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1.
Abstract

Electrical conductivity (EC) methods were tested using combinations of surrogate irrigation (SI) waters, soil salinity levels, and soils ground or retaining aggregates. The EC varied in low-salinity soils saturated with SI; the sum of the baseline ECe and SI EC were not equal to the measured EC. The baseline ECe and the SI EC sum in the high‐salinity ground soils were not equal to the any measured ECs. Salt‐removal potential from gypsiferous soils was examined using multiple extractions from the same soil sample. Calcium concentrations remained consistent over 14 extractions, whereas Na concentrations decreased. The ECe decreased from more than 8 dS m?1 in the initial extraction, to approximately 4 dS m?1 by the 9th to 14th extraction. Multiple extraction data suggest that improved leaching will not lower soil ECs to less than approximately 4 dS m?1 because of gypsum and calcite reservoirs in the tested soils.  相似文献   

2.
To understand the limitations of saline soil and determine best management practices, simple methods need to be developed to determine the salinity distribution in a soil profile and map this variation across the landscape. Using a field study in southwestern Australia, we describe a method to map this distribution in three dimensions using a DUALEM‐1 instrument and the EM4Soil inversion software. We identified suitable parameters to invert the apparent electrical conductivity (ECa – mS/m) data acquired with a DUALEM‐1, by comparing the estimates of true electrical conductivity (σ – mS/m) derived from electromagnetic conductivity images (EMCI) to values of soil electrical conductivity of a soil‐paste extract (ECe) which exhibited large ranges at 0–0.25 (32.4 dS/m), 0.25–0.50 (18.6 dS/m) and 0.50–0.75 m (17.6 dS/m). We developed EMCI using EM4Soil and the quasi‐3d (q‐3d), cumulative function (CF) forward modelling and S2 inversion algorithm with a damping factor (λ) of 0.07. Using a cross‐validation approach, where we removed one in 15 of the calibration locations and predicted ECe, the prediction was shown to have high accuracy (RMSE = 2.24 dS/m), small bias (ME = ?0.03 dS/m) and large Lin's concordance (0.94). The results were similar to those from linear regression models between ECa and ECe for each depth of interest but were slightly less accurate (2.26 dS/m). We conclude that the q‐3d inversion was more efficient and allowed for estimates of ECe to be made at any depth. The method can be applied elsewhere to map soil salinity in three dimensions.  相似文献   

3.
The aim of this study was to determine the salt tolerance of pepper (Capsicum annuum L.) under greenhouse conditions and to examine the interactive effects of salinity and nitrogen (N) fertilizer levels on yield. The present study shows the effects of optimal and suboptimal N fertilizer levels (270 kg ha?1 and 135 kg ha?1) in combination with five different irrigation waters of varying electrical conductivity (EC) (ECiw = 0.25, 1.0, 1.5, 2.0, 4.0, and 6.0 dS m?1) and three replicates per treatment. At optimal N level, yield decreased when the irrigation water salinity was above ECiw 2 dS m?1. At the suboptimal N level, a significant decrease in yield occurred only above ECiw 4 dS m?1. At high salinity levels the salinity stress was dominant with respect to yield and response was similar for both N levels. Based on the results it can also be concluded that under saline conditions (higher than threshold salinity for a given crop) there is a lesser need for N fertilization relative to the optimal levels established in the absence of other significant stresses.  相似文献   

4.
Electrical conductivity(EC) of soil-water extracts is commonly used to assess soil salinity. However, its conversion to the EC of saturated soil paste extracts(ECe), the standard measure of soil salinity, is currently required for practical applications. Although many regression models can be used to obtain ECe from the EC of soil-water extracts, the application of a site-specific model to different sites is not straightforward due to confounding soil factors such as soil texture. This study was...  相似文献   

