Hyperspectral predicting model of soil salinity in Tianjin costal area using partial least square regression

Soil salinization is one of the most devastating land degradation process causing agricultural yields reduction. This paper presents a hyperspectral prediction model of soil salinity using partial least squares regression (PLSR) in Tianjin costal area. Soil spectral reflectance of soil samples varying in salinity was measured using an ASD Field Spec spectrometer. The treated continuum-removed (CR) reflectance and first-order derivative reflectance (FDR) were used and compared to explore the more preferable predicting model of soil salinity, which could detect subtle differences in spectral absorption features compared with original reflectance. The results showed that the soil spectra reflectance got distinct absorption feature with peaks centred at 411 nm, 475 nm, 663 nm, 868 nm, 1100 nm 1250 nm, 1400 nm, 690 nm, 1911 nm, 2206 nm and 2338 nm, representing key bands for soil salt content estimation. Through established Partial Least-Square Regression model based on treated soil spectra, the first derived continuum-removed reflectance was the optimal spectra indexes, prediction accuracy of the optimal PLSR model was 94.4%.Engineering, Electrical & ElectronicGeosciences, MultidisciplinaryRemote SensingEICPCI-S(ISTP)

Review of soil salinity assessment for agriculture across multiple scales using proximal and/or remote sensors

Mapping and monitoring soil spatial variability is particularly problematic for temporally and spatially dynamic properties such as soil salinity. The tools necessary to address this classic problem only reached maturity within the past 2 decades to enable field- to regional-scale salinity assessment of the root zone, including GPS, GIS, geophysical techniques involving proximal and remote sensors, and a greater understanding of apparent soil electrical conductivity (ECa) and multi- and hyperspectral imagery. The concurrent development and application of these tools have made it possible to map soil salinity across multiple scales, which back in the 1980s was prohibitively expensive and impractical even at field scale. The combination of ECa-directed soil sampling and remote imagery has played a key role in mapping and monitoring soil salinity at large spatial extents with accuracy sufficient for applications ranging from field-scale site-specific management to statewide water allocation management to control salinity within irrigation districts. The objective of this paper is: (i) to present a review of the geophysical and remote imagery techniques used to assess soil salinity variability within the root zone from field to regional scales; (ii) to elucidate gaps in our knowledge and understanding of mapping soil salinity; and (iii) to synthesize existing knowledge to give new insight into the direction soil salinity mapping is heading to benefit policy makers, land resource managers, producers, agriculture consultants, extension specialists, and resource conservation field staff. The review covers the need and justification for mapping and monitoring salinity, basic concepts of soil salinity and its measurement, past geophysical and remote imagery research critical to salinity assessment, current approaches for mapping salinity at different scales, milestones in multi-scale salinity assessment, and future direction of field- to regional-scale salinity assessment