Soil Exchangeable Sodium Percentage Research Articles

Ameliorative Effect of Different Amendments on Nutrients Availability in Sodic Soils

A pot house experiment was conducted at the Net House, Regional Research Station, AAU, Anand during rabi season of 2018-19 on Wheat (GW-496) as a indicator crop. Total four amendments i.e. A0(control), A1(Gypsum @ 50% GR), A2(Vermi-compost @ 4.0 t ha-1) and A3 (sulphur @ 50 kg ha-1) and six soils type (S1 to S6) were selected under Factorial CRD. Pot study results indicated that the soil amendments significantly decreased the pH, EC and ESP of sodic soils. The order of decrease in pH of sodic soils from 8.75 to 7.89 by application of amendments remained as: vermin-compost > sulphur > gypsum. The EC of sodic soils significantly decreased due to application of vermin-compost and gypsum by 20.48% and 10.84%, respectively over control. The application of vermin-compost, gypsum and sulphur significantly lowered down Exchangeable Sodium Percentage (ESP) from 18.45 to 12.44, 13.00 and 13.57, respectively, and the effect of gypsum was found at par with sulphur in decreasing soil ESP. Application of vermin-compost (4.0 t ha-1) significantly influenced CEC (28.28 Cmol (P+) kg-1) over control (no amendment). Irrespective of amendments, soil S5 recorded the highest pH (8.39), EC (0.92 dSm-1), ESP (16.48) and the lowest was in soil S6 (pH 7.99, EC 0.64 dSm-1). The interaction of soil x amendment treatments showed significant effects on pH, EC and ESP of sodic soils. The application of amendments showed significant effect on available nutrients in soil after harvest of wheat and the highest OC (0.73%), available P2O5 (65.71 kg ha-1), available K2O (207.1 kg ha-1) content in soil was recorded when vermin-compost applied at 4.0 t ha-1 followed by sulphur at 50 kg ha-1 and gypsum at 50% GR but available S (16.33 mg kg-1) was recorded the highest due to sulphur application at 50 kg ha-1 followed by gypsum and vermi-compost.

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.

Impacts of various amendments on the microbial communities and soil organic carbon of coastal saline-alkali soil in the Yellow River Delta.

The utilization of industrial and agricultural resources, such as desulfurization gypsum and straw, is increasingly favored to improve saline alkali land. However, there is still a lack of comprehensive study on the mechanism of organic carbon turnover under the conditions of desulfurization gypsum and straw application. We studied the changes in soil chemical performance, microbial diversity, and microbial community structure in soils with the addition of various levels of straw (no straw, S0; low straw, Sl; medium straw, Sm; and high straw, Sh) and gypsum (no gypsum, DG0; low gypsum, DGl; and high gypsum, DGh) in a 120-day incubation experiment. The bacterial and fungal community richness was higher in the SmDGl treatment than in the SmDG0 treatment. The microbial community evenness showed a similar pattern between the SmDGl and SmDG0 treatments. The combination of the straw and desulfurization gypsum treatments altered the relative abundance of the main bacterial phyla Bacteroidetes and Firmicutes and the dominant fungal class Sordariomycetes, which increased with the enhancement of the SOC ratio. The combination of the straw and desulfurization gypsum treatments, particularly SmDGl, significantly decreased the soil pH and exchangeable sodium percentage (ESP), while it increased the soil organic carbon, microbial biomass carbon, and activities of soil enzymes. Improvement in the soil salinization environment clearly drove the changes in bacterial α-diversity and community, particularly those in the soil carbon fractions and ESP. In conclusion, these findings provide a strong framework to determine the impact of application practices on soil restoration, and the information gained in this study will help to develop more sustainable and effective integrated strategies for the restoration of saline-alkali soil.

