Extract Electrical Conductivity Research Articles

Spatially refined salinity hazard analysis in gypsum‐affected irrigated soils

AbstractThe global extent of salt‐affected agricultural land, 20% of which is deemed gypsiferous, results in billions of dollars of annual economic loss, a serious problem deserving of attention. However, the analysis of gypsiferous saline soils, such as in the irrigated Lower Arkansas River Valley (LARV) of Colorado, can result in an inflated estimation of soil salinity when using the traditional soil saturated paste extract electrical conductivity (ECe), leading to inaccurate crop yield loss predictions and misguided decisions for remediation. Sparingly soluble gypsum (CaSO4 2H2O) in these soils dissolves more readily during laboratory preparation of saturated paste extracts because of excess soil water dilution coupled with sample disturbance. We present a pragmatic linear‐regression approach to correct for this phenomenon, calibrated using two adapted methods for correcting ECe on an individual sample basis. The novel approach used electrical conductivity of pore water samples from saline fields to evaluate the accuracy of the correction methods. The approach was applied on soil samples from two surface‐irrigated, saline fields in the LARV, which were mapped using electromagnetic induction data and analysis of covariance linear regression, calibrated for ECe and ECe corrected for excess gypsum dissoultion (ECeg). Average ECeg values are as much as 26% lower than uncorrected ECe in gypsum‐biased portions of the fields. Estimation of corn salinity hazard in these gypsum‐affected areas using ECeg in lieu of ECe in a traditional yield response function generated mean relative yield values that are higher by up to 13 percentage points. We discuss lessons learned and suggest enhancements to the techniques.

Modification of Hilhorst model for saturated extract electrical conductivity estimation of coir using frequency domain reflectometry sensors – A laboratory study

Frequency domain reflectometry (FDR) sensors can measure moisture content and electrical conductivity (EC) of growing media, thus providing information for effective water and nutrient management of crops. FDR sensors generally provide the bulk EC (σb) value, which is different from the saturated extract EC (σe) values that most growers and practical studies generally use. To properly estimate σe of media, we modified the previous Hilhorst model that calculates pore water EC (σp) from FDR sensor readings. The 16 coir samples with four moisture and four EC levels were prepared, and their changes in the dielectric constant of bulk medium (εb), σb, and medium temperature from the FDR sensors were recorded and used for analysis. As a result, the εσb=0 (εb when σb is 0) of the coir used in this experiment was 1.64, which was much lower than the εσb=0 suggested for mineral soil (4.1), indicating that the medium-specific εσb=0 should be adjusted. Although σe value estimation through the Hilhorst model with adjusted εσb=0 improved, the values were still unreliable to represent the actual σe values (root mean square error, RMSE = 2.280, R2 = 0.30). To convert the σp derived from the Hilhorst model with adjusted εσb=0 to actual σe, the regression equation was applied as σe = 0.5381 × σp + 1.6493. The adjusted Hilhorst model could provide a more reliable σe estimation (RMSE = 0.929, R2 = 0.62). These results indicate that proper adjustment of εσb=0 for the specific medium is necessary, and adjusting the equation for converting σp into σe would be helpful to properly interpret the σb to practically utilize the FDR sensors for effective water and nutrient management.

Salinity spatial patterns in Mediterranean coastal areas: The legacy of historical water infrastructures

