Topics: Agriculture, Irrigation, Soil Pages: 4 (993 words) Published: November 30, 2010
Problems arise in the world due to salinity, as when the salt gets on to the top of the causes disaster to the plants and trees. Salt comes in many forms in the natural environment—calcium, magnesium, carbonate, sodium chloride, bicarbonate, and sulphate. Many landscapes are naturally saline, but secondary salinity isn’t so natural, occurring when salts from deep within the earth are dissolved and deposited into soil and water as a result of human activity. This can happen in one of two ways: Dryland salinity - from removal of deep-rooted plants

In dry regions, deeply-rooted perennial plants, such as shrubs, trees, and grasses, play an important role in regulating groundwater levels. As water is applied to the soil, the plants drink it up and breath it out through a process called evapotranspiration. This ensures that the water table levels stay relatively stable.

But this balance is thrown into chaos when farmers clear the land to gain more space for grazing animals and cultivating food crops. In doing so, they remove the deep-rooted plants and replace them with shallow-rooted annual crops. These plants do not take up as much water as once-plentiful native plants, and as a result, more water remains in the soil.

Over time—up to 30 years—water accumulates in the land, causing the water table to rise. As it does so, it passes through layers of salt and dissolving the deposits that have existed in the land for centuries. The shallow-rooted plants can’t keep up with the rising water levels, which results in rising salt deposits in ever-increasing concentrations in topsoil. Irrigation salinity - from overirrigation

Much like dryland salinity, irrigation salinity results in a rising water table that brings deep deposits of salt upwards through soil layers. But instead of being caused by land clearing, it results from increased irrigation. As water soaks...
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