any problems in terms of salinity.

Spatiotemporal variation in soil salinity under irrigated fields at Bochessa catchment in Central Ethiopia

AbstractSoil salinity and sodicity problems are one of the major challenges to the permanence of irrigated agriculture in Ethiopia. This manuscript, therefore, concerns its spatial and temporal variation under irrigated fields and suggests possible management options. For this investigation, eight monitoring locations were selected based on the irrigation intensity that farmers practised in the area. With each location, three irrigated farmers' fields were randomly selected for sampling purposes. Likewise, six farmers' fields from the rain‐fed system were also selected for comparison purposes. Sampling was performed at the beginning and end of each cropping season for three consecutive years from 2017 to 2019. The major physical and chemical properties of the soil were analysed in accordance with standard laboratory procedures. A linear model of two‐way analysis of variance was used to analyse parameters across time and space. The results indicated that the majority of the soil properties studied showed significant differences (p < 0.05) over time. This implies that the change is in accordance with the seasonal soil property, possibly due to irrigation practices. Similarly, approximately 90% of the soil properties studied showed noticeable differences (p < 0.05) across locations. Almost all salinity indicators showed an increasing trend in irrigated fields compared to their situation in rain‐fed fields. For instance, the electrical conductivity (EC) and exchangeable sodium percentage (ESP) values across the fields ranged from 0.54 to 0.82 dS m−¹ and 8–1%, respectively, with maximum values observed in irrigated fields. This implies that irrigation practices influence soil properties in the area. In addition, the ESP values approaching the maximum permissible limit suggest that sodicity may cause more problems than salinity in the area. Therefore, agronomic practices (e.g. residue management, deep tillage, salt‐tolerant crops and periodic fallowing), irrigation and drainage management practices, and amendments may help farmers mitigate salinity and sodicity problems in the area.

Assessment of salt‐affected soil in Indo‐Gangetic Plain of Uttar Pradesh and prediction using regression model

AbstractIn the present study, multiple sites in the Indo‐Gangetic Plain (IGP) were examined, and most of the sites were found to be non‐saline, with electrical conductivity (EC) values below 4.0 dSm−1. The highest value of EC 8.5 dSm−1 was reported for samples collected from JAN‐2, which, followed by site RBL‐3, also shows a high value of EC 6.5 dSm−1. The highest CEC (cmolkg−1) was reported in samples collected from site JAN‐1 (8.4), JAN‐2 (8.2), and JAN‐3 (8.21), and the lowest at RBL‐2 (3.99). The highest exchangeable sodium percentage (ESP) value of 34.07% was observed at RBL‐3, indicating a potential salinity risk associated with elevated sodium contents. The analysis showed that salt was present at all study sites, and there were strong correlations between the variables examined. The relationship between measured ESP and predicted ESP shows a strong correlation with an r2 value of 0.91, indicating the applicability of ESP–sodium adsorption ratio (SAR). Paired samples t‐test results p‐value = 0.27 indicated no significant difference (p > 0.05) between the soil ESP values predicted by the soil ESP–SAR model and those obtained through laboratory testing. The statistical results of the study suggested that the soil ESP–SAR model was reliable for predicting ESP values. The soil ESP differences between the two methods were normally distributed, and the 95% limits of agreement were calculated as −7.79 and 5.55. The mean difference between the ESP–SAR model and the “Measured” method was calculated as 2.24, representing the average deviation between the two. The study presents the ESP–SAR model as a cost‐effective and efficient method for estimating soil ESP and assessing soil salinity. By analyzing soil properties and validating the model, it provides valuable insights for policymakers and stakeholders in combating agricultural land degradation in the IGP. The novelty lies in its comprehensive evaluation of soil salinity indices, reinforcing the applicability of the ESP–SAR model for future research and agricultural management.

Effects of the amendment with almond shell, bio-waste and almond shell-based biochar on the quality of saline-alkali soils.

