Levels Of Sodium Adsorption Ratio Research Articles

Cyclic Use of Sodic and Non-Sodic Canal Waters for Irrigation in Cotton-Wheat Cropping System in a Semi-Arid Region

ABSTRACT A 6-year field study (1996 to 2002) was conducted on a sandy loam soil to investigate the effect of different irrigation cycles involving sodic water (SW) and good-quality canal water (CW) on soil properties and crop yields in a cotton-wheat rotation. The treatments were: irrigation with CW, irrigation with SW (residual sodium carbonate 10 mmolc L−1) and different combinations of CW and SW applied in a cyclic mode starting with CW or SW. Irrigation with SW increased soil pH, sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP) and bulk density (BD), and decreased final infiltration rate (FIR). From the third year onward, wheat and seed-cotton yields in the SW treatment declined by 5.9% and 16.5% yr−1, respectively. Compared with SW alone, alternating irrigation between CW and SW helped maintain significantly lower pH, SAR, and ESP levels, improve FIR and BD of the soil, and achieve higher crop yields. Exchangeable sodium percentage of the soil (0 to 0.30 m layer) measured 6 years after initiation of the experiment explained 94% and 83% variation in wheat and seed-cotton yields, respectively. Compared with SW, significantly higher wheat and seed-cotton yields were obtained in irrigation cycles starting with CW involving one SW (2CW:SW, CW:SW) or SW followed by two CW irrigations (SW:2CW). Decline in seed-cotton yield was relatively greater (18% to 23%) than that in wheat (9% to 10%) in irrigation cycles starting with SW (SW:CW, 2SW:CW) and involving only one CW.

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.

Groundwater Quality Evaluation for Productive Uses— The Afram Plains Area, Ghana

Groundwater is the most widely used water resource in the Afram Plains area, Ghana. The objective of this study was to determine the distribution of fluoride, sodium adsorption ratio (SAR), and salinity (EC) in groundwater from the different aquifers in the Afram Plains area. The distribution of these parameters would enable a determination of the quality of groundwater from the different aquifer units for use in households and irrigation purposes. The inverse distance weighting, interpolator with a power of 2 was applied to 143 data points of each parameter to generate prediction maps for fluoride, SAR, and EC in the area. The distribution maps from this study show that the shale aquifers that underlie the southwestern sections of the area have the highest levels of fluoride, SAR, and EC. A narrow strip of the shale aquifer in the southwestern region produces groundwater whose fluoride level (2.2mg∕L) is higher than the World Health Organization minimum allowable fluoride concentration of 1.5mg∕L in drinking water. The feldsparthic sandstone, arkose, siltstone, and mudstone aquifers in the northeastern sections of the area produce groundwater with fluoride concentration in the range of 0.0–0.3mg∕L, which fall outside the minimum range of 0.7–1.2mg∕L required in drinking water for normal bone and dental health. The highest SAR and EC are also associated with the shale aquifers to the southwestern section of the area. Using the World Food and Agriculture Organization’s guidelines for irrigation water quality, it was determined that groundwater from the Afram Plains area will generally have a mild to moderate effect on the hydraulic properties of soils when used as irrigation water.

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.

English

Relationships between electrical conductivity (EC) and sodium adsorption ratio (SAR) changes over time in reconstructed soils at surface coal mining operations are insufficiently documented in the literature. Some minesoils (i.e., rootzone material) are classified as saline, sodic, or saline-sodic and have been considered unsuitable rooting media for establishment of native vegetation. Weatherable minerals (e.g., pyrite, calcite, gypsum, and other geologic substrates) commonly present in minesoils can mitigate the effects of elevated SAR levels by maintaining or increasing electrolytes in the soil and provide sources of exchangeable calcium and magnesium. Coversoil (i.e., topsoil) enhances this mitigation through physical and chemical buffering of minesoils. Weathering characteristics of minesoils and rooting patterns of key reclamation species were evaluated at sites from three surface coal mines in northwestern New Mexico and northeastern Arizona. Unweathered minesoils were grouped into 11 classifications based on EC and SAR. Comparison of saturated paste extracts from unweathered and weathered (6 to 14 years after reclamation) minesoils show significant (p < 0.05) reductions in SAR levels and increased EC. Weathering increased the apparent stability of saline and sodic minesoils thereby reducing risks of aggregate slaking and clay particle dispersion. Root density of fourwing saltbush (Atriplex canescens), alkali sacaton (Sporobolus airoides), and Russian wildrye (Psathyrostachys junceus) were generally unaffected by increasing minesoil EC and SAR levels. Saline and sodic minesoils can be successfully reclaimed when covered with topsoil and seeded with salt tolerant plant species.

