My understanding is that many farms in the midwest (as least corn farms) don't irrigate - rainfall is sufficient. Linear and circular systems should in princip

My understanding is that many farms in the midwest (as least corn farms) don't irrigate - rainfall is sufficient. Linear and circular systems should in principle be able to achieve the same water efficiency (within their swept area). They're the same thing - an above ground wheeled mechanism to deposit water. If you're farming in an area where you're water constrained, then you might not necessarily care about parts of your field not being used (as long as it's reasonably small), since what you care about is your input to output cost. Some advantages of central pivot is that: a) you only need to feed water to a single fixed point - in a linear system you either need a ditch to draw out of (that's water loss right there), or drag a hose around (that's a possible point of failure) b) you don't need to figure out how to regulate the two ends of your line to keep them in line.