Dependence of saline soils reaction (pH) on some physico-chemical characteristics of soil

Analysing the multiple regression equations pH=f (SAR, ECe % clay) obtained by analytical data concerning the saline soils of the Middle basin of Euphrates, the following conclusions resulted. In case of soils without gypsum one established that pH is highly dependent on ECe and SAR variations and this dependence increase with salinization. In case of soils with gypsum, the variation of pH is much slowly influenced by considered variables. The influence of clay content appear evident only in case of saturation paste pH variation; generally, the influence of all considered variables is more intensely expressed in saturation paste pH variation, than watery suspension 1 : 2.5 pH variation. The calculated equations indicate that in case of gypsum soils, the desalinisation of soil took place with its whole desalkalization and certainly without alkalinization. In case of soils without gypsum, the soil desalinization took place without the whole soil desalkalisation and with a soil alkalinization. Using the method of groups for the comparison of two arithmetical means one established that watery suspension 1 : 2.5 pH values and the SAR values can be used as quantitative differentiating indexes within the two groups of soils (soils with gypsum and soils without gypsum) between consecutive salinization degrees (except the pH values of soil with gypsum having salinization less than 16 mmhos/cm and the SAR values of soils without gypsum having salinization less than 8 mmhos/cm) and also for the same salinity between the two groups of soil (soils with and without gypsum). For all the salinization degrees (ECXe , 4, 4-8, 8-16, 16-32) watery suspension 1:2.5 pH values and the SAR values of the soils without gypsum are significantly higher than those of the soils without gypsum, proving that alkalization and alkalinization processes are significantly different in these two groups of soils.