Mediterranean coastal areas have been occupied and developed intensively for a long time facing issues related to agricultural production, urbanization, tourism, preservation of natural resources often linked to salinity. This article explores the relationship between historical land planning and water management, and current soil and water salinity to gain insights into future projections.Soil samples (1185) were collected in a coastal plain of 114 km2 in the south of France and saturated paste extract Electrical Conductivity (ECsp) was deduced from 1:5 dilution. Soil salinity exhibits a wide range of variation (from 0.54 to 113.1 mS cm−1) and spatial patterns. ECsp is significantly different among soil types, higher at depth than at the surface and influenced by the distance to ancient water infrastructures (Pettitt test). Surface water and shallow groundwater samples were collected for trace element concentrations and Oxygen (18O/16O) isotope ratio measurements. The geochemical signatures indicate a mixture between surface freshwater and seawater, reveal the presence of over-salted seawater and a stratification of salinity from the surface to the depth.Results suggest that groundwater is the source of soil salinity, and illustrate the long-term impact of old water infrastructures. Less saline soils are found near the freshwater supply channel (constructed from 15th to 18th), while more saline soils are located near drainage channels. The presence of over-salted water reflects temporal evolution of the plain over the last few centuries (initially under seawater, gradually filled in, presence of ponds and salt works that have now disappeared). The current soil salinity patches continue to be a visible reminder of this evolution. The trend towards desalinization of the plain over the last few centuries has been made possible by massive freshwater inflows, which are now under threat due to the general decrease of water resources availability.

Depth-Specific Soil Electrical Conductivity and NDVI Elucidate Salinity Effects on Crop Development in Reclaimed Marsh Soils

Agricultural management decision-making in salinization-prone environments requires efficient soil salinity monitoring methods. This is the case in the B-XII irrigation district in SW Spain, a heavy clay reclaimed marsh area where a shallow saline water table and intensively irrigated agriculture create a fragile balance between salt accumulation and leaching in the root zone, which might be disrupted by the introduction of new crops and increasing climate variability. We evaluated the potential of electromagnetic induction (EMI) tomography for field-scale soil salinity assessment in this hyper-conductive environment, using EMI and limited analytical soil data measured in 2017 and 2020 under a processing tomato–cotton–sugar beet crop rotation. Salinity effects on crop development were assessed by comparing Sentinel 2 NDVI imagery with inverted depth-specific electrical conductivity (EC). Average apparent electrical conductivity (ECa) for the 1-m depth signal was 20% smaller in 2020 than in 2017, although the spatial ECa pattern was similar for both years. Inverted depth-specific EC showed a strong correlation (R ≈ 0.90) with saturated paste extract EC (ECe), [Na+] and sodium absorption ratio (SAR), resulting in linear calibration equations with R2 ≈ 0.8 for both years and leave-one-out cross validation Nash–Sutcliffe Efficiency Coefficient, ranging from 0.57 to 0.74. Overall, the chemical parameter estimation improved with depth and soil wetness (2017), yielding 0.83 < R <0.98 at 0.9 m. The observed spatial EC distributions showed a steadily increasing inverse correlation with NDVI during the growing season, particularly for processing tomato and cotton, reaching R values of −0.71 and −0.85, respectively. These results confirm the potential of EMI tomography for mapping and monitoring soil salinity in the B-XII irrigation district, while it allows, in combination with NDVI imagery, a detailed spatial assessment of soil salinity impacts on crop development throughout the growing season. Contrary to the popular belief among farmers in the area, and despite non-saline topsoil conditions, spatial EC and subsoil salinity patterns were found to affect crop development negatively in the studied field.

The Effect of Soil Texture on the Conversion Factor of 1:5 Soil/Water Extract Electrical Conductivity (EC1:5) to Soil Saturated Paste Extract Electrical Conductivity (ECe)

The electrical conductivity of soil saturated paste extract (ECe) is used as an indicator for estimating soil salinity. This method is time consuming and laborious and therefore, easier and faster methods are usually used with different soil/water ratios, such as 1:5 (EC1:5), for estimating the ECe. Usually, the relationship between ECe and EC1:5 is described by a simple linear empirical equation. The value of the conversion factor (CF) of EC1:5 to ECe is affected by the particular characteristics of the soil, such as its texture. The objective of this study is to investigate models that allow the inclusion of soil texture in the calculation of the CF, in order to improve the prediction of the ECe. A total of 148 soil samples with different soil texture and salinity levels were selected from three regions of Greece, and ECe, EC1:5, as well as clay and sand contents were determined. The results show that the CF can be estimated from an equation which incorporates the clay and sand contents through the soil saturation percentage (SP) and can give a fairly good prediction of ECe from EC1:5 (R2 = 0.9887 and RMSE = 1.39 dSm−1).