Comparison of the effectiveness of mined and by-product South African gypsums and other calcium sources for soil sodicity remediation

Studies evaluating the effectiveness of South African gypsum sources are scarce or outdated because of newly introduced products, such as granulated and liquid gypsums. The efficacy of calcium (Ca) nitrate and micro-fine (MF) calcitic limes in comparison to gypsums has also never been evaluated. The aim of this study was to compare the effectiveness of mined and by-product gypsums and other Ca sources in terms of soil sodicity remediation and saturated hydraulic conductivity (Ksat) improvement. In a controlled laboratory study, 12 mined and by-product gypsums sources, MF calcitic limes and calcium nitrate were surface-applied to a sodic, sandy loam soil to achieve an exchangeable sodium percentage (ESP) of 5%. The soils received 300 mm simulated rainfall, and then soil chemical properties and Ksat were determined. Finer by-product gypsum sources (particularly liquid and flue gas desulphurisation (FGD) gypsums) exhibited faster dissolution rates and superior performance in lowering soil ESP to 4.2–4.7% and pH by 0.5–0.7 units compared to Class A mined gypsums (ESP 9.0–11.1% and 0.2 pH units). Only the liquid, phospho-, FGD gypsums and calcium nitrate significantly increased soil hydraulic conductivity (123–130%) compared to the control. The MF calcitic limes had no effect on the sodic soil properties.

Predicting Dynamics of Soil Salinity and Sodicity Using Remote Sensing Techniques: A Landscape-Scale Assessment in the Northeastern Egypt

Traditional mapping of salt affected soils (SAS) is very costly and cannot precisely depict the space–time dynamics of soil salts over landscapes. Therefore, we tested the capacity of Landsat 8 Operational Land Imager (OLI) data to retrieve soil salinity and sodicity during the wet and dry seasons in an arid landscape. Seventy geo-referenced soil samples (0–30 cm) were collected during March (wet period) and September to be analyzed for pH, electrical conductivity (EC), and exchangeable sodium percentage (ESP). Using 70% of soil and band reflectance data, stepwise linear regression models were constructed to estimate soil pH, EC, and ESP. The models were validated using the remaining 30% in terms of the determination coefficient (R2) and residual prediction deviation (RPD). Results revealed the weak variability of soil pH, while EC and ESP had large variabilities. The three indicators (pH, EC, and ESP) increased from the wet to dry period. During the two seasons, the OLI bands had weak associations with soil pH, while the near-infrared (NIR) band could effectively discriminate soil salinity and sodicity levels. The EC and ESP predictive models in the wet period were developed with the NIR band, achieving adequate outcomes (an R2 of 0.65 and 0.61 and an RPD of 1.44 and 1.43, respectively). In the dry period, the best-fitted models were constructed with deep blue and NIR bands, yielding an R2 of 0.59 and 0.60 and an RPD of 1.49 and 1.50, respectively. The SAS covered 50% of the study area during the wet period, of which 14 and 36% were saline and saline-sodic soils, respectively. The extent increased up to 59% during the dry period, including saline soils (12%) and saline-sodic soils (47%). Our findings would facilitate precise, rapid, and cost-effective monitoring of soil salinity and sodicity over large areas.

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

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

Prediction of Soil Salinity/Sodicity and Salt-Affected Soil Classes from Soluble Salt Ions Using Machine Learning Algorithms

Salt-affected soils are related to salinity (high content of soluble salts) and/or sodicity (excess of sodium), which are major leading causes of agricultural land degradation. This study aimed to evaluate the performances of three machine learning (ML) algorithms in predicting the soil exchangeable sodium percentage (ESP), electrical conductivity (ECe), and salt-affected soil classes, from soluble salt ions. The assessed ML models were Partial Least-Squares (PLS), Support Vector Machines (SVM), and Random Forests (RF). Soil samples were collected from the High Valley of Cochabamba (Bolivia). The explanatory variables were the major soluble ions (Na+, K+, Ca2+, Mg2+, HCO3−, Cl−, CO32−, SO42−). The variables to be explained comprised soil ECe and ESP, and a categorical variable classified through the US Salinity Lab criteria. According to the model validation, the SVM and RF regressions performed the best for estimating the soil ECe, as well as the RF model for the soil ESP. The RF algorithm was superior for predicting the salt-affected soil categories. Soluble Na+ was the most relevant variable for all the predictions, followed by Ca2+, Mg2+, Cl−, and HCO3−. The RF and SVM models can be used to predict soil ECe and ESP, as well as the salt-affected soil classes, from soluble ions. Additional explanatory features and soil samples might improve the ML models’ performance. The obtained models may contribute to the monitoring and management of salt-affected soils in the study area.