5.
Abstract. Diagnosis of soil salinity and its spatial variability is required to establish control measures in irrigated agriculture. This article shows the usefulness of electromagnetic (EM) and soil sampling techniques to map salinity. We analysed the salinity of a 1‐ha plot of surface‐irrigated olive plantation in Aragon, NE Spain, by measuring the electrical conductivity of the saturation extract (ECe) of soil samples taken at 22 points, and by reading the Geonics EM38 sensor at 141 points in the horizontal (EMH) and vertical (EMV) dipole positions. EMH and EMV values had asymmetrical bimodal distributions, with most readings in the non‐saline range and a sharp transition to relatively high readings. Most salinity profiles were uniform (i.e. EMH=EMV), except in areas with high salinity and concurrent shallow water tables, where the profiles were inverted as shown by EMH > EMV, and by ECe being greater in shallow than in deeper layers. The regressions of ECe on EM readings predicted ECe with R2 > 84% for the 0–100 to 0–150 cm soil depths. We then produced salinity contour maps from the 141 ECe values estimated from the electromagnetic readings and the 22 measured values of ECe. Owing to the high soil sampling density, the maps were similar (i.e. mean surface‐weighted ECe values between 3.9 dS m?1 and 4.2 dS m?1), although the electromagnetically estimated ECe improved the mapping of details. Whereas soil sampling is preferred for analysing the vertical distribution of soil salinity, the electromagnetic sensor is ideal for mapping the lateral variability of soil salinity.  相似文献   

6.
For understanding the effects of soil salinity and nitrogen (N) fertilizer on the emergence rate, yield, and nitrogen-use efficiency (NUE) of sunflowers, complete block design studies were conducted in Hetao Irrigation District, China. Four levels of soil salinity (electrical conductivity [ECe] = 2.44–29.23 dS m?1) and three levels of N fertilization (90–180 kg ha?1) were applied to thirty-six microplots. Soil salinity significantly affected sunflower growth (P < 0.05). High salinity (ECe = 9.03–18.06 dS m?1) reduced emergence rate by 24.5 percent, seed yield by 31.0 percent, hundred-kernel weight by 15.2 percent, and biological yield by 27.4 percent, but it increased the harvest index by 0.9 percent relative to low salinity (ECe = 2.44–4.44 dS m?1). Application of N fertilizer alleviated some of the adverse effects of salinity, especially in highly saline soils. We suggest that moderate (135 kg ha?1) and high (180 kg ha?1) levels of N fertilization could provide the maximum benefit in low- to moderate-salinity and high- or severe-salinity fields, respectively, in Hetao Irrigation District and similar sunflower-growing areas.  相似文献   

7.
Most of the crop salt tolerance studies are often conducted in a glasshouse and are limited under field conditions. Therefore, the present research study was conducted under field conditions to evaluate the performance of six wheat cultivars at five salinity levels (EC 0, 3, 6, 9, and 12 dS m?1) in split plot design with three replications. Increasing salinity significantly increased soil pH, electrical conductivity (EC), and sodium adsorption ratio (SAR). Yield parameters of different cultivars were affected more at higher salinity levels than lower in two years. Data over two years revealed that up to EC 9 dS m?1 cultivars PBW 658 and HD 2967 performed ???better on the absolute yield basis but PBW 621 produced ?higher relative yield. At EC 12 dS m?1, PBW 658 produced significantly higher grain yield (4.23 t ha?1) than cultivars HD 2967 (4.11 t ha?1) and PBW 621 (3.99 t ha?1); therefore, should be preferred at salinity more than 9 dS m?1.  相似文献   

8.
A laboratory incubation experiment was conducted to evaluate the effect of magnesium chloride–induced salinity on carbon dioxide (CO2) evolution and nitrogen (N) mineralization in a silty loam nonsaline alkaline soil. Magnesium chloride (MgCl2) salinity was induced at 0, 4, 8, 12, 16, 20, 30, and 40.0 dS m?1 and measured CO2 evolution and N mineralization during 30 days of incubation. Both CO2 evolution and N mineralization decreased significantly with increasing salinity. The cumulative CO2 evolution decreased from 235 mg kg?1 soil at electrical conductivity (EC) 0.65 dS m?1 to 11.9 mg kg?1 soil at 40 dS m?1 during 30 days of incubation. Similarly, N mineralization decreased from 185.4 mg kg?1 at EC 0.65 dS m?1 to 34.45 mg kg?1 at EC 40.0 dS m?1 during the same period. These results suggested that increasing magnesium chloride salinity from 4 dS m?1 adversely affect microbial activity in terms of carbon dioxide evolution and N mineralization.  相似文献   