Determination of the Estrogenic Activity of Coffee Extract Solutions Prepared from Capsule Coffee Using the BG1Luc4E2 Assay

Abstract Objectives Estrogenic chemicals (ECs) possess estrogenic activity (EA) which can have harmful effects on the reproductive system. Coffee is known to have estrogenic potency due to its natural phytoestrogens, but coffee prepared from plastic capsules (capsule coffee) may increase exposure to ECs and consequently increase EA, potentially increasing risk to reproductive health. The objective of this study was to determine the EA of capsule coffee extract solutions in vitro. Methods Six varieties of capsule coffee and two varieties of coffee prepared from whole beans using a stainless-steel French press were first brewed then concentrated and extracted. The BG1Luc4E2 assay was then conducted to determine the EA of the coffee extracts. The normalized EA (% RME2) of the coffee extracts was determined as the relative estrogenic potency compared to the maximum normalized EA of the positive control 17β-estradiol (set to 100 % RME2). EA was determined if at least one data point on the concentration-response curve was above 15% RME2 and confirmed via inhibition with the estrogen receptor antagonist ICI 182,780. The correlation between the EA estimated by the BG1Luc4E2 assay and the estrogenic potential (EEQ) was determined with Spearman's rank correlation coefficient. Results All eight coffee extract solutions tested positive for EA and results were confirmed by their complete inhibition with ICI. The level of EA for the six capsule coffee extracts ranged from 48 to 56 % RME2, while the level of EA for the two coffee varieties prepared from whole beans were 40 and 42 % RME2. There was a significant correlation between EA and EEQ was (ρ = 0.8857, P = 0.0333). Conclusions These results indicate that the EAs of capsule coffees were higher than that of coffee prepared from a plastic-free method and that the EA measured in an in vitro model was correlated with the calculated estrogenic potential of the coffee extract's EC contents. Future studies are warranted in in vivo models as well as in humans as tests of estrogenic potency in vitro do not necessarily predict the effects in living organisms. Funding Sources This study was supported by the National Institutes of Health.

Reclamation of Coastal Saline Wasteland Using Drip Irrigation and Embedded Subsurface Pipes

A 3‐yr field experiment investigated the impact of drip irrigation and embedded subsurface drain pipes on salt leaching and Chinese rose (Rosa chinensis Jacq.) growth in a severely degraded saline soil located in north China. The experiment consisted of five soil matric potential (SMP) treatments where the soil matric potential at 0.2 m below the emitter was −5, −10, −15, −20 and −25 kPa in 2014 and 2015 and then decreased to −15, −20, −25, −30 and −35 kPa in 2016. With time, the size of the low salinity zone increased and the soil extract electrical conductivity (ECe) in surface 40 cm decreased from 27.32 to <1.5 dS m−1. Soil water content increased with increasing SMP threshold values in the surface soil profile, but there were no significant differences among treatments in the deep layer. Soil pH values increased and then decreased for all treatments and obvious alkalization occurred, especially in the root zone. High survival rates of Chinese rose with values >96% were obtained in 2014 for all treatments and these decreased with time, especially in the lower SMP treatments in 2016. An SMP higher than −5 kPa in the first year, −10 kPa in the second year and −20 kPa in the third year, combined with an irrigation water event of 10 mm, can be used for rose drip‐irrigation scheduling, which can maintain survival rates of >85% on reclamation of coastal saline sandy loam soil with embedded subsurface pipes.Core Ideas Chinese roses were grown on coastal saline soils under drip irrigation and embedded subsurface pipe. Five soil matric potential thresholds were set for drip irrigation. The drip irrigation scheduling for rose grown in coastal saline soils was determined.