Improved prediction of soil exchangeable sodium percentage (ESP) using wavelet

In Australia, the soil is considered sodic when the top meter has an exchangeable sodium percentage (ESP) greater than six (6%). Sodicity is a natural feature of Queensland, particularly the case in northeast Queensland where sugarcane is grown. To ameliorate sodicity effectively, a digital soil mapping (DSM) approach with digital data (e.g. elevation, gamma-ray [γ-ray] spectrometry, and soil apparent electrical conductivity [(ECa)]) could be used. However, when a relationship between digital and soil data does not exist, wavelet transformation could be employed. Firstly, we aim to see if digital data, alone or in combination, can be used to predict topsoil (0–0.3 m) ESP using a linear mixed model (LMM). Secondly, we decompose the digital data using wavelet transform into components (i.e. detail [D] and approximate [A]) at different scales (i.e. 10, 20, 40, and 80 m). We then aim to develop an LMM to predict topsoil ESP using D or A or in combination. Results show that prediction of topsoil ESP by LMM using raw digital data either alone (Lin’s = 0.27) or in combination (0.37) was poor (Lin’s < 0.65). The prediction of topsoil ESP by LMM using D components alone was unsatisfactory at small scales, however, moderate agreement (0.65 < Lin’s < 0.8) was achieved at scales of 80 m (0.66). In combination with D and A, a moderate agreement was achieved at 40 m (0.71) and a good agreement at 80 m (0.85). When considering the decomposed digital data individually, and at the same scale, the prediction of topsoil ESP using decomposed ECa (0.56) was better than γ-ray (0.38). Interestingly, the decomposed elevation cannot be used individually to predict ESP. However, adding decomposed elevation to γ-ray (0.58) and ECa (0.67), the prediction of ESP was enhanced. The best prediction of ESP was achieved using all decomposed data at 80 m (0.85). However, further work in validation would be required to confirm topsoil ESP was non-sodic (<5 %) and where it was deemed to be strongly sodic (>20 %) as these were not measured. Nevertheless, the DSM offers the real prospect of applying the six-easy-steps ameliorant management guidelines (Schroeder et al., 2006) to apply suitable rates of gypsum, including 2 t/ha for sodic (ESP; 5–10 %), 4 t/ha for moderately (10–15 %) and 6 t/ha for strongly (>15 %) sodic topsoil.

Reinforced soil salinization with distance along the river: A case study of the Yellow River Basin

Clarifying the relationship between salt-affected soils and their adjacent river systems is critical to address the challenges posed by soil salinization on agricultural production. Among the various biophysical and land management factors linked to soil salinization, few studies have investigated the importance of the distance along the river. Based on the Hetao Irrigation District of the Yellow River Basin, we collected 5314 soil samples and analyzed 17 soil parameters to explore the relationship between salt-affected soils and their distance along the river. Soil salinization was reinforced by the distance along the river, as a trade-off between soil ion accumulation and nutrient regulation. Soil total water-soluble salt content increased by 16.4 mg kg−1 every kilometer, likely due to ions leaching from the soils upstream and partially accumulating in the soils downstream, especially for Cl-, SO42-, and Na+. Greater input and less solubility of Ca2+ based soil amendments, phosphorus fertilizers, and organic materials on the less salt-affected soils upstream may explain the declines in soil Ca2+, available phosphorus, and soil organic matter with distance along the river. With every kilometer along the river, soil exchangeable sodium and cation exchange capacity increased by 8.89 × 10−4 and 1.26 × 10−2 cmol kg−1, respectively, which led to an increase in soil exchangeable sodium percentage by 9.59 × 10−5. The increase in soil exchangeable sodium along the river was mainly due to Na+ accumulation, while soil cation exchange capacity was regulated by soil organic matter and total nitrogen. Soil pH increased by 1.21 × 10−3 per kilometer along the river, associated with the decrease of soil organic matter. Future saline soil amelioration and reutilization initiatives at regional scales may be improved by accounting for the changes in soil physicochemical properties resulting from the distance along the river.

