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Soil salinity manаgement manual | Part I.Soil salinity management in the Eurasian Region
of irrigation waters and irrigated soils are aimed to improve their quality and increase yields of
agricultural crops. This type of amelioration is usually performed by applying chemical substances
to water or soil.
The chemical amelioration treatments include the following:
• Physicochemical methods for the improvement of medium-quality irrigation waters (Class 2,
according to the state standard, DSTU 2730: 2015). Firstly, this involves water treatment with
calcium ameliorators (gypsum, chalk, lime,
calcium nitrate, calcium chloride and calcium-
containing waste products such as phosphogypsum);
• The application of the above-listed substances as well as sediments (loesses, red-brown clays,
etc.) to soils in a dry state is economical (as there is no need for water or water-amelioration
equipment).
The mechanism of action of ameliorators involves the displacement (or prevention of adsorption)
of salinity-forming cations (primarily sodium) within the soil exchange complex. It is accompanied
by favourable changes in hydrophysical, agrochemical, physicochemical, biological and
other soil
properties due to a decrease in the mobility of soil colloids, lowering of soil alkalinity, improvement
of micro- and macrostructure, increase in the water resistance of soil aggregates and also an increase
in
soil permeability, which prevents compaction, surface crust formation, loss of structure and
swelling phenomena. This is also accompanied by an increase in levels of availability of nitrogen,
phosphorus, potassium and calcium, a decrease in solubility and mobility of humus,
activation of
microbiological processes and a general increase in agricultural crop productivity [7].
The chemical amelioration of irrigated soils in Ukraine should be conducted under the following
conditions:
• the use of medium-quality irrigation waters (Class 2, according to the state standard, DSTU
2730: 2015) with moderate risks of occurrence of irrigation-induced salinity or alkalinity in
soils;
• the application of soil leaching to remove salts with irrigation waters of different qualities
and the use of formerly irrigated soils with primary and secondary salinity or alkalinity and
decalcination;
• giving amelioration priority to soils that have high and moderate alkalinity;
• the application of ameliorators to soils in the form of solution or suspension and along the
contours of Solonetz areas during the periods of maximal manifestation of agrophysical
alkalinity;
• the use of local ameliorators
containing calcium, iron-calcium and sulphuric acid components
of industrial waste under a condition of their compliance with sanitary and ecological
regulations (toxic substances originated from waste application should not accumulate in soil
and groundwater in quantities above maximal permissible levels);
• the use of ameliorated lands for growing water-demanding, highly productive and valuable
crops in preference to salt-resistant and
alkali-resistant crops species, varieties and hybrids.
To save resources, the chemical amelioration of irrigation water should be conducted only when
the agrophysical alkalinity of soils and the toxic impact of soil solution on plants reach critical
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Chapter 4.The rational use of saline and alkaline soils (with examples from Ukraine)
levels, i.e., with early spring irrigation prior to sowing and during the germination of agricultural
crops and in autumn during recharge irrigation.
Irrigation-induced alkalinization of soils can be mitigated by applying dry chemical ameliorators
directly to soil. The ameliorators should be applied during post-harvest
ploughing and harrowing
of soils in autumn to prepare the soil for sawing in spring. If a soil has not undergone autumn
tillage, then ameliorators can be applied to the soil just before or just after spring ploughing. Under
winter crops and perennial grasses, the optimal time for ameliorator application is during the late
winter or early spring (February-March), when the soil surface is partly frozen.
It is also possible to use local limestone and wastes of stone mining and sugar industries. Such
ameliorators contain calcium in the form of carbonate, CaCO
3
,
which has a gentle, but long-
lasting ameliorative effect (compared to that of phosphogypsum) and, therefore, should be applied
to soil with some surplus so that it lasts for several years.
In some industrial areas, it can be economically feasible to use iron-calcium wastes of the steel
industry as soil ameliorators. Calcium carbonate wastes with permissible levels of toxic substances
can be applied to soils with irrigation waters in the form of suspensions or after their chemical
treatment with sulphuric acid [7].
