My first trip to Arizona from Texas, and I see all of these circles on the ground in all different shades of green. Some had patterns through them, and others looked like pie charts.|||The first answer misses one detail - there is a sprinkler in the middle - but it is a huge long arm that pivots in the middle and travels around in a circle with sprinkler heads on top. The partial circles (sectors) are limited plantings, where the water is turned off for part of the turn or reversed in direction.|||Those are actually regular fields. Why circular you ask? There is a sprinkler in the middle and if it was rectangular or square it couldn't get water to the whole field. It's kinda an efficiency thing.

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