Water regime enhances the effects of flue gas desulfurization gypsum on the reclamation of highly saline‐sodic soil

AbstractFlue gas desulfurization (FGD) gypsum‐based reclamation of saline‐sodic soil has been widely used in the Songnen Plain of China, but its reclamation effect depends on the water regime. A pot experiment was conducted to identify the optimal water regimes for reclaiming a highly saline‐sodic soil [pH, electrical conductivity (EC) and exchangeable sodium percentage (ESP) were 10.4, 5.5 dS m‒1 and 68.1%, respectively] by using FGD gypsum. Three water regimes with drainage times [irrigation amounts of 3‐, 5‐, and 7‐times the soil pore volume (PV)] were selected and FGD gypsum was added to a portion of the regimes before the final drainage operation. Then the saline‐sodic parameters of drainage and soil were measured and analyzed. Na+, Cl−, HCO3−, and SO42− were the main ions in the drainage of all the treatments. With the increase in drainage times, the water regime without FGD gypsum notably decreased soil EC by 17.8%–52.0%. In contrast to the FGD gypsum treatment, the water regime failed to decrease the soil ESP. FGD gypsum application with three drainage times had optimal reclamation with reductions in soil pH and ESP of 0.5–2.3 units and 5.1%–20.1%, respectivley. But the associated water consumption was more than 40% higher than that of one‐ or two‐drainage operations. In terms of water reduction (irrigation volume was 5 times PV), sodicity reduction and salt removal (soil pH, ESP, and EC were reduced by 1.7 units, 12.3%, and 1.12 dS m−1), FGD gypsum application with two‐time drainage could be a more suitable measure to reclaim highly saline‐sodic soil.

Straw and nitrogen amendments improve soil, rice yield, and roots in a saline sodic soil

Straw return can improve the physical properties and nutrient status of the soil. However, there are few studies on straw return coupled with nitrogen (N) fertilizer for rice planting in saline sodic areas. Therefore, we conducted a two-year field experiment to evaluate the effects of straw management (retention or removal) with N fertilizer (0, 90, 180, 270 and 360 kg N ha−1) on soil properties, root characteristics, rice yield and N use efficiency in a saline sodic rice growing area. The results showed that straw return significantly reduced soil bulk density, pH, soil electrical conductivity of saturated paste extraction (ECe), exchangeable sodium (ENa+), exchangeable sodium percentage (ESP), and also significantly increased soil organic matter and cation exchange capacity (CEC). Compared with straw removal, straw return reduced soil pH, ECe, ENa+, and ESP by 2.97%, 10.90%, 8.95%, and 13.78%, respectively. At the same N level, straw retention reduced rice root morphology and root vigor at mid-tillering and panicle initiation, but N fertilizer was able to alleviate root inhibition by straw return. Straw return improved root morphology and root vigor in mid and late rice growth and promoted nutrient uptake. Compared with straw removal, the agronomic efficiency nitrogen and partial factor productivity were significantly increased by 13.97% and 4.59%, respectively, in the straw return treatment. With or without straw retention, rice yield increased and then decreased with increasing N fertilizer application rate, and was maximum at 270 kg N ha−1. Compared to straw removal, rice yield was significantly increased by 4.37% (2020) and 7.17% (2021) for straw return treatments, respectively. Meanwhile, straw return can reduce mineral N fertilizer inputs by about 36–43% without affecting rice yield. Under straw return conditions, soil characteristics, root characteristics, and rice yield were optimal at 270 kg N ha−1. Our results suggest that straw return combined with nitrogen fertilization may be a promising management practice to reduce mineral N application without loss of rice yield in saline sodic soils. Among them, straw return combined with 270 kg N ha−1 was most effective in the early stages of straw return in saline sodic rice growing areas.

Application of Silica Nanoparticles in Combination with Two Bacterial Strains Improves the Growth, Antioxidant Capacity and Production of Barley Irrigated with Saline Water in Salt-Affected Soil.