Response of Spring Wheat to Sulfate‐Based Salinity Stress under Greenhouse and Field Conditions

Core Ideas Spring wheat response to sulfate‐based salinity stress was evaluated under greenhouse and field conditions. Soil salinity was highly variable, both horizontally and vertically, in fields. Soil ECe affected crop growth and relative yield only under greenhouse conditions. Under field conditions, low soil ECe in the root zone resulted in greater salinity tolerance. Spring wheat (Triticum aestivum L.), a moderately salt‐tolerant crop, is often grown in saline areas worldwide. This study was conducted to assess spring wheat response to sulfate‐based salts under greenhouse and field conditions. In a greenhouse experiment, salinity treatments (control and 3.0, 5.0, 9.0, and 15.0 dS m−1) were established by adding Na2SO4 and MgSO4⋅7H2O salts in soil–silica mixes. Similarly, field studies were conducted in naturally saline farmers’ fields in eastern North Dakota for a total of four site‐years. In the fields, the soil was sampled to the 120‐cm depth, and the depth‐weighted mean root‐zone salinity was calculated. Results indicated a variable response of spring wheat to salinity under greenhouse and field conditions. Under greenhouse conditions, plant height and number of tillers per plant decreased significantly at a soil saturated paste extract electrical conductivity (ECe) of 5 dS m−1 and above. Similarly, root growth decreased significantly at a ECe of 9.0 dS m−1 and above. Relative kernel and straw yields were unaffected by sulfate salts up to 8.2 and 2.9 dS m−1, respectively. Above the threshold value, the kernel and straw yields declined by 12.0 and 4.9% per unit increase in ECe, respectively. In naturally saline fields, soil salinity decreased with soil depth, and the spring wheat responded by decreasing plant height by 1.2 cm per unit increase in ECe. However, root growth and relative crop yields were maintained. Our results suggest that the majority of the crop roots were exposed to low salinity levels in the surface soil layers in naturally saline fields, providing greater salinity tolerance in the crops.

Adjustment of Soil Saturated Paste Extract Electrical Conductivity and Sodium Adsorption Ratio for Excess Gypsum Dissolution Using Equilibrium Geochemical Modeling

Core Ideas In gypsum‐bearing soils, excess dissolution occurs in the soil saturated paste extract. EC and SAR may be adjusted for dissolution effects using geochemical modeling. Characterization of salinity and sodicity hazard is improved. Soil saturated paste extract (SPE) electrical conductivity (ECe) and sodium adsorption ratio (SARe) are widely used measures of soluble salts used to evaluate the salinity hazard to crop growth and the sodicity hazard to soil permeability. In gypsum‐bearing soils, sparingly soluble gypsum dissolves during preparation of the SPE as a result of soil water dilution. This produces a higher measured ECe and lower SARe than would be measured if only field‐soluble gypsum were present. As part of a soil remediation project, samples were collected from the location of a former oil and gas production facility with highly saline‐sodic, brine‐affected soils. The naturally calcareous silt loam soil with a smectitic clay fraction was previously amended with gypsum to mitigate elevated sodicity, of concern for sodic effects on soil permeability. The equilibrium geochemical modeling software program ExtractChem was used to model ECe and SARe in the absence of excess gypsum dissolution by first modeling EC and SAR at field water content and then modeling ECe and SARe at saturated paste water content while excluding gypsum from the modeled reaction. For samples with measured ECe <3 dS m−1, ECe modeled in the absence of excess gypsum dissolution was up to 52% lower than measured, and for samples with measured SARe <2, modeled SARe was up to 53% higher than measured. As remediation progressed, and ECe and SARe decreased toward target values, the magnitude of the excess gypsum effect was sufficient to affect the evaluation of remedial progress. Equilibrium geochemical modeling adjustment of ECe and SARe for gypsum dissolution that occurs as a result of SPE preparation is recommended to improve the evaluation of the progress of remediation of gypsum‐bearing, salt‐affected soil.