9.
Reclamation of sodic soils is proving increasingly vital as greater land area becomes salt-affected in the northern Great Plains of the United States. Flue gas desulfurization gypsum (FGDG) can be an agriculturally important resource for increasing land productivity through the amelioration of sodic soils. Biochar is also considered as an aid in reclaiming degraded soils. In this incubation study, two rates of FGDG (33.6 Mg ha?1 and 66.2 Mg ha?1), two rates of biochar made from sugar beet (Beta vulgaris L.) pulp (16.8 Mg ha?1), and one rate of FGDG combined with one rate of biochar (33.6 Mg ha?1 ea.) were applied to a sodic soil. Soil physicochemical properties, including cationic exchange, pH, electrical conductivity (ECe), sodium adsorption ratio (SARe), total organic carbon (TOC), water retention, and soil respiration rate, were assessed during and at the end of the incubation period. Addition of FGDG to sodic soil increased ECe from 3.5 to 8.4 dS m?1 and decreased SARe from 16 to 9. Biochar addition to sodic soil increased TOC from 62.2 to 99.5 μg g?1 and increased soil respiration rate (mg C kg?1 soil day?1) on every measurement period. When FGDG and biochar were both added to the sodic soil, TOC did not significantly improve; however, ECe increased from 3.5 to 7.7 dS m?1, SARe decreased from 16 to 9, and soil respiration rate increased for all measurements. The results confirm there is potential for FGDG and biochar to reclaim sodic soils alone, and applied in combination.  相似文献   

10.
Salt-affected soils are widespread, particularly in arid climates, but information on nutrient dynamics and carbon dioxide (CO2) efflux from salt-affected soils is scarce. Four laboratory incubation experiments were conducted with three soils. To determine the influence of calcium carbonate (CaCO3) on respiration in saline and non-saline soils, a loamy sand (6.3% clay) was left unamended or amended with NaCl to obtain an electrical conductivity (EC) of 1.0 dS?m?1 in a 1:5 soil/water extract. Powdered CaCO3 at rates of 0%, 0.5%, 1.0%, 2.5%, 5.0% and 10.0% (w/w) and 0.25-2 mm mature wheat residue at 0% and 2% (w/w) were then added. Cumulative CO2-C emission from the salt amended and unamended soils was not affected by CaCO3 addition. To investigate the effect of EC on microbial activity, soil respiration was measured after amending a sandy loam (18.8% clay) and a silt loam (22.5% clay) with varying amount of NaCl to obtain an EC1:5 of 1.0–8.0 dS?m?1 and 2.5 g glucose C?kg?1 soil. Soil respiration was reduced by more than 50% at EC1:5?≥?5.0 dS?m?1. In a further experiment, salinity up to an EC1:5 of 5.0 dS?m?1 was developed in the silt loam with NaCl or CaCl2. No differences in respiration at a given EC were obtained between the two salts, indicating that Na and Ca did not differ in toxicity to microbial activity. The effect of different addition rates (0.25–2.0%) of mature wheat residue on the response of respiration to salinity was investigated by adding NaCl to the silt loam to obtain an EC1:5 of 2.0 and 4.0 dS?m?1. The clearest difference between salinity levels was with 2% residue rate. At a given salinity level, the modelled decomposition constant ‘k’ increased with increasing residue addition rate up to 1% and then remained constant. Particulate organic carbon left after decomposition from the added wheat residues was negatively correlated with cumulative respiration but positively correlated with EC. Inorganic N (NH 4 + -N and NO 3 ? -N) and resin P significantly decreased with increasing salinity. Resin P was significantly decreased by addition of CaCl2 and CaCO3.  相似文献   

