Effect Of Sodium Adsorption Ratio Research Articles

Effects of sodium adsorption ratio and electrolyte concentration on soil saturated hydraulic conductivity

Sodium adsorption ratio (SAR) and electrolyte concentration (EC) can significantly affect water movement in soil. However, the theoretical mechanisms behind it are rarely studied. In the present study, an analytical function between electrostatic repulsive pressure (PEDL) and SAR/EC was derived in Na-Ca mixed electrolyte solutions or soil water. Soil water SAR and EC controls PEDL through surface potential and midpoint potential between two adjacent soil particles, which consequently influences the saturated soil hydraulic conductivity (Ks). Theoretical calculations show that the PEDL decreases with increasing EC and increases with increasing SAR, and the reduction in Ks is correlated with the repulsive PEDL. Five soils of different dominant clay minerals, specifically kaolinite (K), illite (I) and montmorillonite (M), were used to investigate the relationship between PEDL and change of Ks. The soils were packed in columns and leached with a serial of solutions (constant EC values of 0.5, 1, and 2 ds m−1, respectively) with increasing SAR from 0 to infinity. Our study showed that the Ks decreases with increasing PEDL. At the inflection point of the percent of Ks reduction (Kred) vs. PEDL curve, the critical PEDL values are 8.358 ∼ 8.569 atm and Kred > 92% for the Mungana soil (M), Yarrandoo soil (M, K) and Dunholm soil (M), while the average critical PEDL value is about 12.34 atm and Kred is only ∼51.75% for the Urrbrae soil (I) and Timberlea soil (K). For a given soil, the PEDL is the determinant factor, while other factors such as soil texture and clay type can also affect Ks.

Effect of sodium adsorption ratio and electric conductivity of the applied water on infiltration in a sandy-loam soil

Infiltration measurements using a double-ring infiltrometer were conducted on a sandy-loam soil located in Saudi Arabia. The measurements were performed for an undisturbed soil. The effect of sodium adsorption ratio (SAR) and electric conductivity (EC) of the applied water on infiltration rate was examined. The infiltration rate at the initial time was high, in the order 305 > 240 > 137 > 104 > 65 mm/h for SAR of 3.34, 3.52, 4.14, 4.18, and 7.60, respectively. The results showed that 180 min after the initial time of measurement in the sandy-loam soil, the final infiltration rates were in the range of 21.1–44.0 mm/h for the different qualities of water considered in this study, with an average value of 33.8 mm/h. Hence, the infiltration rate is sensitive to the SAR of the applied water. The final infiltration rate (IRf) and the final cumulative infiltration depth (Zf) after 180 min could be predicted using the following equations:IRf (mm/h) = 49.399 + 6.691 × EC (dS/m) – 6.740 × SAR (—) R2 = 0.939Zf (mm) = 148.198 + 20.074 × EC (dS/m) – 20.221 × SAR (—) R2 = 0.9387

Effect of Sodium and Magnesium on Kinetics of Phosphorus Release in Some Calcareous Soils of Western Iran

Knowledge of the rate of release of phosphorus (P) from soils resulting from poor water quality application is essential for long-term planning of crop production while minimizing the impact on groundwater quality. In this study, we examined the effect of sodium adsorption ratio (SAR) and Ca:Mg ratio of water on P release of some calcareous soils from western Iran. Nine different solutions at a total electrolyte concentration of 100 mmolc l−1 and three levels of SAR (5, 15, 45) each with Ca:Mg ratios of 1:3, 1:1, or 3:1, prepared using solutions of NaCl, CaCl2, and MgCl2, were used to extract P from the soils. The geochemical Visual MINTEQ was used to calculate saturation indices and P species at the initial and end of P release. Significantly different quantities of P were extracted by the solutions. The maximum (average of five soils) (233.6 mg kg−1) and the minimum (162.9 mg kg−1) P were extracted by an SAR 45 solution with a Ca:Mg ratio of 1:3 and SAR 15 solution with Ca:Mg ratio of 3:1, respectively. Elovich model adequately described P release. The release rate for SAR 15 with Ca:Mg of 3:1 and SAR 45 with Ca:Mg 1:3 ranges from 16.3 to 31.3 mg kg−1 h−1 and from 20.0 to 32.8 mg kg−1 h−1, respectively. In the initial stage of P release the solution samples in most soils were saturated with respect to hydroxyapatite, octacalcium phosphate, ß-tricalcium phosphate, and undersaturated with respect to dicalcium phosphate dihydrate, dicalcium phosphate, and mangnesium phosphates. At the end of P release, all solutions were saturated with respect to hydroxyapatite and under saturated with respect to other phosphate minerals. The results imply that P release from soils could be increased during use of saline and sodic irrigation water containing high Mg concentration and that P fertilization management may need modification.