Influence of Variable Topsoil Replacement Depths on Soil Chemical Parameters within a Coal Mine in Northeastern Wyoming, USA

Uniform topsoil replacement depths on coal mine reclaimed areas have been mandated by USA federal and state regulations; however, soils of the premine landscape are not naturally uniform in depth and vary in physical, chemical, and biological characteristics. In addition, uniform topsoil depths may actually hinder the development of diverse reclaimed plant communities. We studied the effect of varying topsoil replacement depth treatments (15, 30, and 56 cm) on soil and backfill pH, electrolytic conductivity (EC), and sodium adsorption ratio (SAR) within a reclaim-ed coal mine study area. Backfill material (also known as spoil) at this site did not possess levels of pH, EC, and SAR that were detrimental to plant growth. There was only a slight reduction in pH, EC, and SAR within the upper 15 cm depth in the reclaimed topsoil treatments with a general increase of EC and SAR in the lower portion of the replaced soil profile. Some downward movement of soluble salts within the reclaimed treatments was evident despite low precipitation. For examples, SAR in the 0–15 cm depth over all reclaimed treatments was lower in 2002 than 2000–2001, and the 0–30 cm portion of the reclaimed soil profile had reduced pH and EC, while the 30–60 cm portion had increased EC and SAR. It is anticipated that soil quality differences in terms of pH, EC, and SAR between topsoil depth treatments will be enhanced with time. Comparison of the reclaimed area to the native reference areas suggested numerous depth differences as a result of homogeneity of the replaced topsoil vs. undisturbed soil profiles.

English

Saline/sodic waters derived from wells associated with coalbed methane (CBM) gas production are being applied to rangelands and to lands used for production agriculture within the Powder River Basin (PRB) of Wyoming and Montana. Our study areas represent variable vegetation types, soil textures, treatment strategies and water application methods on sites impacted by up to 3 years of land application of saline/sodic CBM water. Vegetation parameters evaluated were forage quality, above ground biomass production, aerial cover, species diversity and infectivity of arbuscular mycorrhizae (AM) fungi. Soil data from six depth intervals to 120 cm were collected early summer, mid/late summer and fall during the 2003 water application season. Samples were analyzed for texture, bulk density, pH, electrical conductivity (EC), and sodium adsorption ratio (SAR). Infiltration and hydraulic conductivity rates were also measured. Waters from CBM gas wells in the PRB vary in quantity and quality, with average flows of around 30 liters per minute, salinity levels of about 2 dS/m and SAR's ranging from low (e.g., 5) to extremely high (e.g., 70) levels. Variable water application methods including center-pivot and side-roll irrigation and mister evaporation systems are utilized for land application. Common CBM water treatment strategies include: 1) varying application rates; 2) chemically treating water to adjust for SAR, salinity, pH and bicarbonate levels; and 3) chemically treating soil surfaces to minimize sodicity and salinity conditions. Potential advantages and disadvantages of various management strategies are discussed based on soil and vegetation data analyses. With about 20,000 CBM gas wells currently permitted or drilled in the PRB and estimates of at least 50,000 future new wells, proper CBM product water utilization is warranted.

