Remote Sensing of Soil Alkalinity and Salinity in the Wuyu’er-Shuangyang River Basin, Northeast China

Abstract

Abstract:The Songnen Plain of the Northeast China is one of the three largest soda saline-alkali regions worldwide. To better understand soil alkalinization and salinization in this important agricultural region, it is vital to explore the distribution and variation of soil alkalinity and salinity in space and time. This study examined soil properties and identified the variables to extract soil alkalinity and salinity via physico-chemical, statistical, spectral, and image analysis. The physico-chemical and statistical results suggested that alkaline soils, coming from the main solute Na 2 CO 3 and NaHCO 3 in parent rocks, characterized the study area. The pH and electric conductivity (EC ) were correlated with both narrow band and broad band reflectance. For soil pH, the sensitive bands were in short wavelength (VIS) and the band with the highest correlation was 475 nm (r = 0.84). For soil EC, the sensitive bands were also in VIS and the band with the highest correlation was 354 nm (r = 0.84). With the stepwise regression, it was found that the pH was sensitive to reflectance of OLI band 2 and band 6, while the EC was only sensitive to band 1. The R 2 Adj (0.73 and 0.72) and root mean square error (RMSE) (0.98 and 1.07 dS/m) indicated that, the two stepwise regression models could estimate soil alkalinity and salinity with a considerable accuracy. Spatial distributions of soil alkalinity and salinity were mapped from the OLI image with the RMSE of 1.01 and 0.64 dS/m, respectively. Soil alkalinity was related to salinity but most soils in the study area were non-saline soils. The area of alkaline soils was 44.46% of the basin. Highly alkaline soils were close to the Zhalong wetland and downstream of rivers, which could become a severe concern for crop productivity in this area.

Geoinformatics for Quantifying Salt Affected Soils in Gohana, Haryana Using Soil Techniques

“…There is a positive and significant correlation between pH and EC (r = 0.57; p≤0.01) pH and Na + (r =0.59; p≤0.01) and Cl − (r =0.63) and SO 4 2− (r = 0.51) signifying that the pH of the soil is primarily influenced by the Cl − and SO 4 2− content (Table 2). Bai et al, (2016) also reported positive correlation between pH and EC and Na + ions in the Wuyu'er-Shuangyang River Basin, Northeast China. The pH variation in the area is small as indicated by low CV which can be attributed to high buffering capacity of the soils and absence of carbonates in the saturation extract (Sharma and Gupta, 1986).…”

“…Vadivelu et al, (2001) also reported positive significant correlation between available K and organic carbon and clay. Under saline and sodic soils, K fertilization management may need to be altered because of potassium competition with other cations especially Na + in the plant and to the effects of salinity in K reactions in soil (Bar-Tal et al, 1991). The coefficient of variation varied sharply with depth indicating lateral and vertical variation.…”

Temporal Interpolation of Satellite-Derived Leaf Area Index Time Series by Introducing Spatial-Temporal Constraints for Heterogeneous Grasslands

“…Due to the human activities, climate, geology, and terrain conditions, these mid-latitude semi-arid grasslands are salinized and alkalized at various degrees [32][33][34]. As a result, the Songnen grasslands are at different succession stages with diverse community compositions and, hence, show a typically heterogeneous landscape.…”

Agricultural Soil Alkalinity and Salinity Modeling in the Cropping Season in a Spectral Endmember Space of TM in Temperate Drylands, Minqin, China

“…There is renewed interest in the use of broadband multispectral imagery for regional soil salt content prediction (e.g., [4,5,[9][10][11][12][13][14][15][16]). Generally, these studies include (1) the bands' selection and investigation of spectral indices, including salinity indices and vegetation indices (e.g., [12,13]); (2) the optimized combination of bands and spectral indices for modeling, such as [4,5,14]; and (3) the long-term soil salinity dynamic analysis, such as in References [15,16].…”