Biosalinity

Many arid and semi-arid areas actually do have sources of water, but the available water is usually brackish (500-5000 ppm salt by weight) or saline (3-5% salt). The water may be present in underground aquifers or as seawater along coastal deserts. With traditional farming practices, saline water results in soil salinization, rendering it unfit for raising most crop plants. Indeed, many arid and semi-arid areas were simply considered unsuitable for agriculture, and agricultural development of these areas was not systematically attempted until the second half of the 20th century.

Research in biosalinity includes studies of the biochemical and physiological mechanisms of salt tolerance in plants, breeding and selection for salt tolerance (halotolerance), discovery of periods in a crop plant's life cycle when it may be less sensitive to salt, use of saline irrigation water to increase desirable traits (such as sugar concentration in a fruit) or to control the ripening process, study of the interaction between salinity and soil properties, and development of naturally salt-tolerant plant species (halophytes) into useful agricultural crops. See also halophile bacteria, which thrive under conditions of high salinity.

When properly applied (watering well in excess of evapotranspiration, maintaining soil structure for excellent drainage), brackish-water irrigation does not result in increased salinization of the soil. Sometimes this means that farmers have to add extra water after a rainstorm, to carry salts back down to below the root zone.