Photographer's Note


In farming irrigation, a center pivot system as shown in the photo is very popular in the flat area. It pivots around a central point known as the "pivot point" or "pivot pad". Center pivots come in a myriad of sizes, from 1 acre up to 400 acres or more. This method is economical when 40 acres or more are irrigated under a single pivot. Irrigation of various field sizes is made possible by using a variety of lengths of "spans" between the supporting "towers". Combining several different lengths of spans enables accommodation of almost any size field. The center pivot is fixed at the pivot point and rotates to irrigate a large circle (a radius of 200 meters up to 1000 meters). The longer the pivot, the larger the area covered and the lower the cost per hectare. The water enters the system at the pivot point. The control panel, fertilizer injection equipment, and often the pump unit itself are located at the pivot point; the center of the irrigated circle.

Center pivots generally have an end gun attached to the last tower on an end boom to increase the irrigated area. Since this end gun is supported on an extended boom and does not have a supporting tower directly under it, this addition can greatly increase a pivot's irrigated acreage without requiring additional land clearing. For instance, a 750 foot long pivot installed on a given field will cover 40.5 acres. Add an end gun capable of irrigating another 120 feet and the irrigated acreage is increased to 54.5 acres if the gun is able to operate for the entire circle. The end gun can be automatically shut-off when we need to skip non-crop areas such as residence yards, buildings, roads, or forests…

The major advantages of the system are the low labor requirement and the circular travel path. Operating a pivot is a simple job of turning the pivot on and can be done easily by one man. The circular travel path means that the pivot will end its irrigation cycle at the same point where it initially started, so the next irrigation cycle will begin at the driest point in the field.

The major limitation is its circular travel path. Since the entire machine moves as a single line of spans and towers, the spans at the outer edge of the field must travel considerably faster and thus cover more area than those near the pivot point. This means there is a point where applying a given amount of water from these end spans is not possible due to soil characteristics or pump and piping limitations. If the pivot requires 96 hours to apply a given amount of water to the field and the crop growth stage, climate, and soil type determine that this amount of water is needed every 72 hours, the irrigator will "fall behind", and still need to be considered for improvement.

(Source: Irridelco)


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Additional Photos by Ngy Thanh (ngythanh) Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 471 W: 125 N: 2332] (8458)
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