Compressive properties of some Swedish and Danish structured agricultural soils measured in uniaxial compression tests

Soil compaction is recognized as a threat to long‐term productivity of agricultural soils and as a cause of environmental problems such as flooding. The use of models to establish strategies for prevention of soil compaction is hampered by lack of model input parameters describing soil mechanical properties. This paper presents the compressive properties N (specific volume at σ = 1 kPa on the virgin compression line), C_c (compression index) and C_r (recompression index) obtained from uniaxial compression testing of 69 individual soil layers and investigates the relationships between these properties and readily quantifiable soil parameters. No correlation was found between compressive properties and soil texture. Instead, N, C_c and C_r were positively correlated to the initial specific volume (v₀). This suggests that compressive properties are more strongly affected by soil structure than by soil texture. Dependency of compressive properties on v₀ could not be expected from classical soil compressive behaviour theory but suggests modifications to the theory of soil unloading‐reloading behaviour. We suggest that the latter is dependent on time between unloading and reloading.     

Ermittlung des Spannungszustandes von Böden aus Werten des Eindringwiderstandes von Sonden

Evaluation of the soil consolidation state by using data from penetration resistance probes Penetration resistance data (EW) from handdriven equipment are easily obtainable because the equipment is simple, cheap, and easily carriable. Measurements are performed quickly without extensive destruction of the site. It is the only method to measure soil strength directly and in situ. Therefore, it is worthwhile to propose an interpretation of the results in order to obtain more conclusive statements on the structural soil state. The procedure applied in our study consists in assigning EW values to the principal stress σ_x and in using an auxiliary construction for the vertical component (σ_z ) as a function of penetration depth. The EW value obtained at the final soil depth is assumed to represent stresses at rest, i.e., K₀ = σ_x/σ_z = 1. Drawing a straight line from this point towards the origin of the coordinates EW and soil depth supplies values of the hydrostatic condition for each depth; e.g., values for σ_z are available for each depth. The coefficient for the equivalent stress at rest (K_0E) per depth can now be calculated simply by comparing the measured EW values with the assumed (hydrostatic) vertical depth function of EW. From a total volume of 29 sets of EW versus depth relations, means and standard deviation of K_0E are presented for arable and forest soils from central Europe. K_0E of forest soils tends to be close to 1 showing approximately normal compaction. In arable sites, K_0E > 2 prevail, indicating precompation. These results confirm the general feasibility of the approach to evaluate the compaction state of soil from EW data. Examples are given to show the K_0E characteristics for special cases of mechanical stress situations.     

Combination of micro suction cups and time-domain reflectometry to measure osmotic potential gradients between bulk soil and rhizosphere at high resolution in time and space

A prerequisite to investigate the importance of osmotic potential (Ψ_o) in relation to matric potential (Ψ_m) in the soil for water uptake is the existence of a method that measures the temporal and spatial dynamics of Ψ_o in the vicinity of roots. One method for measuring Ψ_oin situ is the collection of soil solution with micro suction cups, the spatial resolution of which is suitable for rhizosphere studies. A major drawback of soil solution sampling is the disturbance of soil solution equilibrium, which makes frequent measurements impossible, so another method is required to provide information on the temporal dynamics of Ψ_o. The time‐domain reflectometry (TDR) technique might be suitable as the signal attenuation (σ) shows a close linear correlation with the salt concentration for a known soil water content. The temporal resolution of the TDR technique is high and the measurement has no impact on soil solution equilibrium. However, the spatial resolution of the TDR technique is too coarse to be used on its own in rhizosphere studies. We used a combination of TDR (fine temporal resolution) and micro suction cups (fine spatial resolution) to measure Ψ_o in a model system with Zea mays grown in quartz substrates. Osmotic potential changed continuously with time, and a steep gradient between bulk soil and the root compartment developed during the 39‐day growing period. The steepest gradient measured over a distance of 6 mm across the nylon net, separating the bulk soil from the root compartment, was ?365 kPa. The combination of both methods made it possible to extend the time interval between micro suction cup samplings and thus minimize the impact of sampling on soil solution equilibrium. Problems of separate calibration were avoided by calibrating the TDR measurements against the results obtained with the micro suction cups within the same experiment.     