This study aimed to evaluate the effect of the amendment with almond shell bio-waste (AS) and almond shell-based biochar (ASB), in different mass ratios (5, 10, and 15%), on the physicochemical properties of three different saline soils, using the growth of arugula seedlings as a bioindicator of the enhancement achieved. Data were analyzed based on a completely randomized design in a factorial arrangement with four replications. The results showed that the low-salinity soil (T1) presented the best physicochemical characteristics and growth parameters. The addition of AS and ASB in low proportions to the saline soils reduced the pH and electrical conductivity values. An increase in the amendment proportion led to an increase in these variables. Moisture, organic matter, and organic carbon increased, and the cation exchange capacity decreased, generating positive effects on soil quality. The values of exchangeable sodium percentage (ESP) showed that T3 presented the highest sodicity, followed by T2 and T1. The treatment with 5% ASB produced better results regarding total plant length, fresh and dry weights, leaf area, and leaf chlorophyll content. Finally, linear regression models were applied to describe the dependence of the agronomic variables on the ratio of biochar added.

Reclamation of Saline Soil under Association between Atriplex nummularia L. and Glycophytes Plants

Phytoremediation is an efficient technique for the reclamation of salt-affected soils by growing plants. The present study aims to evaluate the intercropping of halophyte Atriplex nummularia Lindl. with naturally occurring species (Mimosa caesalpiniifolia Benth, Leucaena leucocephala (Lam.) de Wit and Azadirachta indica A. Juss.) adapted to semiarid regions as a management capable of enhancing the phytoremediation capacity of these species. A field experiment was conducted in a randomized block and contained four replicates. Species were cultivated alone and in association with A. nummularia to evaluate their potential uses in the reclamation of soils. Exchangeable Ca2+, Mg2+, Na+, and K+, as well as salinity and sodicity variables, were evaluated. The evaluations were performed at 9 and 18 months of plant growth. The results indicated that A. nummularia individualized was the treatment most efficient; with reductions of 80%, 63%, and 84% in electrical conductivity, sodium adsorption ratio, and exchangeable sodium percentage values, respectively at 18 months compared to starting of the experiment. However, the use of A. nummularia and species adapted to the semiarid in association, or even alone, promoted beneficial effects on the soil quality after the establishment of the plants.

Combined Application of Organic Amendments and Gypsum to Reclaim Saline–Alkali Soil

Saline–alkali soils have high sodicity, high pH, and high levels of soluble salts, as well as carbonates. This study aimed to evaluate the effect of cattle manure and chicken manure combined with gypsum at three levels on reclaiming a saline–alkali soil, through a soil column experiment. Combined treatments were more effective than those of sole gypsum in reducing the initial exchangeable sodium percentage (ESP) below 5%. Electrical conductivity (ECe) was lowered below 1.6 dS m−1 by all treatments, except the control. The higher effectiveness of manures combined with gypsum can be explained by their synergistic effect on Na+ displacement and subsequent soil structure improvement, leading to an enhancement in the leaching process, and then the salinity/sodicity reduction. Soluble salts and Na+ were considerably reduced in all treatments at the first leaching. Soil ESP and ECe threshold values from the US Salinity Lab classification were reached by any treatment, except the control. The addition of cattle manure or chicken manure might enhance the reclamation effect of gypsum with leaching for some saline–alkali soils.

Afforestation affects vertical distribution of basic soil characteristics and taxonomic status of sodic soils

Afforestation, settled before 60–90 years and adjacent solonetzic grasslands, representing the natural vegetation cover were compared in this study based on their basic soil characteristics (pH, CaCO3 content, soil organic carbon (SOC), and exchangeable sodium percentage (ESP)) up to 2 m depth. The assumption was that the plantings of arbour vegetation can change soil characteristics of sodic soils not only in superficial layers but even in larger depths. Grasslands and forest soils were compared by standardised depths. Afforested soils showed lower pH in the depth at 0–100 cm, and slightly higher SOC content in subsoil (20–100 cm). CaCO3 content was significantly different (higher) only at the depth of 50–100 cm in afforested soils. Remarkable differences in ESP values were measured. Afforestation had in almost every layer (0–20, 20–50, 50–100 and 150–200 cm) a significant lower ESP value than grassland soil samples from the same depths. As the value of the ESP is relevant from soil classification purposes as well, the leaching of sodium also can change the taxonomic status of the soils from soils with natric horizon, to soils with Sodic or Bathysodic qualifiers.