Exploitation of low-quality water or irrigation of field crops with saline water in salt-affected soil is a critical worldwide challenge that rigorously influences agricultural productivity and sustainability, especially in arid and semiarid zones with limited freshwater resources. Therefore, we investigated a synergistic amendment strategy for salt-affected soil using a singular and combined application of plant growth-promoting rhizobacteria (PGPR at 950 g ha−1; Azotobacter chroococcum SARS 10 and Pseudomonas koreensis MG209738) and silica nanoparticles (SiNPs) at 500 mg L−1 to mitigate the detrimental impacts of irrigation with saline water on the growth, physiology, and productivity of barley (Hordum vulgare L.), along with soil attributes and nutrient uptake during 2019/2020 and 2020/2021. Our field trials showed that the combined application of PGPR and SiNPs significantly improved the soil physicochemical properties, mainly by reducing the soil exchangeable sodium percentage. Additionally, it considerably enhanced the microbiological counts (i.e., bacteria, azotobacter, and bacillus) and soil enzyme activity (i.e., urease and dehydrogenase) in both growing seasons compared with the control. The combined application of PGPR and SiNPs alleviated the detrimental impacts of saline water on barley plants grown in salt-affected soil compared to the single application of PGPR or SiNPs. The marked improvement was due to the combined application of PGPR and SiNPs, which enhanced the physiological properties (e.g., relative chlorophyll content (SPAD), relative water content (RWC), stomatal conductance, and K/Na ratio), enzyme activity (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX)), and yield and yield-related traits and nutrient uptake (N, P, and K) of barley plants. Moreover, the Na+ content, hydrogen peroxide (H2O2) content, lipid peroxidation (MDA), electrolyte leakage (EL), and proline content were reduced upon the application of PGPR + SiNPs. These results could be important information for cultivating barley and other cereal crops in salt-affected soil under irrigation with saline water.

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.

Influence of environmental-friendly bio-organic ameliorants on abiotic stress to sustainable agriculture in arid regions: A long term greenhouse study in northwestern Egypt

The problem of soil salinity is rapidly increasing, with more than 950 million hectares affected by salinity stress (Arora et al., 2017). The amelioration of saline-sodic soils using chemical ameliorates could increase CO2 emissions and soil degradation. Therefore, amending saline-sodic soil with environmentally friendly bio-organic ameliorants such as brewer's spent grain (SG) and Azospirillum (A. brasilense) bacteria could represent a safe and cheaper approach compared to other organic (compost; CT) and mineral fertilizers. Under greenhouse conditions, maize was grown in saline-sodic soil amended with bio-organic ameliorants. Nine treatments were included; (i) SG1 (23.8 t ha−1); (ii) SG2 (47.6 t ha−1); (iii) TC1 (23.8 t ha−1); (iv) TC2 (47.6 t ha−1); (v) injection of A. brasilense with corn seeds (Az); (vi) combination of A. brasilense and SG (Az + SG1); (vii) combination of A. brasilense and compost (Az + TC1); (viii) mineral fertilizers (NPK) and (ix) the control (CK). The results revealed that soil amended with Az and SG2 significantly decreased the exchangeable sodium percentage (ESP) and higher cation exchange capacity (CEC). Compared with the control, the exchangeable sodium (Ex-Na+) concentration was decreased by 53.2 and 49.27%, for Az and Az + SG1 treatments, respectively. The fresh- and dry weight observed for Az + SG1, SG2, and Az treatments were increased compared to TC1, TC2, NPK, and CK treatments. The grain and biological yields were higher in Az + SG1 and SG2 than in TC2, NPK ameliorants, and CK. The bio-organic ameliorants alleviated the abiotic stress, enhance the growth and productivity of corn plants, decrease soil ESP and Na+ content, and enhance soil fertility. In conclusion, the application of SG2 can enhance the growth, and productivity of maize grown under salinity-sodicity stress. Therefore, SG2 and Az + SG1 are recommended for direct application in saline-sodic soil.

