Efficiency is biggest irrigation challenge WITH LIMITED WATER supplies, high energy costs and low commodity prices, farmers must make certain irrigation systems operate efficiently and economically to assure profitable yields.

"The challenge," says Edwin Smith, "is to get every plant the same amount of water. To do that, we have to apply the proper amount of water through every nozzle."

Smith, Senninger Irrigation, Inc., and Eddie Rhoderick, Rhoderick Irrigation, Silverton, Texas, offered maintenance and trouble-shooting tips to growers during a recent Texas Agricultural Irrigation Association seminar in Amarillo.

Smith said problems with overhead irrigation systems will be either mechanical or hydraulic. He discussed hydraulic issues, and Rhoderick addressed mechanical and electrical problems.

Crop uniformity, application irregularity, soil and field conditions fall under the hydraulic umbrella, Smith said.

"The first chore is to identify the problem," he said.

"If it's a total system failure, the entire crop will show problems. If the failure occurs at the end of the system, consider the possibility of low pressure making less water available.

"Problems at the front of a system may show up as overwatering under the first few spans. Look for higher plant growth," he said.

Problems in the middle of the system could indicate sprinkler failures.

Smith said in some cases the sprinkler package might not match the system. "In some cases water availability may have changed since installation."

Field elevation also affects application uniformity, "especially with a hill at the end of a system. Friction loss may mean too little pressure to push water up the hill."

Smith advises farmers to match pressure needs to pipe sizes along the entire system.

Farmers also should check for leaks. "Leaks apply more water in some locations than others. Runoff, especially following rainfall, may result."

Overwatering often occurs at the front of a system. Smith recommends installing the "smallest nozzle possible that will not stop up. Also, decrease pressure for the first space or two.

"If the front of a system applies too little water, look for stopped-up nozzles. Rust or a small piece of pea gravel may get into the system."

Smith says wider spacing and nozzles that overlap will prevent overwatering.

In the middle of a system, elevation changes may affect pressure and application uniformity. Regulators may help, Smith said. "Any part of a system that is lower than the rest will have greater water pressure unless the system is regulated."

He also recommends selecting a pad for nozzles that will throw water the proper distance.

"A lower trajectory needs a different pad than a higher one," he said. "And heads need to stay flat as they run; otherwise, they throw an erratic pattern."

Drag tubes may also display erratic applications if not run properly. "Drag tubes should be in the row with at least three-feet dragging in the soil. Otherwise, wind can blow the hoses off course."

He also recommended circle rows for drag hoses. "Application can be more accurate," he said.

He said low-hanging nozzles require shorter intervals when crop height is above the nozzles.

"Control droplet size on sprinklers. The finer the droplet, the more it evaporates. Droplet size is even more important when water is limited. Low Energy Precision Application (LEPA) systems keep water where it's applied. Also, crop residue and dikes help hold water in the rows."

Rhoderick said farmers can handle many mechanical problems on their own, but sometimes will be better off to call in an expert.

"The best troubleshooting practice is preventive maintenance," he said. "Always check and maintain gearboxes, U-joints, drive shafts and tires. Keep electrical systems as clean as possible. Practical maintenance the first of the year will eliminate many problems."

He said when a tower shuts down behind the rest of the system, the problem likely occurs in the tower itself. He says the motor, gearbox or a flat tire could be the culprit.

"It also could be a micro-switch or set of contacts."

A tower ahead shutdown could be caused by a stuck contact or a micro-switch. "Most irrigators can handle an ahead or behind tower shutdown," Rhoderick said.

Inline problems could be more serious.

"Check incoming power to make certain the 480 (480 volts) power is available," he said. "Things may get complicated after that and we recommend irrigators call for help. If they try to fix it themselves and still need to call us, we can't tell where the original trouble started."

He also emphasized that farmers should shut the system down before attempting any electrical work. "Make certain the system is properly grounded."

Rhoderick said an irrigation farmer should visually check every nozzle on a LEPA system. "He can't do that from the road, but must get into the field and check one at a time."

Smith and Rhoderick advise changing nozzles when water level drops. "If the level goes down, the system does not apply enough water with the same nozzles," Rhoderick said.

They recommend a pressure gauge at the end of the system. "That's the most accurate place to put it," said Smith.

Sith and Rhoderick say irrigation systems can be complicated but good maintenance and timely repairs will save farmers time, money and promote effective and efficient irrigation.