Soil alkalinity refers to a condition in which the soil has a high concentration of alkaline substances and a high soil pH, generally above 8.5. It is an important environmental and agricultural problem because it changes the chemical and physical properties of soil and reduces its capacity to support healthy plant growth. Alkaline soils are commonly associated with the accumulation of sodium carbonate, sodium bicarbonate and other basic salts. The development of soil alkalinity is influenced by natural environmental conditions as well as human activities, particularly improper irrigation and drainage practices. One of the major reasons for soil alkalinity is the accumulation of soluble salts and exchangeable sodium in the soil. In regions with low rainfall and high evaporation, water containing dissolved salts moves upward through the soil by capillary action. As the water evaporates from the surface, salts remain behind and gradually accumulate. Repeated evaporation without sufficient rainfall or drainage can therefore increase the concentration of alkaline salts in the upper layers of soil. The nature of the parent material also contributes to soil alkalinity. Some rocks and minerals contain large quantities of basic compounds, carbonates and bicarbonates of calcium, magnesium and sodium. During weathering, these substances are released into the soil. Under conditions of inadequate leaching, the alkaline materials remain in the soil and gradually increase its pH. Thus, the geological composition of an area can determine its natural tendency toward alkalinity. Climate is another important factor. Soil alkalinity is