Simplified Evaluation of Salt Affected Soils Using 1:5 Soil–Water Extract

ABSTRACT Because of the global increase in salt-affected soils, rapid and cost-effective remediations and easily measurable soil salinity evaluations are required. Soil salinity, through EC, and soil sodicity through exchangeable sodium percentage values, were predicted using a 1:5 soil-water extract. To determine the differences of soil salinity evaluations between arid regions, 48 soil samples (Inceptisols and Entisols) from China and 120 soil samples (Aridisol) from Sudan were used in this study. Positive correlations between the EC of a soil saturation extract and EC, exchangeable sodium percentage, and sodium adsorption ratio of a 1:5 soil-water extract were observed in all the soil samples. A simplified evaluation of salt-affected soils was possible using these relational expressions. Although the correlations differed by region, each correlation was strong. This was due to the differences in soil clay content and mineral composition between China and Sudan, but it also affected the salt content and composition in the soils. In addition, a strong correlation of soil salinity evaluations between saturated extract method and 1:5 soil–water extract method was observed even in the same area even when the salt content varied. Since accumulated salts were affected by the salt composition in irrigation water used in each region, soil salinity, and soil sodicity could be evaluate via simplified method based on the irrigation area. This results can be useful for farmland management in arid regions.

Melon cultivation irrigated with saline waters promote chemical alterations in an acrisol

The objective of the present study was to evaluate the salinization process and the changes in the chemical properties of an Acrisol cultivated with melon irrigated with water of different saline concentrations. The experiment was carried out in the field conditions using the experimental design of randomized blocks, arranged in split-plot. The plots were composed of salinity levels of irrigation water, expressed in terms of water electrical conductivity (ECw): 0.54; 1.48; 2.02 dS m-1; and the sub-plots for melon cultivars: Sancho and Medellín (Toad Skin), Mandacaru (Yellow), Nectar (Galia) and Sedna (Cantaloupe). Soil samples were collected at the beginning and end of the crop cycle to evaluate the changes in the physical-chemical properties of the soil. The electrical conductivity of saturation extract in the soil profile varied for each cultivar, observing high salinity values in soils with cultivars with lower water demand (Sedna and Nectar). The salinity of the soil was lower than the electrical conductivity of the irrigation water in the treatments with high values of ECw. The soil pH values showed little reaction in relation to the initial values. The exchangeable sodium percentage values were approximate twice the sodium adsorption ratio of the saturation stratum.

Structural stability and hydraulic characteristics of soils irrigated for two decades with waters having residual alkalinity and its neutralization with gypsum and sulfuric acid

