UDC 631.4

Prokopyeva K.O., Konyushkova M.V. HARMONIZATION OF THE RESULTS OF SOIL SALINITY CHEMICAL STUDY // Arid Ecosystems. 2023. Vol. 29. № 3 (96). P. 24-35. | PDF

Soil salinity is one of the main ecological factors that limits the growth and productivity of many plants. Its assessment in different countries is carried out by different methods. In Russia and some other countries, soil salinity is assessed using water extracts. Internationally, the method of electric conductivity of soil paste extracts is widely used. These methods are labor-consuming, and, therefore, the reduced methods are used to assess soil salinity for mass analysis. Thus, in Russia, salt surveys are often evaluated by the leading toxic ion (chlorine or sodium). In a number of foreign countries assessment is given by electrical conductivity at various ratios of soil to water (1: 1; 1: 2.5; 1: 5; 1: 10). In this study, comparisons of different methods for substantiation of possibility to use electrical conductivity measurement in 1: 5 suspension were carried out. The following methods were compared: 1 – method of determination of specific electric conductivity in water suspension (1: 5); 2 – method of determination of pNa and pCl measured in water suspension (1: 5) using ion-selective electrodes; 3 – determination of sodium in water suspension (1: 5) by atomic absorption spectrometry. Salinity was evaluated in samples of light clayey soils of the dry steppe zone of mainly chloride-sodium salinity type. The results showed that when determining the activity of ions, the greatest correlation was observed between measurements of specific conductivity (conductometer) and sodium activity (ion-selective electrodes). A sufficiently close correlation between specific conductivity and the content of sodium ions in the water extract was revealed and the function of recalculation of these indicators was obtained: ЕС_1: 5 = 0.213Na_1: 5 + 0.17 (with intercept); ЕС_1: 5 = 0.23Na_1: 5 (without intercept). For evaluation of salinity degree according to specific conductivity index (1: 5) the following criteria are suggested: 0-0.4 dS/m (non-saline), 0.4-0.6 dS/m (slightly saline), 0.6-1 dS/m (medium saline), 1-1.9 dS/m (strongly saline), > 1.9 dS/m (very strongly saline). When comparing different gradations of soil salinity with the help of contingency tables using chi-square and kappa index, the presence of statistically significant contingency was revealed, which allows us to use different methods of soil analysis to assess the degree of salinity.

Keywords: salinity, soil analysis, electrical conductivity, ion selective electrodes (ISE), sodium, Caspian Lowland.

Financing. The work was supported by the funds for the Eurasian Center for Food Security of Lomonosov Moscow State University (Decree No. 1736-r, dated 26/06/2021).

DOI: 10.24412/1993-3916-2023-3-24-35

EDN: WCVAFO