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50 Ways Farmers Can Protect Their Groundwater
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49. Take Precautions When Irrigating

furrow irrigation

There are several types of irrigation, and each has its own special benefits and problems when it comes to groundwater.

With furrow irrigation, water is ponded between crop rows created during planting and cultivation. With flood irrigation, water is pumped or allowed to flow into a ridged or diked area of the field. The basic risk with these systems is overapplication of water. Overapplication increases the chances that surface-applied or soil-incorporated pesticides will leach to the groundwater supply—particularly if the soil is highly permeable.

Sprinkler irrigation Sprinkler irrigation sprays water into the air through perforated pipes or nozzles. For row crops, this system poses the least risk to groundwater because water can be applied more precisely than with flood or furrow irrigation. Also, a sprinkler irrigation system makes it easier to put down nitrogen in split applications. With split applications, less N is lost, reducing the risk to groundwater.
Trickle or drip irrigation Trickle or drip irrigation applies water very slowly on or beneath the soil surface near the plant. Because this method doesn't use much water, it is probably the safest in terms of leaching. However, trickle irrigation is not practical for row crops. There is also the potential of overapplication, as with all other systems. Overapplication could mean increased leaching.
field with an irrigation system If possible, delay irrigation for at least one day after applying a chemical. This will give the chemical a chance to degrade and attach to soil particles. If the chemical is postemergent, delaying irrigation will also give the chemical a chance to be taken up by the plant.

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