Unsaturated flow of different quality irrigation waters through clay, clay loam and silt loam soils and its dependence on soil and solution parameters

The effect of total electrolyte concentration (TEC) and sodium adsorption ratio (SAR) of irrigation water on unsaturated hydraulic properties, viz. unsaturated hydraulic conductivity, wetting front advancement and soil-water diffusivity of clay (Typic Haplustert), clay loam (Vertic Haplustept) and silt loam (Lithic Haplorthent) soil was studied in a laboratory experiment. Twenty-four types of irrigation waters, encompassing four TEC levels, viz. 5, 10, 20 and 50 me l −1 and six SAR levels, viz. 2.5, 5, 10, 15, 20 and 30 m mol 1/2 l −1/2 were synthesised to equilibrate the soil samples using pure chloride salts of calcium, magnesium and sodium at Mg:Ca=1:2. Unsaturated hydraulic conductivity ( K θ ), was determined both directly (by ‘inflow–outflow’ vertical infiltration method for water potentials of −5 and −10 kPa) and indirectly (from diffusivity functions and soil-water retention curves) in two different water potential ranges. Wetting front advancement and diffusivity ( D θ ) were determined by the horizontal infiltration method. Water quality had larger impacts on the unsaturated hydraulic conductivities of the silt loam soil than on the clay and clay loam soils. The effects of TEC and SAR were both large for the silt loam soil whereas the effects of SAR were predominant for the clay and clay loam soils. At a water potential of −5 kPa (50 cm suction), the hydraulic conductivity of clay and clay loam soils was approximately 10 times smaller than at saturation under different quality waters. However, the hydraulic conductivity of silt loam soil was approximately 10 and 100 times smaller than at saturation for low SAR (up to 10 m mol 1/2 l −1/2) and high SAR (15 m mol 1/2 l −1/2 and above) waters, respectively. Influence of irrigation water quality on K θ increased with decreasing water content. SAR of water and exchangeable sodium percentage (ESP) of soils influenced K θ significantly. Besides SAR, TEC also influenced K θ of silt loam significantly. D θ increased with increase in TEC and/or decrease in SAR of water. The clay soil was found to be the most sensitive soil to unsaturated flow above SAR 15 m mol 1/2 l −1/2. At higher and lower water contents, the dependence of D θ on SAR of water and ESP of soil was found to be highly significant. However, in silt loam soil it was significantly dependent on TEC of water also.

Effects of prolonged irrigation with treated municipal effluent on runoff rate.

The use of domestic effluents for the irrigation of crops has been widespread in Israel for the past 30 years. The sodium adsorption ratio (SAR) of the standardized domestic effluents ranges between 4 and 6. According to the literature, when soils with SAR levels of 4 to 6 are exposed to direct raindrop impact they are subjected to enhanced aggregate disintegration, leading to sealing processes of the soil surface and subsequent increased runoff and soil erosion. However, these phenomena were not observed in the laboratory and field experiments of this study. On the other hand, a rapid decrease of the soil SAR to its initial values was observed, in laboratory and fieldwork, once the soil was subjected to a simulated rainstorm of distilled water (laboratory) or natural rainstorms (field plots). We can conclude that the process of SAR increase during irrigation with standardized effluent water is reversible. Further investigation in this direction can lead to recommendations regarding the necessary levels of domestic sewage water purification in correlation with soil types, climatic conditions, and hazards to tap water aquifers.

Effect of water quality on exchange phase — solution phase behavior of three soils

