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— Irrigation —

One of the oldest methods of irrigating fields is furrow irrigation, where farmers flow water down small trenches running through their crops. It is one type of flood irrigation.

Flood irrigation is not the most efficient irrigation method, but it is cheap and low-tech. Although less water is lost to evaporation than in spray irrigation, more water can be lost from runoff at the edges of the fields.

The photo shows a common high-pressure spray irrigation system in operation. The horizontal tube carries water from a pump at the center of the system. All along the tube, which can be thousands of feet long, there are triangular frames with wheels. The whole thing rolls around the fields using the center point (the pump) as the pivot. Water is sprayed from sprinklers all along the tube. Thus, a large, circular pattern of land is irrigated. You've might have looked down during an airplane flight and seen circular patterns of green on the ground -- these are center-pivot irrigation patches.

The small horizontal pipes running just above the ground (shown in the photo) are slowly dripping water. Drip irrigation is one of the more advanced techniques being used today because, for certain crops, it is much more efficient than traditional spray irrigation.

In drip irrigation, water is run through pipes (with holes in them) either buried or lying slightly above the ground next to the crops. Water slowly drips onto the crop roots and stems. Unlike spray irrigation, very little is lost to evaporation and the water can be directed only to the plants that need it, cutting back on water waste.