Visible-Near Infrared Reflectance Spectroscopy for Rapid Characterization of Salt-Affected Soil in the Indo-Gangetic Plains of Haryana, India

Management of salt-affected soils is a challenging task in the input intensive rice-wheat cropping zone of the Indo-Gangetic plains (IGP). Timely detection of salt-affected areas and assessment of the degree of severity are vital in order to narrow down the potential gap in yield. Conventional laboratory techniques of saturation extract electrical conductivity (ECe) and sodium adsorption ration (SAR) for soil salinity assessment are time-consuming and labour intensive; the VNIR (visible-near infrared) reflectance spectroscopy technique provides ample information on salinity and its attributes in an efficient and cost-effective way. This study aims to develop robust soil reflectance spectral models for rapid assessment of soil salinity in the salt affected areas of the IGP region of Haryana using VNIR reflectance spectroscopy. The results indicated that the spectral region between 1390 and 2400 nm was highly sensitive to measure changes in salinity. The developed hyperspectral models explained more than 80 % variability in ECe, and other salinity related attributes (saturated extract Na+, Ca2+ + Mg2+, Cl− and SAR) in the validation datasets. With the increasing availability of data from hyperspectral sensors in near future, the study will be very useful in real time monitoring of soils in the spatio-temporal context; enabling the farmers of IGP area to deal with salt degradation more effectively and efficiently.

Use of geophysical survey as a predictor of the edaphic properties variability in soils used for livestock production

The spatial variability in soils used for livestock production (i.e. Natraquoll and Natraqualf) at farm and paddock scale is usually very high. Understanding this spatial variation within a field is the first step for site-specific crop management. For this reason, we evaluated whether apparent electrical conductivity (ECa), a widely used proximal soil sensing technology, is a potential estimator of the edaphic variability in these types of soils. ECa and elevation data were collected in a paddock of 16 ha. Elevation was negatively associated with ECa. Geo-referenced soil samples were collected and analyzed for soil organic matter (OM) content, pH, the saturation extract electrical conductivity (ECext), available phosphorous (P), and anaerobically incubated Nitrogen (Nan). Relationships between soil properties and ECa were analyzed using regression analysis, principal components analysis (PCA), and stepwise regression. Principal components (PC) and the PC-stepwise were used to determine which soil properties have an important influence on ECa. In this experiment elevation was negatively associated with ECa. The data showed that pH, OM, and ECext exhibited a high correlation with ECa (R2=0.76; 0.70 and 0.65, respectively). Whereas P and Nan showed a lower correlation (R2=0.54 and 0.11 respectively). The model resulting from the PC-stepwise regression analysis explained slightly more than 69% of the total variation of the measured ECa, only retaining PC1. Therefore, ECext, pH and OM were considered key latent variables because they substantially influence the relationship between the PC1 and the ECa (loading factors>0.4). Results showed that ECa is associated with the spatial distribution of some important soil properties. Thus, ECa can be used as a support tool to implement site-specific management in soils for livestock use.

Growth and yield responses in wheat and barley to potassium supply under drought or moderately saline conditions in the south-west of Western Australia

This study assessed whether more potassium (K) was required for optimal growth and grain yield of cereal crops under drought and salinity than under non-stressed conditions. In 2011, three experiments on wheat (Triticum aestivum L.) with four K rates (0, 20, 40, 80 kg K/ha), four application times (0, 5, 10, 15 weeks after sowing, WAS) and two sources (KCl, K2SO4) were conducted in the central and southern grainbelts of Western Australia. The lack of plant response to K supply at the sites of Bolgart (36 mg K/kg at 0–30 cm) and Borden (25 mg K/kg at 0–30 cm), compared with significant gain in K uptake, dry matter and grain yield at Dowerin (29 mg K/kg at 0–30 cm), was not explained by differences in soil K levels. However, rain fell regularly through the growing season at Bolgart and Borden, whereas a dry spell occurred from stem elongation to grain development at Dowerin. The effectiveness of K application time followed the trend of 0, 5 > 10 > 15 WAS. In 2012, barley (Hordeum vulgare L.) was grown on a moderately saline (saturation extract electrical conductivity ~4 dS/m) and low K (20 mg K/kg) farm in the central grainbelt and treated with 0, 20, 40 and 120 kg K/ha. Applying K increased K uptake but decreased Na uptake, especially at 120 kg K/ha. Plant growth and grain yield increased with K supply, but the difference between the K rates was relatively small, indicating possible partial K substitution by Na. Higher than normal fertiliser K supply on low K soils would enhance the adaptation by cereals to water-limited environments, but K-fertiliser management on moderately saline soils may need to account for both K and Na uptake and use by the crops.