11.
In the Far West Texas region in the USA, long‐term irrigation of fine‐textured valley soils with saline Rio Grande River water has led to soil salinity and sodicity problems. Soil salinity [measured by saturated paste electrical conductivity (ECe)] and sodicity [measured by sodium adsorption ratio (SAR)] in the irrigated areas have resulted in poor growing conditions, reduced crop yields, and declining farm profitability. Understanding the spatial distribution of ECe and SAR within the affected areas is necessary for developing management practices. Conventional methods of assessing ECe and SAR distribution at a high spatial resolution are expensive and time consuming. This study evaluated the accuracy of electromagnetic induction (EMI), which measures apparent electrical conductivity (ECa), to delineate ECe and SAR distribution in two cotton fields located in the Hudspeth and El Paso Counties of Texas, USA. Calibration equations for converting ECa into ECe and SAR were derived using the multiple linear regression (MLR) model included in the ECe Sampling Assessment and Prediction program package developed by the US Salinity Laboratory. Correlations between ECa and soil variables (clay content, ECe, SAR) were highly significant (p ≤ 0·05). This was further confirmed by significant (p ≤ 0·05) MLRs used for estimating ECe and SAR. The ECe and SAR determined by ECa closely matched the measured ECe and SAR values of the study site soils, which ranged from 0·47 to 9·87 dS m−1 and 2·27 to 27·4 mmol1/2 L−1/2, respectively. High R2 values between estimated and measured soil ECe and SAR values validated the MLR model results. Results of this study indicated that the EMI method can be used for rapid and accurate delineation of salinity and sodicity distribution within the affected area. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

12.
Abstract

Texture and salt type can influence the relationships between saturated paste electrical conductivity (ECe) and EC of other soil/water ratios. The objectives of this study were to develop and validate relationships among ECe, EC1∶2, and EC1∶5 for soils in Yazd Province, and evaluate the effects of texture and gypsum on those relationships. Two hundred thirty‐six soil samples were collected, of which 200 were used to develop and 36 were used to validate the models. The soils were divided into two textural categories, coarse and fine, and two categories, with and without gypsum. The 1∶2 procedure predicted ECe of slightly more than 1∶5. Gypsum content had stronger impact on the accuracy of models in predicting ECe than texture. The ECe=4.0723EC1∶2?5.7135 and ECe=3.5142EC1∶2+0.7615 models are recommended for soil with and without gypsum, respectively. The methodology can be implemented in any other region, particularly if gypsum is present.  相似文献   

13.
In the oldest commercial wine district of Australia, the Hunter Valley, there is the threat of soil salinization because marine sediments underlie the area. To understand the risk requires information about the spatial distribution of soil properties. Electromagnetic (EM) induction instruments have been used to identify and map the spatial variation of average soil salinity to a certain depth. However, soils vary with depth dependent on soil forming factors. We collected data from a single‐frequency and multiple‐coil DUALEM‐421 along a toposequence. We inverted this data using EM4Soil software and evaluated the resultant 2‐dimensional model of true electrical conductivity (σ – mS/m) with depth against electrical conductivity of saturated soil pastes (ECp – dS/m). Using a fitted linear regression (LR) model calibration approach and by varying the forward model (cumulative function‐CF and full solution‐FS), inversion algorithm (S1 and S2), damping factor (λ) and number of arrays, we determined a suitable electromagnetic conductivity image (EMCI), which was optimal (R2 = 0.82) when using the full solution, S2, λ = 3.6 and all six coil arrays. We conducted an uncertainty analysis of the LR model used to estimate the electrical conductivity of the saturated soil‐paste extract (ECe – dS/m). Our interpretation based on estimates of ECe suggests the approach can identify differences in salinity, how these vary with parent material and how topography influences salt distribution. The results provide information leading to insights into how soil forming factors and agricultural practices influence salinity down a toposequence and how this can guide soil management practices.  相似文献   

14.
Vegetative bioremediation of saline calcareous soil (EC1:1 11.01 dS m?1) was practised through growing fodder beet (Beta Beta vulgaris var. magnum) and millet (Panicum spp.) in soil columns. Beet was grown at a planting density of 4427 plants m?2, whereas millet was grown at two planting densities: 5202 (M1) and 8928 (M2) plants m?2. Some plants were irrigated with 233 μ S cm?1 water throughout the experiment (70 days), while for others non-saline water was replaced with saline water (2.52 dS m?1) at the middle of the experiment. The control was leaching of uncropped soil. Beet had higher ash content and efficiently extracted higher amount of salts (particularly Na and Cl) along with their aboveground biomass than millet under the two irrigation regimes. Millet grown at high planting density had higher ash content and extracted higher amount of salts (particularly Cl) than those at low planting density. Bioremediation, particularly in the case of millet (M1), considerably enhanced soil hydraulic conductivity as compared with leaching treatment; thus, facilitating the removal of some soluble salts beyond the root zone. Accordingly, soil electrical conductivity was considerably decreased by 54–69% compared with the untreated soil. It is concluded that mainly fodder beet is a potential candidate for efficient bioremediation of saline calcareous soils.

