Proximal Soil Sensing of Low Salinity in Southern Xinjiang, China

Abstract

Measuring the soil salinity using visible and near-infrared (vis–NIR) reflectance spectra is considered a fast and cost-effective method. For monitoring purposes, estimating soils with low salinity measured as electrical conductivity (EC) using vis–NIR spectra is still understudied. In this research, 399 legacy soil samples from six regions of Southern Xinjiang, China with low EC values were used. Reflectance spectra were measured in the laboratory on dried and ground soil samples using a portable vis–NIR spectrometer. By using 10-fold cross-validation, three algorithms–partial least-squares regression (PLSR), random forest (RF), and Cubist–were employed to develop statistical models of EC. The model performance evaluation was obtained by the relative importance of variants. In terms of accuracy assessment of soil EC prediction, the results demonstrated that the Cubist model performed better (R2 = 0.67, RMSE = 0.16 mS/cm, RPIQ = 2.28) than both PLSR and RF. Despite similar variants for modelling, the RF model performed somewhat better than that of the PLSR. Additionally, the 610 nm and 790 nm wavelengths only demonstrated significant promise for predicting low soil EC values when used in the Cubist mode. The current research recommends the use of Cubist to estimate the low soil salinity using the vis–NIR reflectance spectra.

Challenges and Opportunities in Remote Sensing for Soil Salinization Mapping and Monitoring: A Review

“…This method involves constructing a series of decision trees, each with adjusted weights, to produce a model that accurately reflects the patterns in the data [118]. It can be advantageous in cases where the relationship between input variables and the predicted outcome is complex and difficult to discern using traditional statistical models such as soil salinity modeling [119,120]. Nevertheless, this is quite different for geostatistical models [121][122][123], although they rely on statistical assumptions about underlying spatial variability to estimate salinity at unsampled locations.…”

Portable NIR spectroscopy: the route to green analytical chemistry

“…Soil texture characterization is usually carried on manually, being consequently time-consuming. Vis-NIR handheld spectroscopy is preferred as sensor to predict soil characteristics ( Bene et al, 2020 ; Benedet et al, 2020 ; Pham et al, 2021 ; Andrade et al, 2022 ; Naimi et al, 2022 ; Peng et al, 2022 ; Shrestha et al, 2022 ; Teixeira et al, 2022 ; Vohland et al, 2022 ).…”