Soil salinization as a threat to the sustainability of deficit irrigation under present and expected climate change scenarios

Deficit irrigation (DI) strategies using moderately saline waters save water, but may enhance soil salinization. Based on data gathered during years 2007–2012 in three drip-irrigated grapevine, peach, and nectarine crops subjected to several irrigation and soil-mulching treatments, we assessed trends in root-zone soil salinity [saturation extract electrical conductivity (ECe)], related the changes in soil salinity (ΔECe) to field-wide leaching fraction (LF), evaluated management strategies for soil salinity control, and examined the sustainability of DI strategies under present and expected climate change (CC) scenarios in the Middle Ebro River Basin (ERB, Spain). ECe increased in 82 % of the irrigation seasons and decreased in 75 % of the non-irrigation seasons examined. Soil salinization trends were not apparent during the study years due to these annual salt accumulation–salt leaching cycles. ECe increases were higher in the more severe DI treatments and in the geotextile-mulched soil and lower in the full and less severe irrigation treatments and in the organic-mulched soil. As expected, ΔECe and LF were linearly and negatively correlated (P < 0.01), indicating that soil salinization increased with decreasing LF. These linear relationships provided a way to evaluate best management strategies (increased irrigation, rainfall harvesting, and soil mulching) for soil salinity control. These strategies decreased soil salinization, but did not guarantee the sustainability of severe DIs in the study area. The application of these relationships to the CC precipitation and crop evapotranspiration projections in the ERB shows that the examined DI strategies will be unsustainable due to soil salinization.

Effectiveness of inorganic and organic mulching for soil salinity and sodicity control in a grapevine orchard drip-irrigated with moderately saline waters

Soil mulching is a sensible strategy to reduce evaporation, accelerate crop development, reduce erosion and assist in weed control, but its efficiency for soil salinity control is not as well documented. The benefits of inorganic (plastic) and organic (grapevine pruning residues) mulching for soil salinity and sodicity control were quantified in a grapevine orchard (cultivars ‘Autumn’ Royal and ‘Crimson’) drip-irrigated with moderately saline waters. Soil samples were taken at the beginning and end of the 2008 and 2009 irrigation seasons in six vines of each cultivar and mulching treatment. Soil saturation extract electrical conductivity (ECe), chloride (Cle) and sodium adsorption ratio (SARe) values increased in all treatments of both grapevines along the irrigation seasons, but the increases were much lower in the mulched than in the bare soils due to reduced evaporation losses and concomitant decreases in salt evapo-concentration. The absolute salinity and sodicity daily increases in ‘Autumn’ and ‘Crimson’ 2008 and in ‘Crimson’ 2009 were on the average 44% lower in the plastic and 76% lower in the organic mulched soils than in the bare soil. The greater efficiency of the organic than the plastic mulch in ‘Crimson’ 2009 was attributed to the leaching of salts by a precipitation of 104 mm that infiltrated the organic mulch but was intercepted by the plastic mulch. Although further work is needed to substantiate these results, the conclusion is that the plastic mulch and, particularly, the organic mulch were more efficient than the bare soil for soil salinity and sodicity control.

Regulated deficit irrigation, soil salinization and soil sodification in a table grape vineyard drip-irrigated with moderately saline waters

