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GPS-guided center pivot eliminates need for buried wire

Anew GPS-guided, swing arm corner (SAC) for center pivots proved it can eliminate the need for buried wire guidance in on-farm tests in 2002. But the system may not be for everybody or for every center pivot.

A primary use of the SAC is to irrigate field corners, effectively increasing watered acreage. In conventional systems, the SAC swings out to water these areas by following a guidance wire buried in the field.

With GPS providing the guidance, a wire is not needed, which was just fine with Arbyrd, Mo., cotton producers Donald Masters, and his son, Doug, who tested a GPS-guided SAC on their farm last year. “If a wire causes trouble, you have to be out there digging it up,” Doug said. “It's not worth messing with it. My time is more valuable than that.”

The Masterses used the GPS-guided system on a field where grain bins and living quarters only allowed the pivot to “windshield wipe” the field. “About 120 acres was all we could water,” Doug said.

A GPS-guided SAC installed on the pivot was programmed to “swing in to miss our grain bins and the homestead and swing back when it got to the widest points.”

Masters and his father, Donald, purchased a GPS-guided SAC for the 2003 season after the successful 2002 test. The Masterses use “between 40 and 50 center pivots on their farming operation.

“It's all about watering the most acres we can,” Doug said. “Is the GPS-guided system financially feasible? That's a question mark. It is a high dollar investment. If you have 160 acres and you're going to use the swing arm just on the corners, the GPS function isn't as feasible.”

During the summer of 2002, a familiar face on the Masters' farm was Chris Hardy, Hardy Sales, Blytheville, Ark., who set up the GPS-guided, Reinke unit on the Masters farm and monitored its progress. A similar system was tested on the Armorel Planting Co. farm in Armorel, Ark.

“The system is reliable beyond what I've used before,” said Hardy. “We had zero problems with it during the year. Usually new technology or beta systems have lots of problems. We didn't have any.

“It's biggest advantage over burying the wire is that you don't in fact have to bury the wire,” Hardy said. “In this region, we tend to have a serious problem with electrical shorts in underground wire. So you don't have to worry about going out there every time you want to start up the pivot and have to dig up a place to bury wire.”

The system employs two GPS antennas, one at the pivot's control center and another on the swing arm, connected by cable. The GPS on the swing arm “knows” that at a certain degree of rotation, there is supposed be a specific distance between the two antennas. The SAC adjusts to establish that distance, thus moving the SAC in the programmed path.

It may take a couple of attempts to program the most efficient path, but once it's set, it doesn't have to be changed. “The system stores the path of the SAC on a flash card,” Hardy noted. “You can back that up on a computer.”

Changing the path of the SAC is also easy, according to Hardy. All the user has to do is enter the new field coordinates into the software program.

According to Hardy, the system survived the “gripe” test on both test farms last year. “It's like any other customer service business. The fact that users don't gripe about it means they seemed to be pleased.”

On the other hand, GPS-guided SACs “have a way to go before the cost is attractive to growers,” Hardy added. “It's because of the (young) age of the technology.”

The Masterses were able to make the technology pay because of the special circumstances on the field, noted Hardy. “Doug had several acres that he couldn't get with a standard system. Now it rides around the obstacles and gets that pie slice that was being left out.”

According to Reinke, which developed the GPS guidance for the SAC, the system also benefits growers who live in geographical areas where it's difficult to trench wire due to rocky soil. In addition, GPS guidance is not susceptible to lightning, as buried systems are.

Reinke dealers handle the installation and maintenance of the GPS guidance system. The GPS-guided SAC is optional on all new Reinke center pivot irrigation systems and can be retrofitted on existing Reinke systems and most competitor systems, according to Reinke.

Other upgrades include an energy-saving package which maximizes the use of available water and reduces irrigation time by using two separate sprinkler packages on the parent system. Another feature replaces the standard mechanical switches with advanced digital sprinkler control.

Hardy Sales also uses GPS-based technology as a sales tool to show how a center pivot could be set up in a farmer's field, where the wheels will run and where obstacles such as ditches are in relationship to the pivot circle.

“It's a much more accurate design as opposed to old ASCS maps, which aren't always to scale.” noted Bill Hardy, Hardy Sales.

e-mail: [email protected].

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