The publication of this Handbook was supported by the Russian Federation

Table А.8. Parameters and criteria of gypsum-rich soil horizons [16]
№
Parameters
Criteria
1
The depth of  the upper 
boundary of  gypsum-rich 
horizon, cm
Gypsum accumulation at/near the surface (the upper boundary within 0-20 cm)
Gypsum accumulation in the upper part of  soil profile (20-50 cm)
Gypsum accumulation in the middle of  soil profile (50-100 cm)
Gypsum accumulation in the lower part of  soil profile (100-200 cm)
Gypsum-containing bedrock (deeper than 200 cm)
2
The content of  gypsum 
(CaSO
4
x2H
2
O),%
Low (2-10%)
Medium (10-20%)
High (20-40%)
Very high (more than 40%)
3
The thickness of  gypsum-rich 
horizon, cm
Thin <30
Medium 30-100
Thick >100 
4
Prevailing sizes of  gypsum 
pedofeatures, mm
Flour- or powder-sized (very fine crystalline) <0,1
Fine crystalline 0,1-1,0
Medium crystalline 1-5
Coarse crystalline >5
5
The morphology of  gypsum 
pedofeatures
Flour-like or powdery gypsum (forming a continuous gypsum-rich horizon that also contains 
calcium carbonate and soluble salts)
Small gypsum concretions (so-called 'millet-like' or 'rice-like' concretions crushed between fingers 
and thumb)
Accumulations of  fine-crystalline gypsum ('worm-like' features along pores and root channels that 
cause a significant increase in the soil horizon density)
'Pseudosand' of  sand-like medium-sized gypsum crystals
Columnar (spongy) fine-crystalline gypsum
Gypsum roses and plates of  transparent yellowish glass-like gypsum
А4. Criteria for estimating the content of carbonates in soils
Description of  a saline soil necessarily requires an estimation of  the content of  carbonates, 
particularly, the upper boundary of  effervescence with 10% HCl , the properties of  the horizon 
of  maximal carbonate accumulation, etc. Judging from the upper boundary of  effervescence, soils 
can be subdivided into the following grades: calcareous at the top (with the upper boundary of  
effervescence at 0-20 cm), calcareous in the upper part of  profile (20-40 cm), calcareous in the 
middle part of  profile (40-100 cm) and calcareous in the lower part of  profile (100-200 cm). An 
estimation of  the content of  carbonates in soils according to the Classification and Diagnostics of  
Soils of  the USSR ( 1977) is based on the presence of  highly calcareous (more than 30% CaCO
3
) 
horizons within the soil profile and bedrock [11]. Soil grouping by the content of  CaCO
3
 within a 
calcareous layer as well as by the depth, thickness and consistency of  highly calcareous ( more than 
30% CaCO
3
) layers is presented in the Tables A.9 - A.10.