Irrigation with moderately saline waters may provoke soil salinization and sodification. The objectives of this three-year study were (1) to quantify these processes in two seedless table grapevines (Vitis vinifera cvs. Autumn Royal and Crimson) subject to a full irrigation and two regulated deficit irrigations (RDI, irrigated at 80% and 60% of net irrigation requirements from post-veraison till harvest) with 1.7dSm−1 electrical conductivity irrigation waters, and (2) to assess the impact of soil salinization on grapevine's response. Soil samples were taken three times along each irrigation season and soil solution samples were extracted weekly by suction cups. Soil saturation extract electrical conductivity (ECe) and sodium adsorption ratio (SARe) were high in Autumn Royal (4.4dSm−1 and 6.1 (mmoll−1)0.5) and very high in Crimson (7.0dSm−1 and 8.6 (mmoll−1)0.5) due to relatively low leaching fractions (LF) (0.20 in Autumn Royal and 0.13 in Crimson). Soil solution salinity and sodicity were generally higher in the more severe RDI than in the full irrigation treatment. Soil salinity and sodicity generally increased along the irrigation seasons and decreased along the non-irrigation seasons. Salt accumulation or leaching and LF were significantly correlated, so that LF estimates could anticipate the required irrigation depths for soil salinity control. Grapevine yield declined with increases in soil salinity. Leaf Na concentrations were very low (<0.1%), but leaf Cl concentrations were higher and the maximum value of 0.61% measured in the more severe Crimson RDI treatment was within the interval reported as toxic in grapevine. Despite the water saving benefits of drip irrigation in combination with deficit irrigation strategies, its implementation in low-precipitation semiarid areas must be cautiously assessed and monitored because soil salinization and sodification may threaten the sustainability and profitability of these grapevine orchards irrigated with moderately saline waters.

Statistical relationships between soil colour and soil attributes in semiarid areas

Soil colour has become one of the most innovative indicators used to adjust amendment and fertilizer rates in precision agriculture. This paper uses a combination of colour variables together with geographical, management and pedologic variables in order to find relationships between the three colour components (lightness, hue, and chroma) and several soil characteristics, in a semiarid environment. In these areas soils are weakly developed, and organic matter, nitrogen, phosphorous and iron soil contents are usually low and undergo high spatial variability. Multivariate analysis was used to find statistical relationships that: determine soil colour in those environmental areas; reveal the most appropriate chromatic variables for each case; and determine the interactions between variables that can mask the effects of individual variables. Colour measurements were collected with a trichromatic colorimeter . Eighteen soil variables were used, of which eight resulted in statistically significant correlations with colour components. Those variables were sand (%), clay (%), parent material (marls), soil organic carbon (SOC), carbonate content , total nitrogen (TN), iron, and 1:5 soil:water extract electrical conductivity (EC 1:5 ). Only sand was significant for all three colour components. The content of organic carbon was not significant in multiple regression analysis with respect to soil lightness in this study of semiarid soils . However it was significant in bivariate regression, in the same way as found in other studies. • Carbonates, EC, texture, iron and SOC are the most significant variables. • Low levels of chromogen elements do not complicate statistical correlations. • Specific soil variables are significantly correlated with lightness, chroma and hue.

Non-destructive technique for broadband characterization of carbon nanotubes at microwave frequencies

This paper presents a broadband microwave non-destructive technique for characterization of carbon nanotubes (CNTs). Typically, commercially available carbon nanotubes are powder-like samples and, therefore, in this paper, a broadband characterization technique to extract electrical conductivity of powder materials is developed. The technique uses a microstrip line configuration in conjunction with a cavity resonator technique. The electrical conductivity of CNTs is extracted from the measured attenuation in the signal response (|S21|dB) for the microstrip configuration with a signal trace made of copper and a ground plane filled with CNT samples. A resonant cylindrical cavity is also used in the measurement process to help determine a correction factor for the surface roughness of the CNT microstrip ground plane. A novel method to take attenuation due to surface roughness into account to determine conductivity of CNTs is introduced. Experimental and numerical verification of the proposed method is provided. The method developed in this work provides a cost-effective solution where significant amount of time and cost are reduced in the sample preparation process. Measurement results for the electrical conductivity of single-walled CNTs and multi-walled CNTs are presented.

