Salt affected soils are simply defined as soils that have been adversely modified for the growth of most plants by the presence of soluble salts, exchangeable sodium or both. Although this brief description of salt affected soils gives the impression that they have serious limitations for agriculture production, yet generally these they soils are potentially productive. They cannot be brought under the plough until suitable technology for their amelioration and management is evolved. However, the economic implications involved in reclaiming salt affected soils are the major consideration to increasing production.

Salt affected soils are widely spread in semi-arid and arid areas such as Egypt. The provision of irrigation water is one of the most important factors for the expansion of agriculture in the direction of intensification as well as of expanusion of cultivated land. The success of any agriculture development in Egypt depends entirely on the wise use of the available water resources.

It is a fact that saline soils distribution is closely related to environmental factors such as climate, geology, geochemical and hydrological conditions. The formation of the different types of salt affected soils in the irrigated area is largely related to the degree of concentrations of chlorides, sulphates, and bicarbonates which dominate following the same order - saline, saline - alkali, gypsum veined and alkali soils are formed respectively.

Nature and Formation of Salt Affected Soils

The majority of salt-affected soils are located in the northern Central part of the Nile Delta and on its eastern and western sides. Other areas are found in Wadi El- Natroun, Tal El- Kebeir, the Oases, as well as in many parts of the Nile Delta and Valley and El- Fayoum province.

Sodium chloride is the dominant salt and it is the main source of salinization. Inundating the soils with sea and with sea and lake salty water for a long time is the most important factor for salinization in the mentioned soils, besides the tidal effect and the salty soil solution. Shalma and El-Hamoul South Burullus lake represent this type. Magnesium chloride and magnesium sulphate are the dominant salts and main source of salinity in the Manzala Lake area, while sodium chloride is the dominant salt representing the main source of salinization in the area of Abees South Mariut Lake.

Sodium chloride and sodium sulphate are the dominant salts Mariut and Tal-El- Kabeer areas respectively. The main factor responsible for the deterioration of these soils is seepage from irrigation canals in Mariut and from Ismailia canals in Tal El-Kebier. Sodium carbonate and sulphate are the dominant salts in Ferhash area. The main factor for alkalinization is the effect of biological sulphate reduction. Sodium chloride is the dominant salt and sodium saline irrigation water (5000 ppm) is the main factor for salinity formation in this area.

Alkali soils are characterized by their adverse physical properties, their dispersed condition and impermeability to water which are to be directly connected with sodium as the dominant exchangeable  base and the presence of magnesium silicate precipitated during the process of soil alkalinization. The gypsum-veined soils are characterized by their low permeability to water the presence of Mg, Ca, and Na salts in varying amounts.
In addition, the presence of an impermeable layer underlain by a horizon veined with gypsum at variable depths is always present. On wetting the impermeable layer in such soils becomes highly dispersed, while it becomes hard when dry.

Such deteriorated soils are connected with a number of factors:- depth, duration, regularity and fluctuation of groundwater. The gypsum- veined type is found under conditions of deep water tables, whereas the alkali type is found on low- lying areas where the water table is high.

The cropping pattern in Egypt is somewhat adjusted to soil condition. In the northern part of the Nile Delta where soil salinity is somewhat high, crop rotation includes rice and cotton as the main summer crops and wheat and clover as the main winter crops. All of these crops have proved to be salt - tolerant or semi - tolerant. Sugarbeet which is known to be tolerant to salinity has been grown in the Northern Delta and is now supporting a large sugar factory. Further expansion in sugarbeet production is planned in the new reclaimed land west of the Delta.

Nowadays, the government activities for reclaiming salt-affected soils and improving soil productivity are concentrated through three main programmes aimed at increasing soil productivity and treating the hazardous effects of salinity and alkalinity. The first programme is to introduce drainage systems covering all cultivated areas in Egypt. The overall objective is to cover 6.4 million feddans with till drainage before the year 2000. The second is the  reclamation programme of salt affected soils. The third is soil improvement which is one of the main activities of the Executive Authority for land Improvement Projects, the Ministry of Agriculture and land reclamation.

Reclamation of salt affected soils in Egypt

1. Reclamation of virgin salt affected soils with high saline water table, i.e. lake bed soils in northern Egypt.
2. Reclamation of virgin saline or potentially saline soils with relatively deep water table, e.g. desert areas and oases.
3. Reclamation of waterlogged soils, northern delta areas. 
4. Use of chemical amendments such as:-

1. Soluble Ca salts, e.g. gypsum and calcium chloride.
2. Acid or acid forming substances, e.g. sulphuric acid, iron sulphate, aluminium sulphate, lime sulphur, sulphur, pyrite.
3. Calcium salts of low solubility, e.g. ground lime stone.