The effect of total electrolyte concentration (TEC) and sodium adsorption ratio (SAR) of water on ESR-SAR relationships of clay (Typic Haplustert), clay loam (Vertic Haplustept) and silt loam (Lithic Haplorthent) soils was studied in a laboratory experiment. Twenty four solutions, encompassing four TEC levels viz., 5, 10, 20, and 50 mmolc l—1 and six SAR levels viz., 2.5, 5, 10, 15, 20, and 30 mmol1/2l—1/2 were synthesized to equilibrate the soil samples using pure chloride salts of calcium, magnesium, and sodium at Mg:Ca = 1:2. SAR of equilibrium solution decreased as compared to the equilibrating solution and more so in waters of low salt concentration and high SAR. At low electrolyte concentration, high SAR values were not attained in the equilibrium solution because of addition of calcium and magnesium from the mineral dissolution and from the exchange phase. Irrespective of TEC, exchangeable sodium in all the soils increased by about 4.5 to 5-fold and irrespective of SAR, it increased by about 1.4- to 1.8-fold. A positive interaction of TEC and SAR influenced the ESP build-up and CEC played a major role in the visual disparity in sodication of these soils. At higher TEC levels, considerable increase in ESP was observed when it was corrected for anion exclusion and more so in silt loam followed by clay loam and clay soils. The values for Gapons' constant were in the range 0.0110—0.0176, 0.0142—0.0246, and 0.0189—0.0344 mmol—1/2l1/2 in clay, clay loam, and silt loam soils, respectively. Increase in TEC from 5 to 50 mmolc l—1 resulted in 5.84, 8.33, and 9.77 % decrease in Gapons' constant of clay, clay loam, and silt loam soils, respectively. The soils exhibited differential affinity for Ca2+, Mg2+ or Na+ under different quality waters. Regression coefficients of ESR-SAR relationship were lower for low TEC as compared with high TEC waters. 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 no sharp change was observed. Soluble salt concentration was doubled upon equilibration with low salt waters at all SAR levels in all the soils. However, the salt concentration remained unchanged upon equilibration with high salt waters. Considering pH 8.5 a boundary between soil salinity and sodicity, ESP values attained at TEC 5 mmolc l—1 were 7.34, 8.02, and 14.32 for clay, clay loam, and silt loam soils, respectively.

Effect of soil organic matter, electrical conductivity and sodium adsorption ratio on tensile strength of aggregates

The properties of soils affected by salinity and processes involving degradation of soil structure have been partly recognized. However, the effects of saline and sodic conditions on mechanical and physical properties of soils have been studied to a lesser extent. In this research, the effects of electrical conductivity (EC) and sodium adsorption ratio (SAR) on soils possessing various amounts of organic matter were assessed under laboratory conditions. The soils contained a uniform clay type, predominantly Illite. The major difference of the soils was their amount of organic matter content. The treatments consisted of solutions with definite EC and SAR (two levels of EC: 0.5 and 4 dS/m and three levels of SAR: 0, 5 and 15). The amount of tensile strength was dependent on organic matter, EC, and SAR in a way that with the increase of SAR, the tensile strength decreased. In similar SAR, treatments with higher EC exhibited greater tensile strength. Also, the soils with higher organic matter showed greater tensile strength. The analysis of variance showed the significant difference (at 1%) between the mean of parameters analyzed (soil type, sampling depth, EC, and SAR). The order of averages of tensile strength were: permanent pasture ( Agropyron elengatum)<intensive cultivation<permanent pasture ( Festuca arusdinaceae)<virgin soil. The differences were also significant for the SAR factor. The order of averages were: SAR=15<SAR=5<SAR=0.

A comparison of methods for gypsum requirement of brine-contaminated soils

An estimate of the gypsum requirement (GR) of soils affected by Na salts has practical value. The estimated GR can indicate both the quantity of any Ca amendment needed and the progress of site remediation. Four published methods to estimate GR use analytical results that do not directly include any Na in excess of the soil's cation exchange capacity (CEC). GR values thus obtained, for a 15-cm soil layer, are at most 20 to 50 t ha−1. We used these four methods to calculate the GR for various soils with known, differing salt contents. The values obtained were often inconsistent with the sodium adsorption ratio (SAR) and electrical conductivity (EC), parameters that indicate the severity of site-contamination. We also used an unpublished method to estimate GR from the amount of Ca required to bring each soil's SAR down to a threshold value of 7, on the basis of concentrations of soluble ions in a saturated paste filtrate. Estimates of GR made in this way often exceeded 50 t ha−1, but were consistent with SAR and EC levels at the various sites. This method may be more appropriate for estimating GR after brine spills on soils where Na is not readily leached and the quantity of Na exceeds the CEC. This situation often applies on the Canadian prairies. Estimating GR from the quantity of Ca required to replace exchangeable Na may be appropriate for sodic, free-draining soils in areas with high rainfall, or on irrigated land. Key words: Gypsum requirement, salt contamination, sodium adsorbtion ratio, electrical conductivity, formation water

