The publication of this Handbook was supported by the Russian Federation

Fig. 3.1. Factors of pedogenesis (A), water-physical properties 
(B) and physiochemical properties of soils (C).
Designations: I – humid zone; II – steppe zone; III – dry steppe zone; IV – semidesert and desert zones; 
1 – value   ; 2 – litter to biomass ratio; 3 – energy of  soil formation; 4 – the content of  particles < 0,001 
mm; 5 – soil moisture; 6 – soil aeration; 7 – the content of  water-resistant peds; 8 – nutrient availability; 
9 – the ration of  humic to fulvic acids; 10 – soil exchange complex value; 11 – humus content; 12 - pH value
The inability to assess the rates of  changes in soil properties 
and fertility is a major shortcoming of  this model.
3.3. Models and methods for the assessment of moisture and salt 
regimes of irrigated lands
An assessment of  the dynamics of  moisture and salt regimes of  irrigated soils requires 
knowledge of  the quantitative relationships between water and salt transport, environmental 
conditions and land use. At the same time, the use of  complex multi-factor equations of  mass 
transfer in soils requires determinations of  numerous parameters. Therefore, the use of  simpler 
mathematical  models  based  on  most  significant  parameters  is  preferred  for  making  forecasts.  
An assessment of  the dynamics of  moisture regime of  lands with a free natural drainage and a deep 
(> 5-10 m) growndwater table can be done by the following simple method [1, 2]. A prognostic 
moisture regime of  soils is determined from a balance equation and an equation connecting 
moisture exchange processes between the root zone, atmosphere and subsoil [1].
(3.2)

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Soil salinity manаgement manual | Part I.Soil salinity management in the Eurasian Region 
(3.3)
where 
 - relative humidity of  soil in the beginning and the end of  the assessement 
period 
; m0 – porosity, % of  volume; W
0
 – maximal molecular moisture capacity, 
% of  
volume; W – soil moisture content, % of  volume;
r0 – rooting depth, mm; Δt –assessment period, days; K
B
 – 
;
g - water exchange between ; soil and lower layers, mm.
Advantages of  the suggested method of  moisture regime prognosis include the simplicity of  
calculations and the small number of  input parameters, which can be easily determined in the 
course of  soil research. Amplitude of  moisture within the root zone can be set for any species of  
agricultural and natural grassland vegetation. The value of  total evaporation can be determined 
with a good precision from the biological characteristics of  plants, air temperature and humidity 
and the total water input. In cases of  a shallow occurrence of  the groundwater table, equations 
(3.2) and (3.3) are supplemented by groundwater balance equations [1].
Mean content of  salts within the layer 0 < x ≤ L can be calculated with the use of  nomogram (Fig. 
3.2), where the solid lines correspond to desalinization process, with downward water fluxes ( 
> 0); the dotted lines correspond to salinization process, with upward water fluxes ( 
< 0); Ре - 
Peclet dimensionless number;
 
; c
0
 – initial salt content in soils,
%; c
1
 – irrigation water salinity, (c
1
 0); c – salt content in soils by the end of  the assessment period, 
%.
The salt regime of  soils with a high cation exchange capacity (more than 15-20 meq/100 g) is 
determined from the sum of  toxic salts and the concentrations of  calcium, sodium and magnesium 
in soil solution and soil exchange complex. In this case, the model should incorporate convection-
diffusion proceses and ion exchange sorption balance.

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Chapter 3.Assessing and forecasting the development of soil salinization and alkalinization processes