Increase In Exchangeable Sodium Percentage Research Articles

Impact of a WWTP effluent overland flow on the properties of a mediterranean riparian soil

In this work we aim to assess the impact of a WWTP effluent overland flow on properties and nutrient concentrations of a riparian soil, in order to explore the potential of this practice as a nature-based treatment. We set two study zones of 150 m2 on the field, one control and one that received the WWTP effluent on its surface for one month. Samples were taken before and after the effluent overland flow system, to test the impact of the effluent on soil properties through a BACI design, and after 17 months, to evaluate the recovery of the soil. Two depths were studied: 0–5 cm and 5–20 cm. The effluent overland flow triggered an increase in exchangeable sodium percentage and a decrease in nitrate concentration in both depths, and an increase in ammonium concentration in 0–5 cm depth. After 17 months, there were not found relevant differences among zones. In conclusion, this practice could be used in the purpose to reduce the nutrient concentrations of WWTP effluents. This practice could be relevant for regions where WWTP effluents are discharged in low-flow or intermittent streams, such as semi-arid regions or the Mediterranean region.

The assessment of soil and land degradation in Volgograd region, the case of agricultural farm Donskoe

This study is aimed at assessing soil and land degradation of agricultural farmlands of Kalachev district, Volgograd region. To identify the level of land degradation, soil properties of samples taken in summer 2019 in that area were compared with average values for the same area obtained by YUZHGIPROZEM in 1982 [1]. The calculations to evaluate land degradation were based on “Methodology for determine the extent of damage of soil and land degradation” [2]. The conducted chemical and physical analysis of sampled soils demonstrated the highest level of land degradation in that area. The soils were proven to have an increase in exchangeable sodium percentage (ESP); 52% of the agricultural lands of Donskoe demonstrated these values. The assessment of the other land degradation parameters such as density, mobile phosphorus, exchange potassium, heavy metals concentration and arsenic content, toxic salts and pH (H2O) revealed lower level of degradation and insignificant occurrence in the farmland territory.

Soil salinity and land use-land cover interactions with soil carbon in a salt-affected irrigation canal command of Indo-Gangetic plain

Soil salinity poses a threat to the sustainable management of agricultural landscapes and has an effect on soil carbon storage. This study investigated land use-land cover (LULC) relations with soil organic carbon (C) in a salinity-infested landscape with inter-spun vegetated and non-vegetated land area. A sodicity infested command area (~100 ha) along Sharda Sahayak canal in Uttar Pradesh, India was selected for studying LULC effects on soil organic carbon (C) and soil properties to 60 cm soil depth. The area was divided in a grid of 100 m × 100 m, and soils were sampled and analyzed at 140 geo-referenced points representing five LULC classes. The LULC dominant in the representative area were barren-coverless (BC), barren-grass cover (BG), rice-fallow (RF), rice-wheat (RW), and rice-okra-mentha (ROM). Soil organic C decreased with depth, decreased with increase in soil pH, and decreased with an increase in exchangeable sodium percentage (ESP). The effects were highly significant in surface layers (0–0.3 m). Similarly with electrical conductivity (EC) too, soil organic C had a negative correlation. Soil organic C varied significantly with LULC. The soil organic C content decreased in the order: ROM > RW > RF > BG > BC. As the intensity of crop/plant cover increased, the soil salinity (ESP, pH and EC) decreased. The average soil ESP was maximum in BC (44%) followed by BG (30%), RF (15%), RW (8.5%), and ROM (7.0%). The cumulative probability trends indicated the probability of lesser ESP with increased vegetative cover/primary productivity. A strong (p < 0.001), a negative relationship was observed between soil organic C and pH in rice-based systems. Analysis of soil organic C stock with depth for the studied LULCs indicated 4–70% (grass cover to rice-wheat cropping sequence) increase in total soil organic C stock just by supporting vegetative cover on barren sodic land. The study was indicative of scope for soil C sequestration and reclamative effects in salt-affected areas of Indo-Gangetic region by adopting appropriate land use strategies, which may include the adoption of rice-based and grass-based cropping systems, to check the development of sodicity in soils.

Effects of biochar addition on chemical properties of a sandy soil from northeast Brazil

The application of biochar in soils is a well-established strategy to improve their physical and chemical properties, but the effects should be evaluated for each soil particularly. This study was conducted in a greenhouse of the Agricultural Sciences Unit (ASU) of Rio Grande do Norte Federal University (UFRN), in Macaiba, RN, Brazil, to evaluate the effect of biochar addition to sandy soil. The experiment was carried out in 10-L pots in a completely randomized design with four doses of biochar (0, 3500, 7000, and 10,500 kg ha−1) and four replications. The soil was collected from the top layer of a field adjacent to ASU and the biochar feedstock was wood from pruning cashew trees. The pots were cultivated with upland rice (Oryza sativa L.) and cowpea (Vigna unguiculata (l.) Walp.) in succession. The soil was sampled at 150 and 220 days after application of the treatments. The soil variables determined were pH, soil organic matter, contents of phosphorous (P), potassium (K), and calcium (Ca) plus magnesium (Mg), in addition to cation exchange capacity and exchangeable sodium percentage. Statistical analysis of experimental data included analysis of variance of the effect of biochar and regression analysis for variables with significant effect of those doses. The biochar obtained from cashew tree wood used in the experiment showed potential for use as a soil conditioner, since pH and K and P contents increased with rising doses of biochar. However, using this type of biochar can pose a risk regarding salinization, as indicated by the increase in exchangeable sodium percentage (ESP).