  相似文献   

15.
In the range of volumetric water content, θ, from about 0.12 cm3 cm–3 to saturation the relation between bulk electrical conductivity, Cb, and bulk electrical permittivity, ε, of mineral soils was observed to be linear. The partial derivative ?Cb/?ε appeared independent of the moisture content and directly proportional to soil salinity. We found that the variable Xs = ?Cb/?ε determined from in situ measurements of Cb(θ > 0.2) and ε(θ > 0.2) can be considered as an index of soil salinity, and we call it the ‘salinity index’. Knowing the index and sand content for a given soil we could calculate the electrical conductivity of the soil water, Cw, which is a widely accepted measure of soil salinity. The two variables from which the salinity index can be calculated, i.e. Cb and ε, can be read simultaneously from the same sensor by time-domain reflectometry. Quantities and symbols a constant /dS m–1 b constant c constant /dS m–1 C b electrical conductivity of bulk soil /dS m–1 C b′ constant equal to 0.08 dS m–1 C s electrical conductivity of a solution used to moisten soil samples /dS m–1 C w electrical conductivity of soil water defined as the soil salinity /dS m–1 C wref reference salinity (that truly existing) resulting from the procedure of moistening samples, expressed as Cs + Cr/dS m–1 C r baseline value of Cs due to residual soluble salts present in the soil /dS m–1 d constant D dry soil bulk density /g cm–3 l slope r ratio S sand content /% by weight t time /s X s salinity index /dS m–1 X si initial salinity index when distilled water is used to moisten soil samples /dS m–1 Y a moisture-independent salinity-dependent variable /dS m–1 z coordinate along direction of flow of the soil solution ε′ constant equal to 6.2 ε relative bulk electrical permittivity (dielectric constant) of the soil θ volumetric water content determined thermogravimetrically using oven-drying /cm3 cm–3  相似文献   

16.
Irrigation with low-quality water may change soil hydraulic properties due to excessive electrical conductivity (ECw) and sodium adsorption ratio (SARw). Field experiments were conducted to determine the effects of water quality (ECw of 0.5–20 dS m?1 and SARw of 0.5–40 mol0.5 l?0.5) on the hydraulic properties of a sandy clay loam soil (containing ～421 g gravel kg?1 soil) at applied tensions of 0–0.2 m. The mean unsaturated hydraulic conductivity [K(ψ)], sorptive number (α) and sorptivity coefficient (S) varied with change in ECw and SARw as quadratic or power equations, whereas macroscopic capillary length, λ, varied as quadratic or logarithmic equations. The maximum value of K(ψ) was obtained with a ECw/SARw of 10 dS m?1/20 mol0.5 l?0.5 at tensions of 0.2 and 0.15 m, and with 10 dS m?1/10 mol0.5 l?0.5 at other tensions. Changes in K(ψ) due to the application of ECw and SARw decreased as applied tension increased. Analysis indicated that 13.7 and 86.3% of water flow corresponded to soil pore diameters <1.5 and >1.5 μm, respectively, confirming that macropores are dominant in the studied soil. The findings indicated that use of saline waters with an EC of <10 dS m?1 can improve soil hydraulic properties in such soils. Irrigation waters with SARw < 20 mol0.5 l?0.5 may not adversely affect hydraulic attributes at early time; although higher SARw may negatively affect them.  相似文献   

