The effect of gypsum on soil texture class in gypsic soils using leaching and Hess methods

Since gypsum affects on the soil physical¡ chemical and biological properties¡ so the presence of gypsum on soil behavior¡ including soil texture¡ is important. The aim of this study was to compare methods of soil texture determination; touching (field)¡ leaching¡ Hydromer and Hess¡ in the soils of Khoda afarin plain¡ Ardebil province¡ with an area about 21000 ha. For this purpose¡ soil samples collected from 20 soil profiles¡ with three replications and a factorial experiment was conducted in a completely randomized design. The results showed that although the two methods of soil texture determination (leaching and Hess) had similar soil texture classes¡ but in the touching method¡ because large crystals of gypsum (sand sizes)¡ soil texture may be estimated more coarse. Also¡ Hydromer method resulted an error in measuring of soil texture¡ because the flocculation of fine particles. In the measuring by pre-treatment of BaCl2¡ the success of accurate estimation of soil texture depends on gypsum percent and particle size distribution of gypsum crystals. In the gypsum complete leaching method¡ soil texture class was usually heavier than other methods¡ so that¡ the variance analysis table showed that the effects of leaching and particles BaCl2 coating¡ on the soil particles percentage has been significant at 1% level. So¡ removing of gypsum in the precise measurement of soil texture is not correct¡ because gypsum constitute a major component of the solid material and remove it from the gypsic soils does not have a scientific justification and basis.