Reduction In Exchangeable Sodium Percentage Research Articles

Utilization of marine gypsum as an alternative to mineral gypsum in the reclamation of degraded sodic soil and as a means of enhancing crop productivity

AbstractFor sustainable management of degraded sodic soils, mineral gypsum (GYP) has been widely used, but supplies are limited, industrialization, and urbanization have thwarted its use in agriculture. Therefore, there is a need to develop alternative ameliorants to GYP. We conducted a field experiment on degraded sodic soil (pH‐10.2) using marine gypsum (MG), a waste/by‐product of the edible salt (NaCl) manufacturing process. Based on gypsum requirement (GR) of soil, efficacies of GYP and MG, at equivalent doses, were compared for reclamation of sodic soil using treatments: control, 50 GR GYP, 50 GR MG, 25 GR GYP, 25 GR MG, and 25 GR GYP + 25 GR MG. The results showed a significant decrease in soil pH following appliation of 50 GR MG compared with other treatments. The reduction in exchangeable sodium percentage was found and to be highest (50.78%) in 50 GR MG among all treatments but statistically identical to 50 GR GYP. The net dispersive charge we noted was a minimum of 4.04 cmol kg−1 for 50 GR MG but was on par with 50GR GYP and 25GR GYP + 25GR MG. The presence of MgCl2, NaCl, and KCl as impurities in marine gypsum assisted its dissolution by increasing the ionic strength of solution and facilitated Ca2+ release for exchange reactions. We found the average yield of rice and wheat to be statistically similar for applications of 50 GR MG, 50 GR GYP, and 25 GR GYP + 25 GR MG. Thus, our study suggests that MG could effectively be used as an alternative ameliorant for the reclamation of degraded sodic soil without compromising crop yields, under scarce availability of GYP.

Changes in some chemical properties of saline-sodic soils over time as affected by organic residues: An incubation study

<p>Salinization and sodification of agricultural lands in arid and semi-arid regions of the world are two limiting factors in the crop production. This study was conducted to evaluate the effect of readily available agricultural residues on changing some chemical properties of saline-sodic soils. Wheat, potato, sunflower, and canola residues were separately added into three saline-sodic soils at a rate of 2% by weight and thoroughly mixed with soils. Control and treated soils were incubated for 168 days at a constant moisture and temperature. The pH, electrical conductivity (EC), soluble cations, available nitrate (NO3-) and phosphorous (P), cation exchange capacity (CEC), and exchangeable sodium percentage (ESP) were measured during the incubation. The EC increased in the response to the incorporation of plant residues, whereas the pH was reduced. The application of organic components in soils increased CEC and decreased ESP. The results showed that the maximum reduction in ESP was observed in the potato treatment because of the highest Ca2+ concentration. The average reduction in ESP of treated soil samples at the end of incubation followed this order: 16.1% (potato residue-treated soil) >12.7% (canola residue-treated soil) >11.1% (wheat residue-treated soil) >9.6% (sunflwer residue-treated soil). The potato residue was the most effective amendment in changing the chemical properties of saline-sodic soils in comparison with other organic residues. The results indicated that the application of organic residues had a positive impact on reducing the soil sodicity and improving the soil fertility depending on their chemical composition.</p>

Feasibility of coal combustion fly ash alone and in combination with gypsum and green manure for reclamation of degraded sodic soils of the Indo‐Gangetic Plains: A mechanism evaluation

AbstractThe disposal of coal combustion fly ash (FA) generated from thermal power plants is a worldwide problem. However, its low bulk density and presence of calcium and iron–aluminium sesquioxide make it a prospective ameliorant alternative to gypsum for amending degraded sodic soils. A field experiment consisting of eight treatments with variable doses of FA and gypsum along with green manure (GM) was conducted for evaluating the amelioration mechanism by measuring changes in pH, exchangeable sodium percentage, zeta (ζ) potential, and properties of meso‐aggregates (0.5–2.0 mm). The results showed that compared with control, FA significantly reduced ζ‐potential, bulk density, and pH. The GM with FA further decreased ζ‐potential and increased hydraulic conductivity. The hydrolysis of iron and aluminium sesquioxide, present in FA, functioned to lower soil pH, whereas the reduction in exchangeable sodium percentage is attributed to bioavailable Ca (27.4%). A lower FA application rate produced better crop yields. FA 2.5% (w/w) alone, compared to the FA 5% (w/w), resulted in higher yield of rice (1.96 tonnes ha−1), whereas 25% gypsum requirement (25GR) + FA 2.5% (w/w) and 25GR + FA 2.5% (w/w) + GM provided wheat yield on par with 50% gypsum requirement (50GR). The study identifies that where gypsum is scarce, the recommended amendment is 25GR + FA 2.5% or 25GR + FA 2.5% + GM when applied for sodic soil to achieve a similar yield response to standard 50GR. If gypsum is unavailable, a one‐time application of FA 2.5% (w/w) alone will improve the productivity of degraded sodic soils corresponding to more exchangeable calcium and organic carbon, which were found to be higher for meso‐aggregates (0.5–2.0 mm).