Comparison of Iron Oxide–Impregnated Paper Strips with Other Extractants in Determining Available Soil Phosphorus

Abstract

Iron oxide–coated strips (P_i) can serve as a sink to continuously remove phosphorus (P) from solution. In this way, P extraction is analogous to the P absorption by plant roots. The objective of this study was to compare the iron oxide–coated paper strips with other chemical extraction methods to estimate the plant P availability for corn (Zea mays) growing in the greenhouse in some soils of Hamadan province of Iran. Sixteen soil samples with different physicochemical properties were analyzed for available P using Olsen, Colwell, Mehlich‐1, 0.01 M CaCl₂, AB‐DTPA, and 0.1 M HCl methods and p_i. Furthermore, the effects of two P levels (0 and 200 mg P kg^?1) on the plant indices (P uptake, relative yield, and plant responses) were studied in a greenhouse experiment using 10 soil samples. The results showed that the amount of extractable P decreased in the order of 0.01 M CaCl₂<AB‐DTPA<p_i<Olsen<Colwell<Mehlich‐1<0.1 M HCl. The amount of P extracted by the p_i method was significantly correlated with other extractants. The amounts of P extracted by all chemical methods were significantly correlated. The results of a pot experiment showed that the amount of P extracted by the p_i method was significantly correlated with the plant P uptake. However, the other methods were not significantly correlated with P uptake. The results of this experiment showed that p_i method was able to predict the plant availability of soil P.     

A new technique for measuring broadband dielectric spectra of undisturbed soil samples

A new coaxial line cell for the determination of dielectric spectra of undisturbed soil samples was developed based on a 1.625‐inch ‐ 50 Ω coaxial system. Undisturbed soil samples were collected from a soil profile of the Taunus region (Germany) and capillary saturated followed by a step‐by‐step de‐watering in a pressure plate apparatus as well as oven‐drying at 40°C. The resultant water contents of the soil samples varied from saturation to air‐dry. Permittivity measurements were performed within a frequency range from 1 MHz to 10 GHz with a vector network analyser technique. Complex effective relative permittivity or electrical conductivity was obtained by combining quasi‐analytical and numerical inversion algorithms as well as the parameterizing of measured full set S‐parameters simultaneously under consideration of a generalized fractional dielectric relaxation model (GDR). The measurement of standard materials shows that the technique provides reliable dielectric spectra up to a restricted upper frequency of 5 GHz. For the soil samples investigated, the real part of complex effective relative permittivity ?′_r,eff and the real part of complex effective electrical conductivity σ′_eff decreased with increasing matric potential or decreasing water contents. Soil texture and porosity affect the dielectric behaviour at frequencies below 1 GHz. For frequencies above 1 GHz minor texture effects were found. The presence of organic matter decreases ?′_r,eff and σ′_eff. At 1 GHz, the empirical model of Topp et al. (1980) is in close agreement with the experimentally determined real part of the effective permittivity with RMSEs ranging from 1.21 for the basal periglacial slope deposit and 1.29 for bedrock to 3.93 for the upper periglacial slope deposit (Ah). The comparison of the experimental results with a semi‐empirical dielectric mixing model shows that data, especially for the organic‐free soils, tend to be under‐estimated below 1 GHz. The main advantage of the new method compared with conventional impedance and coaxial methods is the preservation of the natural in‐situ structure and properties such as bulk density of the investigated soil samples.     

A soil quality index based on the equilibrium between soil organic matter and biochemical properties of undisturbed coniferous forest soils of the Pacific Northwest

Recent studies have suggested that the organic matter contents of undisturbed soils (under natural vegetation) are in equilibrium with biological and biochemical properties. Accordingly, we hypothesised that such equilibria should be disrupted when soils are subjected to disturbance or stress, and that measurement of this disruption can be expressed mathematically and used as a soil quality index. In this study, we evaluated these hypotheses in soils from the H.J. Andrews Experimental Forest in Oregon. Both O and A horizons were sampled from nine sites in Spring 2005 and Fall 2006. Soil samples were analyzed for enzyme activities (phosphatase, β-glucosidase, laccase, N-acetyl-glucosaminidase, protease and urease), and other biological and chemical properties including N-mineralization, respiration, microbial biomass C (MBC), soil organic carbon (SOC) and total nitrogen content. In addition, soil samples from one old-growth site were manipulated in the laboratory to either simulate chemical stresses (Cu addition or pH alteration) or physical disturbances (wet-dry or freeze-thaw cycles). The results showed variation in biological and biochemical soil properties that were closely correlated with SOC. Multiple regression analysis of SOC levels against all soil properties showed that a model containing only MBC and phosphatase activity could account for 97% of the SOC variation among the sites. The model fit was independent of spatial and temporal variations because covariates such as site, stand age, sampling date, and soil horizon were found to be not statistically significant. Although the application of stress/disturbance treatments inconsistently affected most of the individual biochemical properties, in contrast, the ratio of soil C predicted by the model (C_p), and soil C measured (C_m) was consistently reduced in soils submitted to at least one level of stress and disturbance treatments. In addition, C_p/C_m was more affected in soils submitted to wet-dry cycles and Cu contamination than to freeze-thaw cycles or shifts in soil pH. Our results confirm previous evidence of a biochemical balance in high quality undisturbed soils, and that this balance is disrupted when the soil is submitted to disturbances or placed under stress conditions. The C_p/C_m ratio provides a simple reference value against which the degrading effects of pollutants or management practices on soil quality can be assessed.     