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

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

Characterisation of a sodic soil catena for reclamation and improvement strategies

A study to characterise the physical, chemical and morphological properties of a sodic soil on a gneissic granite catena was conducted in the Shangani Ranches. Soil profiles were sited in the main topographic zones at a distance of 135 m apart from the crest to the stream. A non-sodic profile (control) dug on the crest was also examined in order to compare properties. Results of this study and their relevance to reclamation and improvements are presented. All soils of the sodic catena exhibited a high degree of compaction, poor drainage status and restricted permeability and contained varying amounts of calcium carbonates (0.1–6.1%). A marked increase in clay content was noted in profiles of the mid to upper catena compared to those in lower catenal positions. Soil pH ranged between 7.5 and 10.1. Phenomenal increase in exchangeable sodium percentage (ESP) ranging from 36.9 to 98.9 was recorded in the subsoil horizons of the profiles in upper catenal positions. There was a slight drop in ESP values in soils of the lower catena. Final infiltration rates of 0.01 cm/min were recorded in representative sodic profiles compared to 0.33 cm/min in the control profile. Electrical conductivity values of all soils of the catena were less than 4.0 dS m −1. Bulk densities of the sodic soils were generally high (>1600 kg m −3).

Effects of sodium-contaminated wastewater on soil permeability of two New Zealand soils

There is increasing anecdotal evidence from some land treatment sites in New Zealand that irrigating sodium-contaminated wastewaters onto soils may be causing soil structural problems and reduced permeability. In this study, the effect of irrigating such waste (derived from agricultural industries) on soil physical and chemical properties was investigated in an Allophanic Soil (Te Puninga silt loam) and a Gley Soil (Waitoa silt loam). Wastewater irrigation at the sites investigated had taken place for the previous 5 years, with sodium adsorption ratios (SAR) of the wastewater varying between 17 and 51 (mmol/L)0.5 . Increases in exchangeable sodium percentage (ESP) were recorded to 300 mm depth in both soils. At the soil surface (0–20 mm), ESP had increased to 31%, compared with 0.4% at control sites. In laboratory studies using soil from the 0–20 mm layer in non-irrigated sites, leaching distilled water through repacked columns of the soil pretreated with various SAR solutions caused saturated hydraulic conductivity (K sat) to decrease below 100% at SAR greater than 3.5 and 8.5 for the Waitoa silt loam and Te Puninga silt loam, respectively. The decreases in K sat coincided with an increase in dissolved organic carbon (DOC) in collected leachate samples, and no dispersed clay was observed in the leachate. The laboratory studies would predict that effects of past irrigation of industrial wastewater at the study site would be measurable in the field due to the large ESPs that were recorded. Saturated and unsaturated hydraulic conductivity measurements carried out at irrigated sites in the field showed no evidence of reduced conductivity in the surface soil until a pressure head of –120 mm was applied, the decrease being greater for the Te Puninga soil than the Waitoa. These results, along with the laboratory studies, suggest that whereas there may have been some structural deterioration in the soil matrix as a result of irrigation with the wastewater, macropore flow at higher moisture contents in the field was sufficient to overcome any adverse effects. It is suggested that laboratory studies using repacked soil may have limited use in predicting effects of Na-contaminated wastewater on soil hydraulic properties in structured soils. The results also further support suggestions that organic matter dissolution in Na-affected soils may affect soil physical properties.

Effect of Soil Sodicity on the Growth and Cation Composition of Palmarosa and Lemongrass

ABSTRACT The effects of soil sodicity on the growth, yield, and cation composition of palmarosa (Cymbopogon martinii Roxb. Wats) and lemongrass (Cymbopogon flexuosus Steud Wats) were studied in a pot experiment. The plant height, number of tillers, and herb yield of both species significantly decreased as the exchangeable sodium in soil increased. A 50 percent reduction in herb yield over control was recorded at soil exchangeable sodium levels of 52 and 37 percent, respectively, for palmarosa and lemongrass. Increases in exchangeable sodium percentages of soil enhanced the concentration of sodium and decreased that of potassium, calcium and magnesium in vegetative tissues of both plants as compared with control. Palmarosa was lower in sodium and better able to maintain the potassium to sodium and calcium to sodium ratios in vegetative tissues under sodicity stress than lemongrass. Geranyl acetate content in the oil of palmarosa increased with increases in the soil exchangeable sodium percentage.