Degradation of soils due to sodification is now widespread in arid and semiarid areas irrigated with groundwater having residual alkalinity. We monitored the changes in soil physical, chemical, and hydraulic characteristics of a sandy loam soil irrigated for the last two decades with two types of alkali waters (AW1, AW2) having similar salts (total electrolyte concentration, TEC=30 me L−1) and sodium adsorption ratio (SARiw 10 mmol L−1) but varying in residual sodium carbonate, RSC (5 me L−1 in AW1 and 10 me L−1 in AW2), and when latter irrigation water (AW2) was ameliorated to neutralize RSC equivalent to 5 me L−1 with either sulfuric acid (AW2 +SA) or gypsum (AW2 +GYP). Deterioration of overall soil quality was evidenced by increased bulk density and penetration resistance, decreased aggregate stability, increased soil pH and sodicity, and decline in accumulation of soil organic carbon, especially with AW2. Exchangeable sodium percentage (ESP) build up ranged between 2.1 and 3.3 times SARiw. The steady infiltration rate (IR) in soil irrigated with good quality water, GQW (Electrical conductivity, ECiw=0.52dSm−1; RSC=1.2 me L−1), was 5.4 mm h−1 (IR-GQW) while it reduced to 2.2, 1.0, 1.7, and 1.8 mm h−1 with AW1, AW2, AW2 +SA, and AW2 +GYP, respectively. The adverse effects of soil sodification exacerbated with rainwater (RW; simulated with deionized water, EC <0.03dSm−1) infiltration, further reducing the IR to 1.1, 0.7, 1.4, and 1.0 mm h−1 for AW1, AW2, AW2 +SA, and AW2 +GYP, respectively. The recovery of IR was only a little (2–11%) when RW was replaced with respective irrigation waters, even when the surface 5 cm was tilled to break soil crusts (ST). This indicates permanent damage to soil structure and water transmission characteristics through the development of sub-soil throttles with moved-in clays. Power functions described the surface soil ESP to control IR (R2 =0.53–0.83 **), and the ESP values for 0.25 IR-GQW were 24.5, 15.8, 17.4, 14.5 and 14.4 for IW (respective irrigation waters), RW, IW-RW, RW-IW, and RW-IW-ST-IW sequences of infiltration events, respectively. There were considerable reductions in post-infiltration water storage in the soil profile, and a slowed down redistribution of infiltrated water were also observed. The neutralization of RSC with either sulfuric acid or gypsum improved the hydro-physical properties; the impact of gypsum being slightly better especially in improving soil stability characteristics.

Sustainable effects of gypsum from desulphurization of flue gas on the reclamation of sodic soil after 17 years

Reclamation of saline–sodic soils with gypsum from the desulphurization of flue gas (FGD) is a recently developed technique. However, limited information is available on the long‐term effects of FGD gypsum in agricultural fields. This study evaluated the effects of FGD gypsum on soil physical and chemical properties and heavy metal concentrations after 17 years. Established in 2001, the study site on the Tumochuan Plain of Inner Mongolia, China, has a sandy loam soil. The experimental field was divided into three classes characterized by small, medium and large exchangeable sodium percentage (ESP) values before the experiment. Based on the initial soil ESP values (6.1–20, 20–30 and 30–78.4%, respectively), FGD gypsum was applied once at rates of 20.9, 30.6 and 59.3 t ha−1 to the small‐, medium‐ and large‐ESP classes, respectively. Compared with the control plots, the treated plots showed decreases in soil pH of 9.8 and 7.5% and decreases in ESP of 52.7 and 46.6% at the 20–40‐cm and 40–60‐cm depths, respectively. The treated plots showed remarkable decreases in electrical conductivity at the 20–60‐cm depth in the small‐ESP class, but moderate increases at the 0–20‐cm depth in the medium‐ and large‐ESP classes. The dissolved salt composition changed, with substantially larger Ca2+ and SO42− but smaller CO32− + HCO3− concentrations in the treated plots than in the control plots. The treated plots showed increases in the macroaggregate fractions (&gt;250 μm) and decreases in the silt–clay fractions (&lt;53 μm). There were no significant differences in the heavy metal (Cd, Hg, As, Pb, Cr, Cu, Zn and Ni) concentrations among the plots; thus, the use of FGD gypsum in agricultural fields is safe. The beneficial effects of FGD gypsum on the reclamation of sodic soils remained and were concentrated deeper in the soil after 17 years.Highlights Limited information is available on the lasting effects of FGD gypsum in agricultural fields. The long‐term effects of FGD gypsum on soil physicochemical properties are reported for the first time. The beneficial effects of FGD gypsum on soil reclamation extended to the 20–60‐cm soil layers. The use of FGD gypsum in agricultural fields was safe, and the effects lasted many years.