A profiling TDR probe for water content and electrical conductivity measurements of soils

Measurements of water content profiles are of great interest in hydrology and soil science. Time domain reflectometry (TDR) is a well‐established method for water content measurements; however, most TDR probe designs are suitable for measurements in only a small soil volume. In this article, a 1‐m long TDR profiling probe with five measurement sections is described. Unlike most other previous profiling probes, our probe allows for both dielectric permittivity (ε) and electrical conductivity (σ_a) measurements. The accuracy of the ε and σ_a measurements was excellent; the precision of the measurements was, however, significantly poorer than with a 0.20‐m long standard three rod TDR probe. The new probe was installed in a field and successfully measured water content profiles during the growing season of 2009. During an infiltration experiment it was shown that because of its geometry, the profiling probe over‐estimated the wetting‐front velocity. At a 0.10‐m depth, the over‐estimation was almost 30%. The over‐estimate will be less significant at greater depths.     

A mathematical model for the adsorption of water vapor by soils

A two-parameter mathematical model based on some physical assumptions was developed for the adsorption of water vapor by soils: W = W _mh[(p/p ₀) − (p/p ₀)³ + (p/p ₀)⁶] + W _res. It was shown that one of the model’s parameters is close to a conventional soil-hydrological constant, namely, the maximum hygroscopic moisture, or maximum hygroscopicity W _mh. The second parameter reflects the residual water content W _res as the content of immobilized water, which is bound to the most active part of the adsorbing surface, is adsorbed at the initial stage of adsorption (0 ≤ p/p ₀ ≤ 0.05), and later does not participate in the adsorption processes. Methods were proposed for the differential calculation of singular points and parameters of the model corresponding to the characteristic physical phenomena of water vapor adsorption in soils. The model was tested for the quantitative assessment of the interaction between the soil solid phase and the water vapor in different soils (a soddy-strongly podzolic soil, an ordinary chernozem, a chestnut soil, and a medium-columnar solonetz). A method was proposed for calculating the integral adsorption energy E _max of the soil solid phase-water vapor interaction. It was shown that the E _max values are determined by the physicochemical properties of the soils and characterize the capacity of the separate soil horizons for adsorbing water vapor. The relationship of the integral adsorption energy of the soils with the relative pressure of the water vapor and the water content was studied.     

Comparison of Various Chemical Extraction Methods used for Determination of the Available Iron Amounts of Calcareous Soils

This study was conducted to compare the most appropriate method for the evaluation of available iron (Fe) status of calcareous soils by using nine different chemical extraction methods. Leaf and soil samples were collected from nine peach (Prunus persica L.) orchards, each of which included green, slightly chlorotic, and severely chlorotic peach trees. According to the chlorosis degrees of the leaves, total and active Fe contents and some soil properties were determined. Relationships between these parameters and Fe amounts obtained from the methods were correlated. Among the methods tested, method 3 (M3) [0.05 N hydrochloric acid (HCl) + 0.025 N sulfuric acid (H₂SO₄)] and method 8 (M8) 0.05 M ethylenediaminetetraacetic acid (EDTA) (pH 7.0) were the most suitable methods to indicate the available Fe status of the soils.     

