Two important systems for irrigating crops-drip irrigation and variable-rate pivot irrigation-are gaining converts as the equipment and technology is improving. Additionally, measuring when and where to apply water is becoming much more sophisticated.

Bill Cox, Coxco Ag Services, Inc., Las Cruces, N.M., recently provided insight in how drip irrigation began being used in his area in the early 1990s, and as of 2007, it accounted for 90 percent of the pump irrigation. He is confident the percentage is even higher today.

The turnover in systems and methods in the Las Cruces area has meant:

  • Water today is injected beneath the crop rather than running in furrows beside the crop.
  • Drip systems today are improvements from when Cox began installations in 1993.
  • It only took three years for the technology to prove its value ('93-'96).
  • Recently Environmental Quality Incentive Program (EQIP) federal funding has accounted for a good amount of drip irrigation installations.

Cox told crop consultants at the National Alliance of Independent Crop Consultants annual meeting to look at the potential for drip irrigation in their service area. "You can be the go-to guy in your area," he said.

"There is a steep learning curve," he said. "You need to be sure to charge enough for your time because it will be time consuming to consult." Farmers/growers will require considerable information for reassurance and understanding what is happening with a new cropping system. The consultant will also need a constant flow of information from the farmer to understand how to oversee use of the drip system.

Cox noted a few advantages he has observed to drip:

  • Dramatically increased yield compared to furrow irrigation.
  • Crops grow under optimum moisture conditions more than with pivot or furrow irrigation.
  • Injection of nitrogen (N) through this system results in less N being required to grow a crop.
  • Ground is always dry enough to harvest, and crops like vegetables can be watered just before harvest to sell water weight.
  • There can be a dramatic reduction in the heavy tillage used and savings associated.
  • Fewer cultivation trips are required with less water for weeds outside the crop bed.
  • Less wind and water erosion is because the high crop beds don't dry out completely between waterings.
  • Water that would normally be wasted by other irrigation methods is available to water additional acres.

Although Cox noted that drip irrigation is used for cotton, alfalfa and other non-vegetable crops, he started with vegetable crops in 1993. An example of a drip irrigation advantage is the higher yield in growing green chilies. In 1993, a field's green chili yield was 16 tons per acre using furrow irrigation, and in 2005 the yield on similar soil using drip irrigation reached 33 tons per acre.

Drip irrigation systems are typically designed to deliver at least 0.35 of an inch of water per day, Cox noted, although different crops require differing amounts of water. For soils in his area, cotton can be grown with 0.25 inch of water per day, but a crop like onions might require 0.5 inch per day.

"If you're meticulous about maintenance, drip systems will last indefinitely," Cox said. He consults with growers who still have their original drip tape and other original equipment from 1993 still in use.

Variable Rate Pivot Equipment
Jay Holder, Holder Ag Consulting, Ashburn, Ga., introduced attendees to the on-farm field use of variable rate irrigation systems. He noted his work with the University of Georgia precision agriculture team, Natural Resource Conservation Service, Nature Conservancy, Flint River conservation district and Farmscan (Australian precision controller company).

Installations in general have been financed with EQIP and Conservation Innovation Grant (CIG) money on a 75/25 cost share grant. The projects began in March 2004 with the first installations, and today there is commercialization of equipment that has been developed. A total of 47 pivot irrigation systems have been retrofitted with variable rate equipment and controller software.

The importance of the equipment Holder has been installing is that it allows "more than one way to adjust rates." The pivot speed can be adjusted, sections of drop nozzles can be cycled to shut off and turn on based on a variety of factors-boggy section in a field, overlap with another pivot, soil variations, ponded water in a field, soil nutrient differences and different crops in parts of the irrigation circle.

For example, if a sandy area in the field needs more water than the 100 percent base rate, the pivot will slow down and those nozzles over the sandy area will remain on; the rest of the nozzles will cycle to apply the correct rate for the other soil type. Pressure issues are controlled with a cycle-stop valve.

"We are using the equipment to cut water off where we don't want it as much as adjusting the flow rate," Holder said. Variable rate irrigation can save millions of gallons of water. On average, field research has shown a water savings in the neighborhood of between 12 percent to 16 percent per crop year per irrigation circle, he proclaimed.

All of the installed systems have compressed air operating the control solenoids. All use electricity for their power supply. Each of them has to have GPS installations. Application maps that load into the special controller are produced off of a computer terminal.

Because of all the different pivot brands and nozzle spacings, "we've had to make it up on the go" in terms of installing equipment on various pivots.

Cost of all the equipment and controller system is a concern in going from prototypes to commercial systems.
"Farmscan is upgrading the controllers," Holder noted. "This includes making them more compact and offering eight control zones for about 40 nozzles in a basic package."

All types of precision ag data collected from yield monitoring, grid soil sampling, EC mapping, drainage and much more can be used to compile the controller map.
Beyond plain water application, experience with dairy lagoon nutrient application is now being gathered. Holder said a couple installations for pumping lagoon waste onto soil have been completed and plans are for more installations to be equipped for nutrient management.

Flow control and avoiding sensitive areas with lagoon waste is definitely as important as appropriate watering for crops. "There is a lot of interest in being able to keep runoff from going in waterways, getting into ditches and ultimately the rivers," Holder said.

New Moisture Monitoring
After going through the various soil moisture monitoring techniques and equipment available for use in his Plainview, Texas, area, Bob Glodt, Agri-Search, Inc., introduced consultants to the AquaSpy capacitance probes.
"This equipment has taught me more about irrigation than anything else I've ever used. The information is extremely comprehensive," he said.

Although Glodt carries a soil hand probe everywhere he goes, and experience allows him to make a lot of on-the-go decisions about irrigating, nothing he has seen provides the extent of data available through the electronics of Aquaspy.

Probes, normally 40-inches long, are placed in fields to provide moisture readings at four-inch intervals from top to bottom. The battery-powered unit takes moisture readings automatically every 15 minutes. Radio or cellular transfer of data from several probes occurs with the telemetry being connected to the internet for downloading to a computer.

Glodt said there is a big learning curve in understanding the graphs generated, but the ultimate result is that a consultant can do a superior job in working with irrigation. Glodt noted, "AquaSpy equipment allows growers or consultants to better understand soil recharge rates after water is applied, as well as being able to better evaluate the effectiveness of an irrigation in wetting the zone where the most active water uptake is occurring."