THE RESPONSE OF LOW AND HIGH SWELLING SMECTITES TO SODIC CONDITIONS

Swelling and dispersion of clays are the primary processes responsible for the degradation of soil hydraulic properties in the presence of exchangeable Na. The relative importance of these processes was evaluated by studying the response of low and high swelling smectites to sodic conditions. Smectite from Ariake bay sediments in Japan represented the low swelling smectite, and clay from the Kamenose landslide in Japan represented the high swelling smectite. Changes in hydraulic conductivity (HC) and clay dispersivity of sediment-sand mixtures (10, 20, and 30 g of sediment mixed with 90, 80, and 70 g of sand, respectively) as a function of total electrolyte concentration (TEC) (0.05 and 0.01 M Cl− and distilled water, (DW)) and sodium adsorption ratio ((SAR) of 0, 10, and 20) of the percolating solutions were measured. In the low swelling smectite, no changes in HC were measured in the electrolyte solutions (TEC ≥ 0.01 M Cl−) at the three SAR values. When the low swelling smectites were leached with DW, the HC of the Ca-smectite increased, whereas the HC of the SAR 10 and 20 treatments decreased. Clay dispersion and migration out of the 10% soil column was substantial. The increase in HC in Ca-mixture of low swelling smectite leached with dilute solutions was attributable to the collapse of the open microstructure that prevails in electrolyte solutions. In low swelling smectite, clay dispersion was the main process responsible for HC deterioration under sodic conditions, and smectite dispersion was prevented when TEC exceeded the flocculation value of the clay. Clay dispersion increased with an increase in exchangeable sodium percentage (ESP), and it affected the HC of the porous media only when the pores were fine and the dispersed clay plugged the conducting pores. In the high swelling smectite mixtures, a gradual decrease in the HC was measured as the TEC decreased and the SAR increased. In these mixtures, swelling was the main process responsible for HC deterioration in electrolyte solutions with TEC ≥ 0.01 M Cl−. Swelling increased with an increase in clay percentage, ESP, and decreasing TEC.

The effect of clay addition and gypsum application on the physical properties of a hardsetting red-brown earth, and the response of irrigated cotton

The growth of furrow-irrigated cotton on red-brown earths (Alfisols) of the lower Macquarie Valley in New South Wales (Australia) is often restricted by slow water penetration and poor seedling emergence, associated with structural instability and hardsetting of the soil surface. However, local landholders have overcome the problem to some extent by increasing clay content at the soil surface by using deep mouldboard ploughing (to 0.45 m) and subsequent gypsum applications. A study was carried out to determine how mouldboarding had changed the physical condition of a red-brown earth near Narromine, why the water relations had been improved, and why the effect of this operation does not appear to be permanent. Cotton growth was measured at two sites, one ploughed and treated with gypsum (PG) and the other without these treatments (C). Both sites were also deep ripped just before planting. Field studies were complemented with laboratory experiments in an attempt to separate the effects of texture modification and gypsum application. The hydraulic conductivities of surface soil and a surface-subsoil mix, each with and without gypsum, were measured. The time for columns of these soils 0.05 and 0.2 m in height to wet to the surface, and their degree of expansion or slumping on wetting, were also determined. Cotton growth was over 100% greater where the PG treatment had been applied. This improvement was associated with greater, and more uniform, water penetration into the furrows and ridges. Despite a reduction in organic matter content and exchangeable Ca: Mg ratio, and an increase in exchangeable sodium percentage, soil from the PG site had a lower dispersion index and strength, and higher hydraulic conductivity and electrical conductivity near the surface. It also had more clay in the surface, and a higher content of smectite. The hydraulic conductivity experiment suggested that gypsum may have a similar beneficial effect on both sites. In contrast, the rate of wetting experiment, which gave a better simulation of soil physical processes in the field, showed that even with gypsum the C treatment could not maintain a favourable structure. The need for further experimentation is discussed.

Effect of electrolyte solution on saturated hydraulic conductivity of soils varying in clay type and content, and iron oxides

AbstractChanges of hydraulic conductivity (HC) at electrolyte solutions having different combinations of sodium adsorption ratio (SAR)1 and electrolyte concentration (EC), were monitored in soil columns packed with samples from Rhodustalf, Chromustert, Andic Eutropept and Oxic Rhodustult, four subtropical soils varying in clay type and content, and iron oxides. In general, it was observed that the HC dropped with the decrease of EC and with the increase in SAR of solutions, or, with the increase in exchangeable sodium percentage (ESP) of the soil. In montmorillonitic soils the reduction of HC had been most pronounced, while the kaolinite‐rich soils showed only an insignificant drop in HC even at the highest SAR coupled with the lowest EC. The improvement or revival of HC from its final drop was examined upon leaching the soil columns finally with the initial high concentration solution. Montmorillonitic soils showed moderate to high revival of HC, while for montmorillonite‐illite‐kaolinite mixed clayey soils and kaolinitic soils the improvement of HC was low and practically nil respectively. The percentage revival of HC from its final drop was employed as a criterion to assess the major cause of HC reduction and it was found that irrespective of clay mineralogy “dispersion and subsequent pore plugging” played a major role in reducing the HC of soils, though in montmorillonitic soils swelling had been found to be an almost equivalent additional cause of HC drop. Simple correlations (r) between the saturated HC at varying SAR &amp; EC and different physico‐chemical and mineralogical properties have been calculated and its role and implications have been discussed.