Complementarity of proximal and orbital soil sensing for mapping on-farm soil variability
摘要
Despite extensive research in digital soil mapping (DSM), the synergy between diverse sensing platforms remains poorly understood. This study evaluates whether proximal and orbital soil sensing are complementarity for mapping on-farm variability.
MethodsThis study evaluated sensor complementarity and redundancy across three agricultural sites totaling 375 ha. The sensing platforms comprised on-the-go electromagnetic induction (EMI) for apparent electrical conductivity (ECa) and magnetic susceptibility, laboratory-based magnetic susceptibility, x-ray fluorescence (pXRF), and visible-near-infrared diffuse reflectance (VNIR). Additionally, synthetic soil images (SYSI) from Sentinel-2 provided spectral bands and Hue-Saturation-Value conversions. Statistical assessment employed unsupervised techniques, namely Spearman’s correlation, Variance Inflation Factor, and Condition Index, alongside supervised models, including stepwise Multiple Linear Regression, Random Forest, and Partial Least Squares Regression. These two latter models quantified variable importance for clay, silt, sand, total organic carbon, and a soil chemical quality index.
ResultsRedundancy diagnostics revealed that SYSI bands and electromagnetic sensors provided overlapping information, whereas VNIR and pXRF yielded complementary data. While full models exhibited slightly higher predictive accuracy, reduced models utilizing only complementary sensors maintained comparable performance, confirming that a parsimonious variable set is sufficient for soil property prediction. In the absence of spectroscopy (pXRF and VNIR), a combination of ECa with SYSI-Red and Saturation bands were identified as a viable complementary alternative, albeit with lower accuracy than the spectroscopy-based models.
ConclusionThis study establishes that the synergy between VNIR and pXRF sensors optimizes DSM, rendering additional sensors redundant and outperforming single-sensor configurations. Where spectroscopy is unavailable, the joint use of ECa with SYSI-Redand Saturation bands serve as a practical surrogate. Despite a slight reduction in accuracy, this combination remains a viable tool for delineating on-farm soil variability and supporting site-specific management decisions.