Irrigation with saline-sodic water: effects on two clay soils

The results of a 4-year experiment aimed at evaluating the effect of irrigation with saline-sodic water on the soil are reported. The research was carried out at the Campus of the Agricultural Faculty of Bari University (Italy) on 2 clay soils (Bologna – T 1 and Locorotondo – T 2 ). The soils were cropped to borlotto bean ( Phaseolus vulgaris L.), capsicum ( Capsicum annuum L.), sunflower ( Helianthus annuus L.), wheat ( Triticum durum Desf) grown in succession; the crops were irrigated with 9 saline-sodic types of water and subjected to two different leaching fractions (10% and 20% of the watering volume). The 9 solutions were obtained dissolving in de-ionised water weighted amounts of sodium chloride (NaCl) and calcium chloride (CaCl 2 ), deriving from the combination of 3 saline concentrations and 3 sodicity levels. The crops were irrigated whenever the water lost by evapotranspiration from the soil contained in the pots was equal to 30% of the soil maximum available water. The results showed that, though the soils were leached during the watering period, they showed a high salt accumulation. Consequently, the saturated soil extract electrical conductivity increased from initial values of 0.65 and 0.68 dS m -1 to 11.24 and 13.61 dS m -1 at the end of the experiment, for the soils T 1 and T 2 , respectively. The saline concentration increase in irrigation water caused in both soils a progressive increase in exchangeable sodium, and a decrease in exchangeable calcium and non-significant variations in exchangeable potassium (K) and magnesium (Mg).

Delineation of management zones with measurements of soil apparent electrical conductivity in the southeastern pampas

Peralta, N. R., Costa, J. L., Balzarini, M. and Angelini, H. 2013. Delineation of management zones with measurements of soil apparent electrical conductivity in the southeastern pampas. Can. J. Soil Sci. 93: 205–218. Site-specific management demands the identification of subfield regions with homogeneous characteristics (management zones). However, determination of subfield areas is difficult because of complex correlations and spatial variability of soil properties responsible for variations in crop yields within the field. We evaluated whether apparent electrical conductivity (ECa) is a potential estimator of soil properties, and a tool for the delimitation of homogeneous zones. ECamapping of a total of 647 ha was performed in four sites of Argentinean pampas, with two fields per site composed of several soil series. Soil properties and ECawere analyzed using principal components (PC)–stepwise regression and ANOVA. The PC–stepwise regression showed that clay, soil organic matter (SOM), cation exchange capacity (CEC) and soil gravimetric water content (θg) are key loading factors, for explaining the ECa(R2≥0.50). In contrast, silt, sand, extract electrical conductivity (ECext), pH values and [Formula: see text]-N content were not able to explain the ECa. The ANOVA showed that ECameasurements successfully delimited three homogeneous soil zones associated with spatial distribution of clay, soil moisture, CEC, SOM content and pH. These results suggest that field-scale ECamaps have the potential to design sampling zones to implement site-specific management strategies.

Accumulation and Mobility of Salts in Soil as Influenced by Primary Biomethanated Spentwash

A soil column laboratory experiment was carried out at the central campus, Mahatma Phule Agricultural University, Rahuri, India during 2008–2009 to study the accumulation and mobility of salts in Typic Haplusterts as influenced by primary biomethanated spentwash (PBSW). The PBSW was applied in three different levels (0.5, 1.0, and 2.5 cm) and then tap water with low salinity and low sodium hazard (C1S1 class) was used to carry out leaching in four different levels of water at the pore volume of soil (WPVS) (0.5, 1.0, 1.5, and 2.0). The electrical conductivity (EC) in the soil increased significantly with increasing levels of PBSW and decreased with increasing levels of WPVS in surface (0–15 cm deep) and subsurface (15–30 cm deep) soil layers. The exchangeable calcium (Ca2+), magnesium (Mg2+), and potassium (K+) increased, whereas exchangeable sodium (Na+) decreased with increasing levels of PBSW and WPVS in surface and subsurface layers of soil. The organic carbon content increased with increasing levels of PBSW and decreased with increasing levels of WPVS in both the soil layers. The cation exchange capacity (CEC) increased with increasing levels of PBSW and WPVS in both the soil layers. The exchangeable sodium percentage (ESP) decreased with increasing levels of PBSW and WPVS over the initial values of soil in both the layers. The pH of saturated paste (pHs) was reduced and electrical conductivity of extract (ECe) was increased with increasing levels of PBSW and WPVS in both the layers. The Na+ content of saturation paste extract increased significantly with increasing levels of PBSW and WPVS in both the soil layers.