An increase in salt content, usually of agricultural soils, irrigation water, or drinking water is called salinization. Salinization is a problem because most food crops, like the human body, require fresh (nonsaline) water to survive. Although a variety of natural processes and human activities serve to raise the salt contents of soil and water, irrigation is the most widespread cause of salinization. Almost any natural water source carries some salts; with repeated applications these salts accumulate in the soil of irrigated fields. In arid regions, streams, lakes, and even aquifers can have high salt concentrations. Farmers forced to use such saline water sources for irrigation further jeopardize the fertility of their fields. In coastal areas, field salinization also results when seawater floods or seeps into crop lands. This occurs when falling water tables allow sea water to seep inland under ground, or where aquifer subsidence causes land to...