Prof.Dr. Akram A. Al-Hadethi

Soil and water resources

Soils that contain concentrations of dissolved salts in a quantity that leads to damage to the growth of crops, and may be known as the soils in which the electrical conductivity (EC) of the saturated soil paste extract exceeds 4 dSm^-1. Such soils are formed in arid and semi-arid regions where the annual rainfall is less than 100-150 mm. Salinity is one of the main factors that stand in the way of any agricultural development, due to the negative impact of soil salinity on the production of most crops, and it also affects the chemical and physical properties of soil. The area of ??soil affected by salinity varies from one country to another, as the proportion of salinized soils in the world is about 7%, and in Iraq, it exceeds 50% of the area of ??arable lands. Increasing evapotranspiration under drought conditions is a major factor in the accumulation of salts in the soil, thus, the so-called salt-affected soils. The concentration of salts in the soil solution may increase, and in this case, it is called saline soil, while the soil solution contains an increase in salts in addition to an increase in the exchanged sodium, the soil is called alkaline or sodic soil. The dissolved salts usually consist of sodium, calcium, magnesium, chlorides, and sulfates mainly and potassium, bicarbonate, nitrates, and boron in a secondary way. The harmful effect of the accumulation of dissolved salts on plant growth is due to the overall effect of the concentration of salts in the soil solution, and this leads to an increase in its osmotic pressure and thus the movement of water to the plant may be absent, or through the specific effect of salts, which is the effect of a certain type of salts in the plant. Whether at a high or low concentration, for example, the effect of boron on plant growth is considered qualitative, as it affects the growth of many plants if its concentration exceeds one part per million in the soil solution, as well as an increase in the concentration of sodium, leads to damage to the plant. Although the weathering of primary minerals is considered the main source of salts in the soil, salinity arises as a result of the movement of salts by water from one place to another and then a collection of them as a result of certain environmental conditions. We can determine the sources of salts in the soil by weathering the minerals that make up the parent material, which helps the accumulation of salts in such lands. The increase in temperature leads to an increase in salinization, and soil salinization is closely related to temperature, and this effect appears in many soils as a result of the high temperature in Iraq, where what is known as secondary salinization is formed, especially since the amounts of rain are few. In general, the higher the temperature, the more capillary activity, i.e. the rise in groundwater through the soil volume, and salinity, in this case, is called secondary salinization. Usually, poor irrigation and the use of water with a high concentration of salts leads to the formation of secondary salinity, and for cultivation, these salts must be disposed of by washing with non-salt water to reach a concentration of salts less than 4 dSm-1. Conventional salinity treatment methods such as salt scrubbing, surface skimming, and water scrubbing do not work; This is due to the large area of the saline soils, as well as the high treatment cost, time, and effort, and the use of large quantities of water. It also needs to establish efficient drainage networks. Recently, many salinity treatment compounds have appeared, including chemical and organic. It has multiple brand names, and the competition for it has become great among the manufacturers due to its positive effect in reducing the effect of salts in the soil, improving the chemical properties of the soil, and reducing the percentage of adsorbed sodium. Recent studies have resorted to the use of some chemical and organic compounds to study their effect in reducing salts from soil slag by a chemical process such as ion exchange (displacement), Among these compounds are phosphogypsum and humic acids. It was used by adding them directly to the soil and it gave good results by reducing the salinity and sodium adsorption ratio of saline-sodic soils.