Six simple steps to a better pivot
Advancing technology is making it easier than ever to monitor your center pivot status, but you don’t necessarily need the latest bells and whistles to eyeball some problems in your system early in the season.
“Operate the system when crops are small, and look for broken or plugged sprinklers and pressure regulators. Also look for leaks,” says Darrel Martin, University of Nebraska water resource engineer.
At a glance
• Checking your pivot system early on can pay dividends.
• Water runoff is a big concern, leading to inefficiency.
• Incorrect nozzle sizing and placement are other problems.
Martin provides the following checklist that will help you save pumping costs, prevent water runoff, improve uniformity and even increase yields.
• Check for runoff. This is Martin’s No. 1 condition to guard against. “If water is running 50 feet out in front of the pivot, you’ve got a problem,” he says. His recommendation: Go to the steepest part of the field at the outside of the system and see what’s happening as far as runoff. About your only remedy to this wasted water during the season is to speed up the pivot, which means this problem requires a longer-term fix. Among those fixes: Increase the wetted diameter of the sprinkler, reduce water output to the pivot while being careful to meet crop needs, and increase soil surface storage through more surface residue and special tillage tools such as a dammer-diker. No-till will improve your soil’s water infiltration rate.
• Check pressure at the pivot point. Monitor pressure and flow rate and know what the pressure is supposed to be. If the pressure is wrong, your system isn’t operating right. Martin cites an example in which a system’s pressure at the pivot point was 75 psi and the pressure regulators were set at 25 psi. The system was basically pushing water through a closed valve, wasting money in energy costs. Pressures that are too high at the pivot point hike operating costs and pressures that are too low cause poor uniformity. He recommends buying a pressure gauge, for only $25 to $30, to measure pressure at the pivot point and at the end of the system.
• Check installation and maintenance. He’s seen plenty of pivots where nozzles are at the wrong locations, or are broken, and pressure regulators are plugged — even cases where the entire sprinkler package was installed incorrectly. Walk the pivot early before the crop is too tall to detect faulty nozzles. Another problem is an inappropriately adjusted end gun.
• Check if system capacity is falling off. Several things, including the groundwater table lowering through the season, could reduce output. Make sure the sprinkler package matches capacity. “The system may do fine in the first irrigation, but check in July and August as crop water demand rises and rainfall drops. Get ahead of the game in late June or early July by making sure soil moisture is adequate,” he says.
• Check sprinkler placement. Fewer and fewer pivots have sprinklers lowered into the crop canopy, and Martin thinks that’s a good thing. The sprinkler pattern is interrupted by the growing crop, which leads to poor uniformity. He recommends placement no lower than truss rod height.
• Check for inadequate monitoring. “You can’t manage what you don’t measure,” he says. He highly recommends using a well flow meter.
“Center pivots are billed as 90% to 92% efficient in application of water,” Martin says. “But that’s the potential. It’s not what actually happens in the field without proper monitoring and management.”
This article published in the June, 2010 edition of NEBRASKA FARMER.
All rights reserved. Copyright Farm Progress Cos. 2010.