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.

The effect of chemical and organic amendments on sodium exchange equilibria in a calcareous sodic soil.

In this study, the reclamation of a calcareous sodic soil with the exchangeable sodium percentage (ESP) value of 26.6% was investigated using the cheap and readily available chemical and organic materials including natural bentonite and zeolite saturated with calcium (Ca2+), waste calcite, three metal oxide nanoparticles functionalized with an acidic extract of potato residues, and potato residues. Chemical amendments were added to the soil at a rate of 2%, while potato residues were applied at the rates of 2 and 4% by weight. The ESP in the amended soils was reduced in the range of 0.9-4.9% compared to the control soil, and the smallest and the largest decline was respectively observed in treatments containing waste calcite and 4% of potato residues. Despite the reduction in ESP, the values of this parameter were not below 15% at the end of a 40-day incubation period. So, the effect of solutions of varying sodium adsorption ratio (SAR) values of 0, 5, 10, 20, 30, 40, and 50 on sodium (Na+) exchange equilibria was evaluated in batch systems. The empirical models (simple linear, Temkin, and Dubinin-Radushkevich) fitted well to experimental data. The relations of quantity to intensity (Q/I) revealed that the potential buffering capacity for Na+ (PBCNa) varied from 0.275 to 0.337 ((cmolc kg(-1)) (mmol L(-1))(-1/2)) in the control soil and amended soils. The relationship between exchangeable sodium ratio (ESR) and SAR was individually determined for the control soil and amended soils. The values of Gapon selectivity coefficient (KG) of Na+ differed from the value suggested by U.S. Salinity Laboratory (USSL). The PHREEQC, a geochemical computer program, was applied to simulate Na+ exchange isotherms by using the mechanistic cation exchange model (CEM) along with Gaines-Thomas selectivity coefficients. The simulation results indicated that Na+ exchange isotherms and Q/I and ESR-SAR relations were influenced by the type of counter anions. The values of K G increased in the presence of bicarbonate, sulfate, and phosphate in comparison with the presence of chloride, and the largest value was obtained in the presence of phosphate. So, it can be concluded that the presence of chloride anion is more favorable to reduce ESP compared to other anions, while the presence of phosphate anion makes the reclamation process more difficult. Furthermore, it is possible to reclaim sodic soils using inexpensive and readily available compounds such as potato residues and water management.

Effect of Distillery Effluent (Spent Wash) Application on Aggregate Size Distribution and Stability in Sodic Soils

Sodic soils of sandy loam, silt loam and clay loam textures having exchangeable sodium percentage (ESP) classes of 20, 40, 60 and 80 were reclaimed with 0, 10, 20, 30 and 40 % solutions of distillery effluent (DE) and gypsum in columns. Soil texture, types of amendment and initial ESP had a larger impact on chemical properties, aggregate stability and size distribution. With increase in concentration of DE, a significant reduction in ESP, pH and insignificant increase in electrical conductivity (EC) of soil was observed for all three textures. Organic carbon (OC) content was also increased significantly in soils amended with DE. Size distribution of water-stable aggregates (WSA) of soils reclaimed using 40 % solution of DE and gypsum were found at par. Depending upon initial ESP and type of amendments used, mean weight diameter (MWD) of WSA varied from 0.51 to 1.14, 0.61 to 1.37 and 0.54 to 1.63 mm for sandy loam, silt loam and clay loam soils respectively. The percentage of water-stable macro-aggregates (WSMA) (>2 mm diameter) ranged from 2.2 to 18.2 in sandy loam, from 2.2 to 19.5 in silt loam and from 4.6 to 28.5 in clay loam soils. Combined as well as individual effects of initial ESP, EC, pH, and OC were found highly significant on WSMA and MWD of WSA in distillery effluent amended soils.