Assessment of plant nutrients’ dynamics in organically and conventionally managed soils by means of different extraction methods

The aim of this study was to investigate what kind changes in the soil fertility parameters occur depending on different farming methods. The field experiment was performed on sandy loam Luvisol during 2008–2014. The following treatments were carried out: organic (ORG), organic with farmyard cattle manure (ORGFYM) and conventional with farmyard cattle manure and mineral fertilizers (CONFYM). Soil samples were collected yearly in September and analyzed for P, K, Mg and Ca by the Mehlich III method. In parallel, ammonium lactate extractable P and K (AL method), and ammonium acetate extractable Mg and Ca (NH₄OAc-method) were determined. The Pearson correlation coefficients between the analysis results achieved by the Mehlich III method and alternative methods were calculated. In all the treatments, no significant changes in soil Corg content were established over seven years. A significant (p?AL in the soil but considerable decrease in the soil K_AL content was revealed. The application of cattle manure (60?t?ha^?1 for the 5-year crop rotation) in both organic and conventional treatments sustained the status of available nutrients in the soil. The Pearson correlation coefficients between Mehlich III and AL methods for P (r?=?0.770, p?r?=?0.922, p?4OAc-methods was found in the case of Mg (r?=?0.951, p?r?=?0.841, p?Mehlich III/P_AL quotient was inversely proportional with the Ca_{Mehlich III} values.     

Analysis of Citrus Orchard Efficiency in Relation to Soil Properties

ABSTRACT

Orchard efficiency (OE) is one of the indices of evaluating the sustainability in production behavior of citrus orchards. A wide range of soil properties broadly categorized into particle size distribution, water soluble and exchangeable cations, and soil available nutrients were investigated in relation to efficiency of Nagpur mandarin (Citrus reticulata Blanco) orchards established on smectite rich three soil orders (Entisols, Inceptisols, and Vertisols) representing 18 locations of central India. The soil properties, viz., free calcium carbonate (CaCO₃), clay content, water soluble- and exchangeable-calcium (Ca^{2 +}), available nitrogen (N), phosphorus (P), and zinc (Zn) contributed significantly towards variation in OE. The threshold limit of these limiting soil properties was further established using multivariate quadratic regression models as: 132.1 g kg^{? 1} free CaCO₃, 418.1 g kg^{? 1} clay, 149.9 mg L^{? 1} water soluble Ca^{2 +}, 25.9 cmol(p⁺) kg^{? 1} exchangeable Ca^{2 +}, 114.6 mg kg^{? 1} available N, 12.8 mg kg^{? 1} available P, and 0.96 mg kg^{? 1} available Zn in relation to optimum OE of 82.1%. These reference values were very close to those obtained from best fit models, and could be effectively utilized in addressing soil related production constraints for precision-aided citriculture.     

Alternative methods in the development of pedotransfer functions for soil hydraulic characteristics

Soil hydraulic properties are needed in the modeling of water flow and solute movement in the vadose zone. Pedotransfer functions (PTFs) have received the attention of many researchers for indirect determination of hydraulic properties from basic soil properties as an alternative to direct measurement. The objective of this study was to compare the performance of cascade forward network (CFN), multiple-linear regression (MLR), and seemingly unrelated regression (SUR) methods using prediction capabilities of point and parametric PTFs developed by these methods. The point PTFs estimated field capacity (FC), permanent wilting point (PWP), available water capacity (AWC), and saturated hydraulic conductivity (Ks) and the parametric PTFs estimated the van Genuchten retention parameters. A total of 180 soil samples was extracted from the UNSODA database and divided into two groups as 135 for the development and 45 for the validation of the PTFs. The model performances were evaluated with three statistical tools: the maximum error (ME), the model efficiency (EF), and the D index (D) using the observed and predicted values of a given parameter. Despite the fact that the differences among the three methods in prediction accuracies of the point and parametric PTFs were not statistically significant (p > 0.05) except θ_r and α (p < 0.05) based on the ANOVA test, overall MLR and SUR were somewhat better than CFN in prediction of the point PTFs, whereas CFN performed better than the other two methods in prediction of the parametric PTFs. The F.F values of FC and θ_r for CFN, MLR, and SUR methods were 0.705. 0.805, 0.795 and 0.356, −0.290, −0.290, respectively, which refer to the best and worst predictions. Properties (Ks, θ_r, α) having some difficulty in prediction were better predicted by CFN and SUR methods, where these methods predict all hydraulic properties from basic soil properties simultaneously rather than individually as in MLR. This suggests that multivariate analysis using such functional relationships between hydraulic properties and basic soil properties can be utilized in developing more accurate point and parametric PTFs with less time and effort.     