Long-term simulation of some soil chemical properties under continuous wheat cultivation irrigated with waters of different qualities

The use of low-quality waters for irrigation in arid and semiarid regions is increasing due to the shortage of good-quality water supplies. Geochemical simulations are cost-effective ways to determine the suitable strategies for sustainable water and soil management. In the first step of this study, the combination of one-dimensional solute transport equation and cation exchange model in PHREEQC was used to predict breakthrough curves of the exchangeable sodium percentage (ESP) of nine soil columns during the leaching with 20 pore volumes of a solution with sodium adsorption ratio (SAR) of 10. In the second step, the trend of changes in solution and exchangeable phases of a non-sodic agricultural soil was simulated over 20 years of continuous wheat cultivation irrigated with waters of different qualities. The graphical and statistical comparison (RMSE values ranged from 0.36 to 0.95) between experimental and predicted results showed that the geochemical simulations in the first step were successful. Simulation results of the second step indicated that the soil ESP decreased from 10.1 to 5.6% after a 20-year consecutive application of water with SAR 2.5, while the long-term use of irrigation waters with SAR 10 and SAR 40 increased the final soil ESP to 27.8 and 88.5%, respectively. In the case of application of irrigation water with SAR 10, the final ESP values of wheat residues-, gypsum-, and calcite-amended soils were 18.5, 16.9, and 20.2% which were less than that obtained for control soil.

English

Considerable area of land is becoming unproductive every year because of salinity and sodicity in lowlands of Ethiopia. For sound land use and irrigation water management, it is a paramount important to know the chemical composition of soils and irrigation water. Therefore, the study was aimed to evaluate the physicochemical properties of soils and irrigation water of Tendaho sugarcane production farm, located in north-eastern rift valley of Ethiopia. Depth wise soil samples from 4 different locations and 1 irrigation water sample from 2 sub-samples (from delivery head and the influent river) were collected. The result of the particle size analysis indicates that majority of the soils were heavily textured. The pH of the soil in all parts of the study area ranged from 7.8 to 8.6. Electrical conductivity readings of most of the studied soil profiles were high. Exchangeable sodium percentage values showed actual sodium toxicity problem (ESP>15) in the first profile and potential sodium toxicity (ESP>1) in the remaining profiles. On the other hand, the irrigation water has a low sodicity hazard; however, pH (7.65) and EC (0.654 dS/m) values clearly indicated that it is moderately alkaline and saline. Hence, coupled with water and soil analysis results, there will be a potential danger of sodicity and actual salinity development in the intended irrigation scheme. Thus, selection of crop type and proper irrigation methods should be designed for sustainability of soil productivity in the study area. Key words: Salt affected soil, irrigation water, characterization and classification, sugarcane production.

Monitoring changes in soil salinity and sodicity to depth, at a decadal scale, in a semiarid irrigated region of Australia

Soil salinity and sodicity are two of the most limiting constraints for agriculture in arid and semiarid landscapes, but long-term studies are scarce, and most solely focus on the topsoil. This study monitors the change in soil electrical conductivity (EC) and exchangeable sodium percentage (ESP) to 1.2 m depth with bivariate linear mixed models between 2002 and 2015 in a semiarid, irrigated cotton-growing region of south-west New South Wales, Australia. In this work, the impacts of shifts in rainfall, variability of irrigation water quantity and quality, and agricultural land uses, on soil salinity and sodicity are analysed. The study area possessed generally low levels of soil salinity, and shifts in EC were detected over time, but only isolated areas of the various sampling depths experienced statistically significant changes in EC. Some areas under irrigated cotton production experienced a desalination trend, whereas soil EC under irrigated perennial horticulture increased over time. This increase was attributed to the use of fertilisers that contain salts, and the varying quantity and quality of applied irrigation water. Sodicity was low to moderate in the upper 0.5 m of the soil profile but high in deeper layers, with a trend of increasing soil sodicity through time. Most of the statistically significant increases in ESP occurred in areas under irrigated cotton and horticulture, with this likely due to the continued addition of sodium to the soil system. This study also demonstrates that visible near infrared spectroscopy can be used in to predict soil ESP values to reasonable accuracy.