Evaluation of distillery effluent application effect on physico-chemical properties and exchangeable sodium content of sodic soils

Effect of distillery effluent (DE) application on electrical conductivity (EC), pH, organic carbon (OC), exchangeable Na, Ca, Mg, K content and exchangeable sodium percentage (ESP) of sodic soils of sandy loam (Hyperthermic family of Typic Haplaquept), silt loam (Hyperthermic family of Typic Haplaquept) and clay loam (Hyperthermic family of Typic Udic Ustochrept) textures was evaluated in a laboratory experiment. Six amendments, encompassing distilled water, DE solutions of four concentrations viz. 10%, 20%, 30% and 40%, and gypsum equivalent to 100% gypsum requirement (GR) were used to reclaim soils of 20, 40, 60 and 80 ESP class. Application of DE reduced pH and exchangeable Na content and increased OC, exchangeable Ca, Mg and K content of the soils appreciably but EC marginally. Magnitude of reduction in ESP was dependent on concentration of DE solution and the highest reduction in ESP of soil was observed with the application of 40% solution of DE. Extent of reduction in ESP with application of same concentration of DE was also found to be dependent on clay content of soil. It was relatively less in clay loam soil as compared to sandy loam soil. Results of this study thus indicated that distillery effluent could effectively be used in amending sodic soils of varying textures and ESP for improving their physico-chemical properties and reducing exchangeable sodium content.

Diffusion and cation exchange during the reclamation of saline-structured soils

Undisturbed blocks of a clay subsoil were equilibrated with solutions of 0.1, 0.3 and 1 mol c l −1 of NaCl+CaCl 2 and NaCl+CaCl 2+MgCl 2, with sodium adsorption ratio (SAR) values between 8 and 12. These were then immersed in water and the cumulative release of Na + and Ca 2+ by diffusion was measured over 90 days. The composition of the solution in the soil and the amounts of exchangeable Na + and Ca 2+ were measured before and after diffusion. The reduction in salinity in the blocks caused exchange of Ca 2+ for Na +, hydrolysis of Na + and a reduction in exchangeable sodium percentage (ESP) due both to dilution and to the more rapid diffusion of Na + than Ca 2+ out of the soil. The exchange caused a reverse concentration gradient to be established for Ca 2+ so that between 15 and 100 h after immersion, Ca 2+ was diffusing back into the soil. During the leaching of heavy textured, structured, saline, sodic soil containing both mobile and immobile water, the differential rates of diffusion of Na + and Ca 2+ may contribute to the reclamation of sodicity as salt is removed.

Sodicity and Clay Type: Influence on Decomposition of Added Organic Matter

AbstractSodicity and clay type influence the decomposition of organic matter, and hence its accumulation in soil. In this study, the interaction of these two factors was examined. Two soils were prepared by mixing sand (57%) and silt (28%), separated from one soil, with clay (15%) separated from two soils. One clay type (Urrbrae) was composed mostly of illite and kaolimite, with a mean particle diameter of 1050 nm. The other (Claremont) was composed of smectite‐dominated materials, with a mean diameter of 104 nm. The prepared soils were brought to different values of exchangeable sodium percentage (ESP) by equilibration with solutions having sodium adsorption ratios (SAR) between 0 and 30. Pea (Pisum sativum L.) straw was added at 50 g kg−1 soil, and the samples were incubated moist. After 67 d, cumulative mineralization of C was 16% greater in the soils with Urrbrae clay than in those with Claremont clay. Sodicity had a slight negative effect on mineralization, but its interaction with clay type was not significant. Differences in the mineralization of C with time and between treatments were reflected in the chemical nature of the remaining C, as determined by 13C nuclear magnetic resonance (NMR) spectroscopy. The greater the loss of C, the lower the proportion of O‐alkyl C relative to other types of C. An implication of the findings is that, following a large addition of organic matter to a sodic soil, retention of organic C would not be improved by a prior reduction in ESP, irrespective of clay mineralogy.

Effects of zero tillage and stubble retention on some properties of a cracking clay

Soil chemical and physical properties of a black cracking clay were measured after five years under a zero tillage and stubble retention trial. Stubble retention slightly increased the organic carbon content of the 0-10 cm layer, and the dispersion ratio of the 0-4 cm layer. Stubble retention increased dry aggregate size in the 0-4 cm layer of the zero tilled treatments, apparently due to a reduction in the rate of drying of the surface after rain. Changes in the distribution of cations in the surface soil developed in the absence of tillage, with lower exchangeable sodium percentage (ESP) and higher exchangeable potassium percentage in the 0-4 cm layer under zero tillage. The reduction in ESP in the 0-4 cm layer under zero tillage also reduced dispersion ratios. The ratio CEC : % clay for the 0-4 cm layer was reduced by zero tillage. Chloride profiles gave evidence for increased deep infiltration under zero tillage. This is attributed to the presence of cracks that were not closed by tillage.