Comparative study of pyrochar and hydrochar on peanut seedling growth in a coastal salt-affected soil of Yellow River Delta, China

Biochar (i.e., pyrochar and hydrochar) application is a promising strategy to improve soil quality and productivity. However, the comparison of biochars with different carbonization methods and feedstocks for the plant growth in the coastal salt-affected soil remains limited. In this study, a 30-day microcosmic experiment was conducted to compare the effects of pyrochars and hydrochars derived from reed straw (RPC and RHC) and cow manure (CPC and CHC) on the peanut (Arachis hypogaea L.) seedling growth in a coastal salt-affected soil of Yellow River Delta, China. The results showed that RPC, CHC and CPC significantly elevated fresh shoot weight by 67.77%–89.37%, whereas the RHC amendment showed little effect. The malondialdehyde contents in peanut seedling leaves were significantly declined by 25.28%–35.51% with pyrochar and hydrochar amendments, which might be associated with the enhanced proline contents and K/Na ratios. The stimulation of certain phytohormones (i.e., indole-3-acetic acid, zeatin riboside, gibberellic acid 3) in peanut seedlings with pyrochar and hydrochar amendments might be attributed to the growth enhancement. RPC, CPC and CHC improved the soil properties and fertility such as cation-exchange capacity (CEC), total nitrogen, and available potassium and water holding capacity (WHC) of the coastal salt-affected soil. However, RHC not only significantly decreased soil CEC and WHC, but also increased soil exchangeable sodium percentage. The abundances of soil beneficial bacteria, such as f_Gemmatimonadacea, Sphingomonas, Blastococcus and Lysobacter were enhanced by RPC, CHC and CPC amendments, which were mainly associated with the increased WHC and CEC. Fungal community was less sensitive to pyrochar and hydrochar amendments than bacterial community according to the relative abundance and diversity, and beneficial fungi, such as Oidiodendron and Sarocladium were enriched in the CHC soil. Overall, the application of RPC, CHC and CPC showed greater potentials for the enhancement of peanut growth in a coastal salt-affected soil.

Digital soil mapping and modeling in Loess‐derived soils of Iranian Loess Plateau

The exchangeable sodium percentage (ESP) is the parameter that causes poorly developed soil structure and weak drainage over time, subsequently increasing the dispersion of soil particles, especially silt and clay, which cause soil erosion in Loess-derived soils. The number of 474 soil samples was collected within 0 to 30 cm of soil depth. Five non-linear models named Ridge regression (RidgeR), random forest (RF), support vector regression (SVR), cubist, and generalized boosted regression model (GBM), were considered to link several parameters with ESP in the region of approximately 2,730 ha. The mean square error (MSE), root mean square error (RMSE), and coefficient of determination (R2), were considered to assess the models. The RF and RidgeR algorithms were used to prioritize the variables impacting the ESP. The prediction model for mapping soil ESP had very high accuracy from RidgeR (RMSE = 0.039, R 2 = 0.99), RF (RMSE = 0.257, R2 = 0.97), SVR (RMSE = 0.81, R 2 = 0.544), cubist (RMSE = 0.006, R 2 = 0.99), and GBM (RMSE = 0.426, R 2 = 0.87). The sodium adsorption ratio (SAR) and slope steepness were the most important factors affecting ESP, and slope steepness was recognized as the most effective factor. We also identified that the applied models could simply assess ESP map. In addition, an action plan in different soil horizons, considering erosion and sediment processes, is efficient in controlling runoff at low ESP.

Improved Prediction of Soil Exchangeable Sodium Percentage (Esp) Using Wavelet

Improved Prediction of Soil Exchangeable Sodium Percentage (Esp) Using Wavelet

Assessment of Data-based Models (ANN, ANFIS and SVR) for Estimation of Exchangeable Sodium Percentage (ESP) of Bafra Plain Soils

ABSTRACT The objective of the present study was to estimate the exchangeable sodium percentage (ESP) of the soil from the Bafra plain utilizing easily determined soil characteristics (EC and pH) with the use of artificial intelligence-based models. A total of 448 soil samples were taken from different points of the study area. Artificial neural network (ANN), adaptive neuro-fuzzy inference system (ANFIS) and support vector regression (SVR) models were developed and compared. The present database was randomly divided into training and test data sets (70:30). Coefficient of determination (R2), normalized root mean square error (NRMSE), normalized mean absolute error (NMAE), Nash and Sutcliffe model efficiency (NS) and Akaike’s Information Criterion (AIC) were used as statistical performance indicators to assess the accuracy of the models. Present findings revealed that both ANN (R2 = 0.91, NMAE = 0.21, NRMSE = 0.05, NS = 0.91 and AIC = 191.86) and ANFIS (R2 = 0.91, NMAE = 0.21, NRMSE = 0.05, NS = 0.91 and AIC = 195.51) models had greater general estimation performance than SVR (R2 = 0.89, NMAE = 0.49, NRMSE = 0.08, NS = 0.74 and AIC = 334.57) model. Comparative assessments revealed that ANN and ANFIS approaches could successfully be used in estimation of ESP from EC and pH data. It was concluded based on present findings that artificial intelligence-based techniques could reliably be used in estimation of soil ESP as a promising alternative of traditional approaches.