Modeling of soil exchangeable sodium percentage using easily obtained indices and artificial intelligence-based models

Salinization and alkalization of land resources are the major obstacles to their optimal usage in many arid and semi-arid regions of the world, including Iran, since potential evapotranspiration is more noteworthy than precipitation in these areas. The amount of water that enters the soil is low and this results in salt accumulation in soils, which makes the soil infertile. Moreover, existence of salts, for example, sodium, in soils causes dispersion of soil particles and soil degradation, and intensifies soil erosion too. Monitoring exchangeable sodium percentage (ESP) variability in soils is both time-consuming and costly. However, in order to estimate the amounts of amendments and land management, it is necessary to know ESP variation and values in sodic or saline and sodic soils. Thus, introducing a method, which utilizes easily obtained indices to estimate ESP indirectly is more optimized and economical. Input and output data, i.e., ECe (dS m−1), clay (%), pH and ESP (%) were collected and measured from 100 soil samples in light of a stratified random sampling from Mashhad Plain, Khorasan-e-Razavi Province, Northeast Iran. This study aims to propose some models to estimate ESP by easily obtained properties of soil. In this regard, the efficiency of artificial intelligence-based (AI) models (i.e., Artificial Neural Network, ANN, and Adaptive Neuro-Fuzzy Inference System, ANFIS) was investigated and compared. Accuracy results showed that owing to highest R2 and the lowest mean square error (MSE), ANFIS model predictions were superior to the MLP model for indirect estimation of soil exchangeable sodium percentage.

Sodic Soil Reclamation in a Semi-Arid Region Involving Organic Amendments and Vegetative Remediation by Casuarina equsetifolia and Erianthus arundinaceus

In arid and semi-arid regions of the world, certain farming practices and land management have resulted in saline/sodic soils. An experimental study was carried out in a semi-arid region of Southern India, where excess irrigation in the uplands has caused sodic soils in low-lying areas. In order to alleviate the sodicity problem, a combined approach involving application of organic manure, green manuring with Sesbania rostrata and subsequently vegetative remediation by plantation of Casuarina equsetifolia and Erianthus arundinaceus clones was attempted. The use of Erianthus arundinaceus in the integrated treatment along with other amendments is first of its kind in the region and about 20 % of reduction in Exchangeable Sodium Percentage (ESP) was achieved over the initial values. The initial values of ESP in the control plot as wells as treated plot at three different depths varied between 44 and 42.3 %, and after treatment with organic amendments followed by Casuarina and Erianthus plantations, the ESP was reduced to 35–36.5 %. Vegetative remediation in combination with other amendments considerably improved the major and micro nutrients besides nurturing the soil micro-organisms and enzyme activity. At the end of the experiment, about 81 % - 92 % survival rate of the crops was obtained. The cost-benefit ratio analysis based on the market demand for pulpwood ranged between 1:1.75 and 1:2.05. Overall, the experimental results ascertained that the integrated approach for reclamation of sodic soil has been found to be an efficient, cost effective and environmentally sound strategy for semi-arid regions.

Predicting ESP and SAR by artificial neural network and regression models using soil pH and EC data (Miankangi Region, Sistan and Baluchestan Province, Iran)

Monitoring exchangeable sodium percentage (ESP) and sodium adsorption ratio (SAR) variability in soils is both time-consuming and expensive. However, in order to estimate the amounts of amendments and land management, it is essential to know ESP and SAR variations and values in sodic or saline and sodic soils. Thus, presenting a method which uses easily obtained indices to estimate ESP and SAR indirectly is more optimal and economical. Input data of the current research were 189 soil samples collected based on a regular networking approach from Miankangi region, Sistan plain, Iran. Then, their physicochemical properties were measured. Results showed that SAR = 3.8 × ln(EC) + 22.83 × ln(pH) – 44.37, (R2 = 0.63), and ESP = 3.98×ln(EC) + 36.88(pH) – 56.98 (R2 = 0.78) are the best regression models for estimating SAR and ESP, respectively. Moreover, multilayer perceptron (MLP), which explains 95–97% of parameters of soil sodicity using EC and pH as inputs, was the best neural network model. Therefore, MLP could be applied for ESP and SAR evaluation with high accuracy in the Miankangi region.

