The publication of this Handbook was supported by the Russian Federation

Causes of  soil salinity
Soil salinity is multi-factorial phenomenon, i.e., caused by various factors or combinations of  
factors. Salinization is a complex process that can develop in different ways in different areas of  the 
Eurasian Region, often caused to a significant extent by the over-exploitation of  natural resources, 
in particular, unsustainable and inappropriate methods of  agriculture and land use, and incorrectly 
managed water resources, the consequences of  which become aggravated by climate change with 
extreme droughts and other challenges.
Balyuk and colleagues point out that causes of  secondary salinity of  soils in Ukraine can also include 
the following: (i) an unfavourable chemical composition of  irrigation water, with the contents of  
sodium and potassium salts in their equivalent concentrations exceeding the contents of  salts 
of  calcium, magnesium, iron and other bi- and trivalent cations; (ii) the raising of  groundwater 
towards the surface layer having an equally adverse chemical composition can cause persistent 
secondary salinization and (iii) leaching of  saline soils as well as paddy rice cultivation on naturally 
saline soils (initial years).
Research by V.A. Kovda, E.I. Pankova, I.P. Aidarov and other scientists [11, 14] showed that the relic 
and modern salinity of  soils and waters in the Central Asia are caused by the combined influence 
of  climate, topography, geomorphology, bedrock geology and history of  the development of  the 
Turan Province. The manifestations of  the salinization process are predetermined by the two types 
of  landscapes: i) landscapes with natural (relic) soil salinity and ii) landscapes with the secondary 
accumulation of  salts. Gentle slopes and an absence of  natural drainage of  the groundwater in 
combination with irrigation result in changes in the state of  soluble salts including the mobilization 
and upward migration of  ancient salt accumulations. The main causes of  secondary salinity in 
Central Asia include excessive irrigation, significant losses of  water from the channels on irrigated 
fields and imperfect drainage systems that result in a rapid rising of  the groundwater and salt 
accumulation within the root zone. The inadequate maintenance of  drainage networks triggers the 
mobilization of  salts from deep aquifers.
Bucknall et al. [19] point out that over 70% of  salts carried by trans-boundary rivers originate 

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Soil salinity manаgement manual | Part I.Soil salinity management in the Eurasian Region 
from drainage systems that discharge 10-25% of  their water back to the rivers (with the remaining 
amount used on land). Water unsuitable for agricultural use or drinking, with a salinity of  1.5-1.8 
g/l and a hardness double that of  the maximal permissible level, is still supplied to consumers 
in the lower reaches of  the Amu Darya River. The main systems of  land use in such regions are 
recognized as being at risk from the combined impact of  natural and man-made phenomena [11, 
13, 14].