Effect of sodium and magnesium on kinetics of potassium release in some calcareous soils of western Iran

The rate of potassium (K) release from soils can significantly influence their K fertility. Sodium (Na), calcium (Ca), and magnesium (Mg) in poor quality (sodic or saline) irrigation water participate in ion-exchange processes resulting in displacement and release of K from minerals into solution. This study determined the effect of sodium adsorption ratio (SAR) and Ca:Mg ratio of water on K release of some calcareous soils in western Iran. Nine different solutions at a total electrolyte concentration of 100 mmol c l − 1 and three levels of SAR (5, 15, 45) each with Ca:Mg ratios of 1:3, 1:1, or 3:1, prepared using solutions of NaCl, CaCl 2, and MgCl 2 were used to extract K from the soils. Significantly different quantities of K were extracted by the solutions. The maximum (average of five soils) (985 mg kg − 1 ) and the minimum (387 mg kg − 1 ) K were extracted by an SAR 5 solution with a Ca:Mg ratio of 1:3 and an SAR 45 solution with Ca:Mg ratio of 3:1, respectively. The importance of Mg versus Ca can be related to the specific ion effect. The kinetics of K release from soils consisted of two phases, an initial rapid phase followed by a slow phase of K release from soils. The two phases of K release are characteristic of a diffusion-controlled process. Based on the correlation coefficients, power function, parabolic diffusion, and Elovich equations adequately described K + release, whereas a first order equation did not. The K release rate for the soils was estimated by parabolic equation from the above solutions. The constant b (mg kg − 1 min − 1/2 ) in the parabolic equation was defined as the release rate and for the Ca:Mg ratio of 1:3 was 96.5 , 55.9, and 35.1.for the SARs of 5, 15, and 45, respectively. The results imply that K extraction from soils could be increased during use of saline irrigation water containing high Mg concentration. The additional K released may be more readily available to plant roots but could also be leached down below the root zone. The results suggest that long-term use of saline irrigation water with a high Mg content could lead to enough leaching of K from soil under saline and sodic conditions that K fertilization management may need modification.

Effects of poor quality irrigation waters on the nutrient leaching and groundwater quality from sandy soil

Sodium (Na+) in poor quality irrigation water participate in ion-exchange processes results in the displacement of base cations into solution and a raised concentration in groundwater. Knowledge of the rate of decrease of nutrients from soils resulting from poor water quality application is essential for long-term planning of crop production while minimizing the impact on groundwater quality. In this study, we examined the effect of sodium adsorption ratio (SAR) of irrigation water on nutrients leaching and groundwater quality in columns of sandy soil. Three types of irrigation waters at three NaCl–CaCl2 solutions with the following levels of SAR (5, 15, and 30) were synthesized in laboratory. With the application of solutions, exchange occurred between solution Na+ and exchangeable cations (Ca2+, Mg2+, and K+), resulting in the displacement of these cations and anions into solution. Increasing the level of SAR from 5 to 15 and 30 resulted in increase in the average exchangeable sodium percentage (ESP) of the soil from 10.4 to 20.3, and 32.5, respectively. Adverse effect of high Na+ concentration in the solutions on raising ESP was less pronounced in solution having low SAR. Leaching of Ca2+, Mg2+, K+, and P from soil with the application of solutions represents a significant loss of valuable nutrients. This sandy soil showed the high risk for nutrients transfer into groundwater in concentrations exceeding the groundwater quality standard. Irrigation with poor quality water, which is generally more sodic and saline than regional groundwater, increases the rate of sodification and salinization of shallow groundwater.