Microcalorimetric evaluation of soil microbiological properties under plant residues and dogmatic water gradients in Red soil

A study of 6 months duration was carried out to investigate the effect of water regimes and organic amendments on the soil microbial biomass and microbial population under Red soil collected from Hunan Providence, China. The soil microbial biomass and population were measured with traditional methods and results obtained by conventional methods, corroborated with microcalorimetry. The incorporation of rice (Oryza sativa L.) straw (RS) and green manure (GM), especially at high rates, enhanced the soil microbial activities. We observed that the use of GM exhibited more significant stimulating effects on microbial activities than RS. Similarly, water regimes, 25% (W1) and 200% (W2) of water holding capacity, also had significant effects on microbial activities. Comparing the effects of water levels, we noticed that W2 had a significant negative influence on soil microbial biomass and population. To compare the results of conventional methods and to check the sensitivity of microcalorimetry, the thermodynamic parameters, microbial growth rate constant (k), total heat evolution (Q), peak height (P_max) and peak time (t_max) were calculated. Highest P_max, k and Q were observed in GM treatments at water regime W1, while highest t_max values were recorded in CK (control) and RS treatments at W2. The microcalorimetric parameters, P_max, k and Q were positively correlated, whereas t_max negatively linked with microbial biomass and population at p < 0.01. Our results suggest that microcalorimetry successfully verified the results obtained from customary methods and microcalorimetric parameters P_max, t_max, Q and k proved that they are highly sensitive to microbial properties and could be used as indices of microbial community shifts and activities in soil ecosystems.     

基于地类分层的土壤有机质光谱反演校正样本集的构建

以江汉平原滨湖地区不同土地利用类型的土壤样本为例,比较了基于目标土壤理化性质的浓度梯度法、扩展的基于多种理化性质的综合法(P-KS)、基于光谱信息的KS法、最邻近样本去除法(reduce nearest neighbor samples,RNNS)法和基于浓度分层并结合光谱信息的C-KS、C-RNNS法,基于地类分层再结合上述方法,构建具有不同层次土壤信息代表性的校正集,采用偏最小二乘回归法,建立土壤有机质可见光/近红外光谱反演模型。结果表明,具有单一代表性的浓度梯度法、KS法、RNNS法难以建立适用模型;具有光谱与理化性质二元代表性的C-KS方法模型预测精度得到了明显的提升,相对分析误差(ratio of performance to standard deviation,RPD)为1.66;考虑土地利用类型后,浓度梯度法、RNNS法与C-KS法模型预测精度有明显的提升,RPD分别达到了1.84、1.51、1.75,模型具有良好的适用性。说明具有多层次土壤信息代表性的校正集构建方法对提高土壤有机质可见光/近红外光谱反演模型的适用性具有较好作用。     

Evapotranspiration and regional probabilities of soil moisture stress in rainfed crops, southern India

The long-term probability of soil moisture stress in rainfed crops was mapped at 0.5° resolution over the Krishna River basin in southern India (258,948 km²). Measurements of actual evapotranspiration (E_a) from 90 lysimeter experiments at four locations in the basin were used to calibrate a non-linear regression model that predicted the combined crop coefficient (K_cK_s) as a function of the ratio of seasonal precipitation (P) to potential evapotranspiration (E_p). Crops included sorghum, pulses (mung bean, chickpea, soybean, pigeonpea) and oilseeds (safflower and sunflower). E_p was calculated with the Penman–Monteith equation using net radiation derived from two methods: (1) a surface radiation budget calculated from satellite imagery (E_pSRB) and (2) empirical equations that use data from meteorological stations (E_pGBE). The model of K_s as a function P/E_p was combined with a gridded time series of precipitation (0.5° resolution, 1901–2000) and maps of E_pSRB to define the probability distributions of P, P/E_p and K_s for sorghum at each 0.5° cell over the basin. Sorghum, a C4 crop, had higher E_a and K_s values than the C3 plants (oilseeds, pulses) when precipitation was low (P < 1 mm d⁻¹) but lower maximum E_a rates (3.3–4.5 mm d⁻¹) compared with C3 crops (oilseeds and pulses, 4.3–4.9 mm d⁻¹). The crop coefficient under adequate soil moisture (K_c) was higher than the FAO-56 crop coefficients by up to 56% for oilseeds and pulses. The seasonal soil moisture coefficient (K_s) for sorghum ranged from 1.0 under high rainfall (July–October) to 0.45 in dry seasons (November–March), showing strong soil moisture controls on E_a. E_pSRB calculated at the lysimeter stations was 4–20% lower than E_pGBE, with the largest difference in the dry season. K_c derived from E_pSRB was only slightly (2–4%) higher than K_c derived from E_pSRB, because the maximum E_a occurred during the monsoon when the differences between E_pSRB and E_pGBE were small. Approximately 20% of the basin area was expected to experience mild or greater soil moisture stress (K_s < 0.80) during the monsoon cropping season 1 year in every 2 years, while 70% of the basin experienced mild or greater stress 1 year in 10. The maps of soil moisture stress provide the basis for estimating the probability of drought and the benefits of supplemental irrigation.     

