In irrigated areas, the spectre of soil salinisation is ever‐present. To obtain baseline data to map salt, or the soil electrical conductivity of a saturated soil paste extract (EC_e, dS m⁻¹), we use electromagnetic (EM) data from a survey of EM38 and EM34 data with EM inversion software (EM4Soil). This is because the collected apparent electrical conductivity (EC_a, mS m⁻¹) can be inverted to estimate true electrical conductivity (σ, mS m⁻¹) and correlated with EC_e. To do this we use a quasi‐two dimensional (Q‐2D) model along a pseudo‐transect, which includes seven soil sample locations, to make a linear regression (LR) calibration between σ and EC_e (i.e., EC_e = 0.0122 × σ − 0.0535 [R² = .71]). From the joint inversion of interpolated EM38 and EM34 EC_a across 40,000 ha, a quasi‐three dimensional (Q‐3D) model was then used to predict EC_e. The model was validated using 30 soil sample locations scattered across the area. The agreement between predicted and measured EC_e was moderate (Lin's concordance = 0.59) and conclude that useful information on a reconnaissance scale can be obtained and indicates where more detailed information may be collected to confirm areas of moderate salinity. To better predict EC_e, more EC_a could be collected on smaller grid spacings (i.e., 0.5 km and 1 km in irrigated and dryland areas, respectively). To improve resolving depth of EC_e we recommend including EC_a from a single‐frequency multiple‐coil array DUALEM‐421.

中文翻译：

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利用EM38和EM34数据及反演模型对三维盐度进行勘测规模映射

在灌溉地区，土壤盐渍化的幽灵无处不在。为了获得基线数据以绘制盐或饱和土壤泥浆提取物的土壤电导率（EC _e，dS m ^-1），我们使用来自EM反转软件（EM4Soil）的EM38和EM34数据调查中的电磁（EM）数据）。这是因为可以将收集到的表观电导率（EC _a，mS m ^-1）反转以估算真实电导率（σ，mS m ^-1）并与EC _e相关。为此，我们沿伪断面使用准二维（Q-2D）模型，该模型包括七个土壤样本位置，以在σ之间进行线性回归（LR）校准。和EC _e（即EC _e = 0.0122×σ-0.0535 [ R ² = .71]）。从内插和EM38 EM34 EC的联合反演_一个横跨40000公顷，准三维（Q-3D）模型，然后用其预测EC _È。使用散布在该区域的30个土壤样本位置对模型进行了验证。EC _e的预测值与实测值之间的一致性为中等（Lin一致性= 0.59），并得出结论，可以得到有关侦察规模的有用信息，并指出可以在何处收集更详细的信息以确认中等盐度区域。为了更好地预测EC _e，更多EC _a可以在较小的网格间距上收集（即在灌溉和干旱地区分别为0.5 km和1 km）。为了提高EC _e的分辨深度，我们建议包括单频多线圈阵列DUALEM-421中的EC _a。