EFFECT OF IONIC STRENGTH AND SODIUM ADSORPTION RATIO ON THE FLOCCULATION/DISPERSION OF TWO SURFACE SOILS FROM EASTERN ARKANSAS

Poor tilth and, often, a surface crust characterize eastern Arkansas soils. Such soils have very low water infiltration and high water runoff rate leading to increase turbidity in rivers and soil erosion. Sharkey clay and Desha silt loam soils from Delta region of eastern Arkansas were used to find the effect of sodium adsorption ratio (SAR) and ionic strength (IS) on the dispersion/flocculation behaviors of the soils. Percent light transmissions at a wavelength of 530 nm were related to the concentration of clay in suspension. Each soil was equilibrated with a series of solutions having different IS and containing Na + and Ca 2+ in various proportions. At different IS and SAR, the two soils exhibited different behaviors. Clay dispersibility was a more sensitive function of SAR at low IS than at high IS.

Effect of sodium adsorption ratio and electrolyte concentrations on the saturated hydraulic conductivity of clay–sand mixtures

SummaryWe did flow experiments under saturated conditions on homoionic (Na+) kaolin–sand and illite–sand systems, containing 5, 10, and 15% clay, to validate a drainage model, and evaluate the effect of the different chemical composition of the percolating solutions on the hydraulic properties of the systems. Column drainage experiments, under a constant hydraulic head, were carried out using solutions with two sodium adsorption ratios (SAR 0 and ∞) and three electrolyte concentrations (10−2, 10−3, and 10−4 m). We calculated the saturated hydraulic conductivity, Ksat, of the systems using Darcy's law when these showed linear relationships between effluent volume and time. The drainage model was applied to characterize the flow of non‐steady‐state drainage of solutions through the porous systems. This model describes and characterizes quantitatively the drainage of solutions from soil columns that vary in intrinsic permeability, k, because of structural modifications that occur within the solid matrix of the systems. For both the systems investigated we always observed a decrease in the flow rate as electrolyte concentration decreased, or clay percentage increased. Under the same conditions the flow was faster for the kaolin system than the illite system, even though kaolin dispersed more than illite. Non‐linear relations were also observed at the smallest electrolyte concentration (10−4 m). In all cases, the equations proposed correlated well with the experimental data, confirming the soundness of the model. The flow rates observed in the experiments at SAR ∞ were unexpectedly greater than those observed at SAR 0, for the two systems, when leaching with solutions at 10−3 and 10−4 m. The values of pH and electrical conductivity of the eluates support the idea that the clay hydrolysis occurred during the saturation and, to a lesser extent, during the leaching phase of the flow.

Structural stability of Chernozemic soils as affected by exchangeable sodium and electrolyte concentration

The stability of soil structure in the presence of exchangeable Na is an important factor determining the success of irrigation developments using sodic waters. Our objective was to determine the effects of sodium adsorption ratio [SAR = Na/((Ca + Mg)/2)0.5, where concentrations are expressed in mmolc L−1] and electrolyte concentration on saturated hydraulic conductivity (K) and on macroscopic swelling in a range of Brown Chernozemic soils from southern Saskatchewan. All soils showed the same general response to sodicity (SAR) and electrolyte concentration of the leaching solution, i.e., K decreased as SAR increased and as salt concentration decreased. However, major differences existed between the soils in their susceptibility to Na-induced structural deterioration. For example, at SAR 20, the electrolyte concentration needed to maintain stable structure ranged from about 5 to 30 mmolc L−1. Our results indicated that use of a generalized threshold concentration curve to partition stable from unstable structure would not be satisfactory for all irrigated prairie soils. Texture was a major source of variation between soils; the limits on acceptable irrigation water SAR should generally be decreased as clay content increases. Swelling and dispersion of soil clays both contributed to sodicity-induced K decline. Soil clays swelled appreciably when soil exchangeable Na percentage exceeded about 10. In contrast to swelling, which was relatively insensitive to electrolyte concentration, clay dispersion was only observed at low salt concentrations (≤ 20 mmolc L−1. In implementing irrigation water:soil compatibility guidelines, it will be necessary to identify soils which deviate substantially from general or average behavior because of their propensity to disperse or swell. Key words: Sodicity hazard, threshold concentration curves, clay swelling