A Modification to the Adams‐Evans Soil Buffer Determination Solution

Abstract

Many soil analysis labs routinely determine lime requirement of acidic soils using different buffer solutions for optimum plant growth. The Adams‐Evans lime determination solution was introduced more than 40 years ago and has been used by many soil analysis labs. Even though many buffer solutions have been developed since then, very little attention has been paid to address the toxic nature of chemicals involved in buffer solutions. The most commonly used buffer solutions, such as the Adams-Evans, Shoemaker‐McLean‐Pratt (SMP), Woodruff, and others, contain p‐nitrophenol, which is toxic to humans and the environment. Use of p‐nitrophenol requires prescribed containment and disposal procedures, that creates extra burden on soil analysis labs that provide their invaluable service at low cost. Replacing p‐nitrophenol with monobasic potassium phosphate (KH₂PO₄), which has similar buffering capacity but with no known toxicity, is beneficial to soil testing labs and the environment. The original Adams‐Evans buffer solution was compared with the modified Adams‐Evans buffer solution with soils of different pH, cation exchange capacity and lime requirement. The linear regression between the buffer pH values and lime recommendations made by Adams‐Evans and the modified Adams‐Evans solutions were highly significant. Thus, the modified Adams‐Evans buffer solution can be used without loss of established recommendation criteria as the original buffer solution.     

Evaluation of certain Ni soil tests for an initial estimation of Ni sufficiency critical levels

Although Ni is officially recognized as an essential micronutrient for all higher plants, the majority of the published research on soil availability of Ni focuses on its hazardous role as a heavy metal. The objective of the study was to evaluate certain Ni soil tests in uncontaminated soils for an initial estimation of its sufficiency critical levels. Nickel was extracted from 30 cultivated soils employing the following extraction methods: DTPA, AB‐DTPA, AAAc‐EDTA, Mehlich‐3, 0.1 M HCl, and 0.1 M HNO₃. Ryegrass (Lolium perenne L.) was grown in pots containing the soils, harvested five times, certain plant parameters were determined, and the Cate–Nelson procedures were used for Ni critical levels determination. Among the six methods, HCl was the least reliable extractant for the evaluation of soil available Ni, whereas the most significant (p ≤ 5%) relationships between Ni concentration or Ni uptake by ryegrass and Ni soil tests were consistently obtained for AAAc‐EDTA or Mehlich‐3 extractable Ni. In many cases, > 80% of the variability of Ni concentration or uptake by ryegrass was explained by these two soil tests without the inclusion of other soil properties that affect Ni bioavailability. Sufficiency critical levels of Ni in soil were ≈ 2 mg kg^–1 for both methods. Consequently, as an initial approach, concentrations of AAAc‐EDTA or Mehlich‐3 extractable Ni < 2 mg kg^–1 are probably a good guide to indicate soils that will respond to Ni fertilization.     

Detecting a leachate plume in an aeolian sand landscape using a DUALEM‐421 induction probe to measure electrical conductivity followed by inversion modelling

Solid waste poses a serious health risk when it is disposed of inadequately because water‐based solutions derived from the decomposition of solid waste products (leachate) can enter groundwater systems via plumes. To assess the public health risk and potential ecological impacts, we require knowledge on the pedological and hydrogeological settings in which waste is disposed. This is particularly the case in coarse textured highly permeable soil. To rapidly collect data, geophysical methods such as direct current (dc) resistivity techniques have been used. Moreover, non‐contact electromagnetic (EM) induction instruments have also been employed. The aim of this research was to demonstrate how the inversion using a 1‐dimensional inversion algorithm with lateral constraints of the apparent electrical conductivity (σ_a) measured in the horizontal coplanar (HCP) and perpendicular co‐planar arrays (PRP) of a DUALEM‐421 EM induction probe can be used to develop a two‐dimensional model of the true electrical conductivity (σ) within a Quaternary aeolian sand in the Tuggerah Soil Landscape southeast of Sydney in Australia. Our results from 2D models of σ accord with estimates of bulk electrical conductivity (σ_b) of a leachate plume and uncontaminated groundwater, the stratigraphy of the Tuggerah soil landscape unit and the depth of sand used to landscape the decommissioned landfill. Further research is needed to determine the origin of the plume and a quasi‐3D modelling approach is applicable.