Influence of Water Quality on Exchange Phase-Solution Phase Behavior of Texturally Different Salt-affected Soils

The influence of total electrolyte concentration (TEC) and sodium adsorption ratio (SAR) of water on ESR-SAR relationships of normal clay loam, saline silty loam and calcareous sodic loam soils was studied in a laboratory experiment. Twelve solutions, encompassing three TEC levels viz., 25, 50, and 100 me L−1 and four SAR levels viz., 5, 10, 20 and 30 mmol1/2 L−1/2 were prepared to equilibrate the soil samples using pure chloride salts of calcium, magnesium and sodium at Ca: Mg = 2: 1. The SAR of equilibrium solution decreased as compared to the equilibrating solution and more so in waters of low salt concentration and low SAR. At all electrolyte concentration, SAR values were not attained to the equilibrium solution because of addition of Ca and Mg from mineral dissolution or supply of Ca and Mg from exchange sites. At higher TEC levels, considerable increase in exchangeable sodium percentage (ESP) was observed when it was correlated for anion exclusion and more so in calcareous sodic loam followed by saline silty loam and normal clay loam soils. Irrespective of TEC, the exchangeable sodium in all the soils increased by 2.1 to 3.8-fold and irrespective of SAR, it increased by about 1.1 to 2.1-fold, respectively. So, there is a positive interaction of TEC and SAR in sodification of soils. A positive interaction of TEC and SAR influenced the ESP build-up and CEC and silt + clay content played a major role in the visual disparity in sodification of these soils. Gapon's selectivity coefficient values were perceptible in the order of calcareous sodic loam > saline silt loam > normal clay loam. This indicates the preference of normal clay loam soils for Ca2+ + Mg2+ than that of Na+ on the exchange complex, whereas loam soil exhibited high affinity for sodium. Regression coefficient of ESR-SAR relationships was maximum for sodic loam followed by saline silty loam and normal clay loam soil. The exchange equilibrium was strongly affected by TEC of the solution phase. Variation in soil pH was gradual with respect to TEC and SAR of equilibrating solution and a sharp change was observed. At a fixed TEC, critical ESP values were observed calcareous sodic loam followed by saline silt loam and normal clay loam. On the other hand, SAReq needed for critical ESP built-up was in the order of calcareous sodic loam > saline silt loam > normal clay loam. This may be because of dissolution of calcium bearing minerals in calcareous sodic loam; and wash out of calcium and magnesium from the exchange sites for saline silt loam soil.

Efficiency of quicklime in reducing the swelling potential of pulverized expansive shale, Northern Jeddah, Saudi Arabia

Expansive shale has been found extensively all over the world, especially in tropical and sub-tropical regions. The ground heave that results from shale swelling potential is a multi-factorial phenomenon. Remarkably, the expansive shale of Saudi Arabia varies considerably due to variations in its ancient environmental climatic conditions. The studied shale of Bathan Formation at Al-Rehaili northeastern Jeddah is considered a problematic expansive material and classified as clayey shale of high plasticity (CH). Clay mineral species of these lacustrine sediments are composed mainly of smectite, kaolinite, and smectite-illite mixed layered. Exchangeable sodium percentage values of the Bathan Formation, northern Jeddah are very low. Addition of quicklime (up to 3 %) decreases consistency limits. The destructive effect of quicklime addition (up to 3 %) on the swelling potentiality of these clayey-rich sediments is due to the formation of highly swell ettringite. Mechanical properties, such as unconfined compression strength, have been improved due to the cementation effect of lime as well as the creation of new crystalline compounds such as calcium silicates and ettringite. Adding quicklime percent should not exceed 3 % to prevent increasing pH value and to avoid formation of ettringite which has higher ability to swell.