The Integrated Amendment of Sodic-Saline Soils Using Biochar and Plant Growth-Promoting Rhizobacteria Enhances Maize (Zea mays L.) Resilience to Water Salinity.

The utilization of low-quality water or slightly saline water in sodic-saline soil is a major global conundrum that severely impacts agricultural productivity and sustainability, particularly in arid and semiarid regions with limited freshwater resources. Herein, we proposed an integrated amendment strategy for sodic-saline soil using biochar and/or plant growth-promoting rhizobacteria (PGPR; Azotobacter chroococcum SARS 10 and Pseudomonas koreensis MG209738) to alleviate the adverse impacts of saline water on the growth, physiology, and productivity of maize (Zea mays L.), as well as the soil properties and nutrient uptake during two successive seasons (2018 and 2019). Our field experiments revealed that the combined application of PGPR and biochar (PGPR + biochar) significantly improved the soil ecosystem and physicochemical properties and K+, Ca2+, and Mg2+ contents but reduced the soil exchangeable sodium percentage and Na+ content. Likewise, it significantly increased the activity of soil urease (158.14 ± 2.37 and 165.51 ± 3.05 mg NH4+ g−1 dry soil d−1) and dehydrogenase (117.89 ± 1.86 and 121.44 ± 1.00 mg TPF g−1 dry soil d−1) in 2018 and 2019, respectively, upon irrigation with saline water compared with non-treated control. PGPR + biochar supplementation mitigated the hazardous impacts of saline water on maize plants grown in sodic-saline soil better than biochar or PGPR individually (PGPR + biochar > biochar > PGPR). The highest values of leaf area index, total chlorophyll, carotenoids, total soluble sugar (TSS), relative water content, K+ and K+/Na+ of maize plants corresponded to PGPR + biochar treatment. These findings could be guidelines for cultivating not only maize but other cereal crops particularly in salt-affected soil and sodic-saline soil.

Gypsum and pressmud amelioration improve soil organic carbon storage and stability in sodic agroecosystems

AbstractSalinity–induced land degradation poses a threat to environment and food production globally. Farmers' participatory research (2014–18) was carried out to assess the potential of gypsum (Gyp) and pressmud (PM) in alleviating the sodicity stress, and improvement in soil organic carbon (SOC) pools and its stability in the Trans Indo–Gangetic Plains of India. Intensive rice–wheat cultivation using alkali water increased soil pH, exchangeable sodium percentage (ESP), and bulk density (BD) causing a net depletion in SOC. Gypsum (supplies soluble Ca2+) and pressmud (mobilizes native CaCO3) mediated amelioration (Gyp + PM) significantly decreased soil sodification and compaction, and improved total organic carbon (TOC; 32%–64%) over the unamended control. Higher left–over C for SOC stabilization, crop biomass, and rhizodeposition returned through Gyp + PM significantly improved SOC pools and C sequestration culminating in ~25% yield superiority over the unamended control. Within SOC pools, highest proportion was equally retained in very labile and non–labile C pools. On average, the passive pool contained ~45% of TOC; albeit to a greater contribution through PM followed by Gyp + PM and Gyp. Rice–wheat system yield (RWSY) was positively correlated with SOC pools and indices while negatively correlated with soil pH, ESP, BD, CaCO3, and recalcitrant index. Multiple regression analysis showed stratification ratio, CaCO3, sensitivity index, and BD as key variables for yield prediction under the existing levels of soil sodicity. The key insights suggest ecosystem‐based approach using Gyp + PM in restoring the degraded lands, enhancing crop resilience and system (SOC enrichment and storage) stability, and achieving UN–Sustainable Development Goals related to food security and land degradation neutrality.