An Efficient Approach for Inverting the Soil Salinity in Keriya Oasis, Northwestern China, Based on the Optical-Radar Feature-Space Model

Abstract

Soil salinity has been a major factor affecting agricultural production in the Keriya Oasis. It has a destructive effect on soil fertility and could destroy the soil structure of local land. Therefore, the timely monitoring of salt-affected areas is crucial to prevent land degradation and sustainable soil management. In this study, a typical salinized area in the Keriya Oasis was selected as a study area. Using Landsat 8 OLI optical data and ALOS PALSAR-2 SAR data, the optical remote sensing indexes NDVI, SAVI, NDSI, SI, were combined with the optimal radar polarized target decomposition feature component (VanZyl_vol_g) on the basis of feature space theory in order to construct an optical-radar two-dimensional feature space. The optical-radar salinity detection index (ORSDI) model was constructed to inverse the distribution of soil salinity in Keriya Oasis. The prediction ability of the ORSDI model was validated by a test on 40 measured salinity values. The test results show that the ORSDI model is highly correlated with soil surface salinity. The index ORSDI3 (R2 = 0.656) shows the highest correlation, and it is followed by indexes ORSDI1 (R2 = 0.642), ORSDI4 (R2 = 0.628), and ORSDI2 (R2 = 0.631). The results demonstrated the potential of the ORSDI model in the inversion of soil salinization in arid and semi-arid areas.

Soil Salinity Estimation for South Kazakhstan Based on SAR Sentinel-1 and Landsat-8,9 OLI Data with Machine Learning Models

“…The sites of soil sample collection are marked on the map (1) by green rectangles. The right part (3) shows the model of predicted salinity levels obtained using Landsat 8, 9 images from 1, 9, 10, 17 and 26 April 2022 (from top to bottom). Green areas correspond to the minimum level of salinity, and lighter areas, going to yellow and red, to a high level of salinity.…”

“…Study [6] also uses Sentinel-1 SAR data and Sentinel-2 multispectral data to calculate the normalized differential salinity index (NDSI). The optical indices NDVI, SAVI, NDSI, SI based on Landsat 8 data and ALOS PALSAR-2 SAR data were used to form several combined optical radar indices (ORSDI) [3].…”

“…Nearly 20% of all irrigated land is saline, and this proportion tends to increase despite significant land reclamation efforts. It is assumed that, by 2050, the salinity of arable land in the world may exceed 50% [3].…”

Monitoring Soil Salinity Using Machine Learning and the Polarimetric Scattering Features of PALSAR-2 Data

“…This oasis is situated north of the Kunlun Mountains and south of the Taklimakan Desert, so that the southern part of the Keriya Oasis stands at higher elevations than the north part [33]. The location has a warm temperate continental climate and an average yearly temperature of 11.6 • C, while the differences in temperature between day and night are intense [34]. Similarly, the average annual rainfall ranges from 10 to 50 mm, and evaporation is as high as 2430 mm.…”