Marc Schober is the editor of Farmland Forecast an educational blog devoted to investments in agriculture and farmland.
Irrigation Uses in Farming
Jan 12, 2010
In order for plants to survive, they need sun and water. Unfortunately sun will deplete readily available water for plants in arid or semi-arid climates. Water provides nutrients to a plant so it can grow and carry out its functions. If a plant does not have enough water, it will die. Conversely, too much water will wash nutrients out of the soil and away from a plant.
To assist crops in dry areas and during periods of inadequate rainfall, irrigation is used as an artificial application of water to the soil. Irrigation also protects plants against frost, suppresses weed growing in grain fields, and helps in prevent soil consolidation. In contrast, agriculture that relies only on direct rainfall is referred to as rain-fed farming.
In the United States, irrigation withdrawals accounted for 40% of total freshwater withdrawals in 2000, according to the United States Geological Survey (USGS). Only 16% of all harvested cropland is irrigated in the U.S., but irrigated land generates almost half of the value of all crops sold because fruits and vegetables often require more water than is available and need to be irrigated, compared to grains.
Spray irrigation is a common type of irrigation in the U.S. Most spray irrigation systems are on a center pivot system where a quarter mile of piping pivots around a center point water source. The irrigation system sprays water over and out to crops while it rotates. Row crops like corn and soybeans are the most common crops to use pressurized spray irrigation.
Spray irrigation wastes water because a great deal of water will evaporate before it gets absorbed by the crops. In addition, spray irrigation systems typically cover 128 to 132 acres in a 160 acre, quarter section, leaving an average of 30 acres not irrigated, according to the USGS. More efficient spray irrigation systems are being built. These systems feature a more gentle flow of water so it will not evaporate as quickly.
Flood irrigation is when cropland is purposely flooded so all of the exposed soil will absorb water. Water will be pumped on to fields and plants will soak up as much as possible before the water evaporates. This method of irrigation wastes a lot of water by pumping it all over a field. Runoff can be collected, but not all wasted water can be collected, and only about half of the water reaches the root zones of the plants, according to the USGS.
Flood irrigation is more popular among developing countries where other irrigation systems have high startup costs, or are unavailable. Rice and wheat crops are the most common crops to be flood or drainage irrigated.
Drip irrigation is becoming the irrigation of the future. As other irrigation systems tend to waste water by applying too much, or water is evaporated before the plant uses it, drip irrigation systems apply water directly to the root zone of a plant.
In a field, perforated hoses are laid out like a grid so they run along the base of a plant, or just below the surface next to the base of a plant. Water is then pumped through the hoses slowly so the water trickles out and can be efficiently absorbed by the plant. Minimal water is lost due to early evaporation.
Drip irrigation systems are typically used in fields that grow rows of fruits or vegetables. Tomatoes are a common drip irrigated crop because they demand such high amounts of water.
Here are some benefits of drip/microirrigation systems according to Colorado State University Cooperative Extension:
· Microirrigation is a low pressure, low volume irrigation system suitable for high-return value Crops such as fruit and vegetable Crops.
· If managed properly, microirrigation can increase yields and decrease water, fertilizer and labor requirements.
· Microirrigation applies the water only to the plant's root zone and saves water because of the high application efficiency and high water distribution uniformity.
· Microirrigation can irrigate sloping or irregularly-shaped land areas that cannot be flood irrigated.
· Any water-soluble fertilizer may be injected through a microirrigation system.
Irrigation can be quite costly. The total cost of irrigating includes diesel fuel, labor, maintenance, and ownership costs. A center pivot irrigation system will cost up to $116.45 per acre, according to University of Arkansas. The purchase price for a new center pivot system that includes a standard well, pump and gearhead, power unit and center pivot can total about $75,000. Flood irrigation with a standard well can run between $59.16 and $97.29.
Irrigation use accounts for 60% of all freshwater that is withdrawn in the world. Water is not only used on farm fields, but on lawns as well. In the U.S., up to 1.5 billion gallons of water a day are used for landscaping purposes, according to the Environmental Protection Agency. As freshwater becomes scarcer, irrigation systems will be evaluated and altered to use less water.
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