Study of an on-line measurement method for the salt parameters of soda-saline soils based on the texture features of cracks

Jianhua Ren ^a,b, Xiaojie Li ^a,c, Kai Zhao ^a,c, Bolin Fu ^a,d, Tao Jiang ^a,c
a Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
b Harbin Normal University, Harbin 150025, China
c Changchun Jingyuetan Remote Sensing Experiment Station, Chinese Academy of Sciences, Changchun 130102, China
d University of Chinese Academy of Sciences, Beijing 100049, China

Abstract: The Songnen plain in China has a typical soda-saline soil that frequently shrinks and cracks under naturalconditions during water evaporation. Contrast (CON) is a typical gray level co-occurrence matrix (GLCM) texturefeature, which can well represent the cracking degree of dried soil surface and is highly related with the saltcontent of soda-saline soils. In order to make a quantitative analysis of the effects of salt content on the crackingbehavior of soda-saline soils, laboratory controlled and field verification experiments on the soda-saline soil ofthe Songnen plain were conducted in the present study. The laboratory experiment included 56 samples andwas conducted to establish the relationships between the CON values of laboratory-generated crack patternsof soil samples and some primary salt parameters, such as the electrical conductivity (EC), Na⁺ content, Cl⁻ content, CO₃ ²⁻ content, HCO^{3 −} content and total salinity. The field verification experiment included 48 samples andwas conducted to establish the relationships between the CON values of field-generated crack patterns of soilsamples and the salt parameters. For both laboratory experimental samples and field samples, the CON valueswere computed from the binary images of the cracked patterns and were significantly linearly correlated tothe EC, Na⁺ content and salinity (coefficient of determination [R2] N0.87); the relationship between the CONvalues of soil samples and the Cl⁻ content was also quite linear (R2 N0.73). An online measurement methodfor rapid and accurate determination of salt contents of soda-saline soils was then proposed based on the resultsof the laboratory experiment. After that, the salt parameters of 48 field samples were estimated using the onlinemethod and fitted against the actual measured values. The fitting results relating the CON values and Na⁺content, Cl⁻ content, EC and salinity showed high prediction accuracy (R2 N0.91, RPD N4.49); the measurementmethod for CO₃²⁻ content also had reasonable prediction accuracy (R2 = 0.86 and RPD = 2.42) but withrelatively poor stability and poor reliability. However, the measurement method for HCO^{3 −} content showedvery poor prediction accuracy (R2 = 0.51 and RPD = 1.31).
Keywords:Soilsalinization; Soda-salinesoil; Soil cracking; Gray level; co-occurrence matrix (GLCM); Texture feature