17.
Drought is a serious concern in many parts of the world, including in California, where paucity of available irrigation water has impaired crop production and soil health through salt accumulation. With extending water and salinity crises, there is a need for advanced salt and vegetation management. To develop more efficient management solutions, Slingram electromagnetic investigations and stochastic and statistical analyses were performed for determining optimal vegetable yields in a salt-affected farmland. The Slingram results were evaluated using multi-linear regression analyses, and the yield and salinity were characterized for central tendency, variance, distributions and symmetry. The yields of two studied vegetable crops, lettuce and tomato, increased with decreasing salinity load. The average lettuce and tomato yield potentials were 55 and 75%, respectively. The minimum yield potential for tomato was 9.5 times higher than that for lettuce. The mode value for conductivity (ECe) was 650 mS m?1, which corresponded to 50% yield loss. The yield loss was <10% in locations with ECe < 250 mS m?1. In zones with ECe > 850 mS m?1, the yield reductions for lettuce and tomato reached up to 96 and 60%, respectively. About 57 and 82% of the field area could be limited to 20% yield potentials for tomato and lettuce, respectively. Lettuce had a higher cost benefit than tomato albeit with a greater yield potential of the latter crop. By delineating the spatial contours of salt-induced yield variability, vegetables can be grown in segmented soil zones based on salinity levels.  相似文献   

18.
We have determined electrical conductivity (Ee) and total dissolved salts (S) in saturation extracts from 39 soil samples from the Baza basin (Province of Granada, south-east Spain). Ee ranged from 2.8 to 110dS m?3, and S from 2 to 444 8 dm?3. The relationship between S and Ee was not linear. When the saturation extracts were diluted with progressively larger quantities of distilled water and their electrical conductivity calculated (Eec) with the equation where Ed and Ew are the conductivity of the diluted extract and the distilled water and f is the dilution factor, the relationship between S and Eec tended to become linear. The highest linear correlation coefficient relating S (mg dm?3) and Eec (dS m?1) was reached when Eec, values were calculated for dilutions with a conductivity (Ed) between 0.1 and 0.3 dS m?1 (E*ec). The regression equation was S= 490 E*ec with r2= 0.999. This relationship can be used in all saturation extracts, regardless of the concentration and type of ions present.  相似文献   

19.
Greenhouse experiment was conducted to investigate the effect of different levels of irrigation water salinity (0.5, 2.5, 5 and 7.5 dS m?1) and wheat straw biochar (0%, 1.25%, 2.5%, and 3.75% w/w) on growth and yield of faba been using complete randomized design with three replications. Stomatal conductance (green canopy temperature) of faba bean increased (decreased) by application of biochar at each salinity level. The results showed increasing salinity to 2.5 dS m?1 at zero biochar application increased the seed yield through osmotic adjustment, while by declining the osmotic potential, the nutritional values of biochar caused the seed yield to increase by increasing salinity to 5 dS m?1. The root length density and root dry weight density in 0–8 cm soil layer declined under application of 3.75% w/w biochar in all salinity levels in comparison with that obtained in 2.5% w/w biochar, due to higher saline condition of the soil as result of higher biochar application. The results showed that addition of 2.5% w/w biochar can significantly mitigate salinity stress due to its high salt sorption capacity and by increasing potassium/sodium ratio in the soil. In general, since 2.5 % w/w biochar and salinity of 5 dS m?1 increased dry seed yield and irrigation water productivity compared with that obtained in control (B0S0.5), these levels are recommended to improve faba bean growth and yield; however, these levels have to be evaluated under field conditions.  相似文献   

20.
The aim of this study was to generate models to predict the salinity of the soils in the geothermal zone which is located in Michoacán, México, over space and time. Systematic sampling was performed at locations 400 m apart with a sampling period every 48 days. At each site, two soil samples, from depths of 0–30 cm and 30–60 cm, were collected and analysed in laboratory. Regression-Kriging was used to make spatial predictions of the electrical conductivity of soil (ECs). Spherical and Gaussian theoretical models fit the experimental semivariograms. The results showed that the soil samples ranged from slightly saline (2.1–4 dS m?1) to strongly saline (8.1–16 dS m?1). In addition, the ECs was greater at a depth of 30–60 cm than it was at a depth of 0–30 cm. The ECs decreased from more than 8.0 dS m?1 to less than 4.0 dS m?1 after the first sampling period.  相似文献   

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