Irrigation

Irrigation is the process of supplying water to crops by artificial means. Each farming region’s terrain, precipitation, soil drainage, and type of crops determine the amount of water a farming operation needs. Irrigation worldwide has increased as the population has grown and as desertification has taken over previously healthy cropland. The FAO has stated that from 1950 to today, a period in which the world population went from 2.5 billion to 6.5 billion people, irrigated area doubled and water withdrawals tripled. Though irrigation helps agriculture meet the increasing demand for food, it also contributes to desertification if not done the correct way.

Farmers in arid and semiarid regions obtain irrigation water from surfaces waters, such as lakes, rivers, and ponds. This water must usually be carried long distances from its source to the fields. Underground water supplements surface waters, and in some instances it serves as the sole water supply. If irrigation draws water out of the ground quicker than nature replaces it, an overdraft occurs. In an overdraft the land above the aquifer may sink. In Europe water officials have used this process to their advantage. Workers drill deep wells alongside rivers, and the wells draw water from saturated soils close to the riverbank. Soil and gravel partially clean the water as it filters through on the way from the river to the well. Only very severe droughts interfere with this method of water purification. More about this topic is found in the “Drought” sidebar.

Irrigation of severely dry land must include precautions so that water does not simply rush over the ground’s surface and take soil but never reach the crops’ roots. Irrigation water may be supplied by the following systems: sprinkler systems; field-flooding; filling furrows between crop rows with water; subirrigation (in which water from ditches or porous vessels percolates into the soil); or drip irrigation. Drip irrigation offers the most efficient water delivery approach, especially in water-precious dry parts of the world. Drip irrigation periodically delivers small amounts of water to the soil above root systems through small tubes. Drip irrigation provides the three following advantages: (1) reduced total water requirements; (2) slow release that prevents large losses by evaporation; and (3) adaptation to hilly or flat terrain.

Improper irrigation causes unneeded damage to lands already threatened by desertification. First, repeated irrigation that does not allow the soil to absorb the water can cause salinization as salts slowly accumulate in the soil. Salinization, as mentioned earlier, further reduces the soil’s quality and leads to more desertification. Farmers who try to remove salinization with water may create a second problem from irrigation—waterlogged soil.

Waterlogged soil eventually raises the water table and kills plant roots. At the same time, soil microbes cannot carry out their normal metabolism so they do not degrade organic matter. Both salinization and waterlogging have become serious problems in parts of the world suffering desertification.

Source of Information : Green Technology Conservation Protecting Our Plant Resources