Effect of sodicity and salinity on disaggregation and tensile strength of an Alfisol under different cropping systems

The influence of electrolyte concentration (EC) and sodium adsorption ratio (SAR) on the tensile strength and aggregate stability via flocculation and dispersion behaviour of an Alfisol varying in organic carbon content due to different cropping systems was assessed using a split-split plot experiment involving eight soils, three levels of EC and seven levels of SAR. Generally, at a given SAR value, mean weight diameter (MWD) increased with organic matter status of the soil in the following order: virgin ≫pasture>wheat>wheat-fallow. As MWD decreased, the amount of dispersible clay increased at a given SAR indicating that more surfaces exposed due to slaking of aggregates led to more clay dispersion. Statistical analysis of changes in tensile strength with various factors showed that an increase in organic matter decreased the magnitude of changes in strength induced by sodicity because organic matter tends to increase aggregate stability (higher MWD). While individual soils had significant relationships between the tensile strength of the aggregates and the amount of spontaneously dispersible clay, this relationship was poor when the results of all soils were pooled together. The amounts of dispersible clay from dry aggregates were higher than from wet aggregates and dispersive breakdown of the aggregates of sodic soils occured irrespective of the mode of wetting. The most important factor in determining the soil strength was the amount of clay dispersed during wet-sieving analysis followed by MWD.

Effect of Ca:Mg ratio on soil sodicity at different levels of sodium adsorption ratio and electrolyte concentration

A laboratory study on loamy soil (19.6% clay) with different quality waters varying in Ca : Mg ratio (1 : 1, 1 : 2, 1 : 4, 1 : 6, 1 : 8) at two levels each of salinity (6 and 12 dSm-1) and SAR (10 and 50) was carried out. Exchangeable sodium (ES), exchangeable sodium percentage (ESP), Na: (Ca+Mg) ratio and degree of dispersed clay in soil increased with increasing Mg concentration at both the levels of EC(iw) and SAR(iw). The percentage of dispersed clay was more with increasing Mg concentration at higher SAR(iw) with a lower level of EC(iw), while the reverse trend was observed with hydraulic conductivity of soil. The Ca : Mg ratio in the exchange complex decreased with increasing Mg concentration, EC(iw) and SAR(iw). Further Mg concentration in the exchange complex increased with Mg in water and EC(iw) and decreased with the rise in SAR(iw). The multiple correlations between different water parameters and soil characteristics, namely ESP, degree of dispersion and hydraulic conductivity, were calculated and regression equations were developed. The relative contributions of water parameters to ESP, degree of dispersion and hydraulic conductivity of soil were in the order SAR(iw) &gt; EC(iw) &gt; Ca : Mg; EC(iw) &gt; Ca : Mg &gt; SAR(iw), EC(iw) &gt; SAR(iw) &gt; Ca : Mg, respectively.

Effect of Exchangeable Sodium on Soil Electrical Conductivity‐Salinity Calibrations

AbstractThis study was undertaken to ascertain if soil sodicity significantly influences soil electrical conductivity (σa) — salinity calibrations. Laboratory columns of Fallbrook (Typic Haploxeralfs) and Yolo (Typic Xerorthents) soils were adjusted to various levels of salinity and sodicity by leaching them with solutions varying in electrical conductivity (σw) and sodium adsorption ratio (SAR); then σa was measured using four‐electrode techniques. Calibrations obtained between σw and σa over the σw range 2 to 20 were compared at different levels of SAR ranging between 0 to 80 or 400. The calibrations between σw and σa were found to be insignificantly influenced by variations in SAR over the range studied. Normal variations in the exchangeable Na contents of typical saline, arid‐land soils should not cause any serious misdiagnosis of soil salinity based on measurements of bulk σa and use of σw‐σa calibrations.