Irrigation is essential in sod production, according to Martin Williams, farm manager for New Life Turf, Inc., which grows 400 acres of Bermuda and Zoysia for use on golf courses and sports fields.

Irrigation can be a problem, however, if you have 50 acres with a wide range of soil types from sand to muck clay and undulating topography that puts the highest point in the field eight feet above the spot where the center pivot is anchored.

“When we applied water so we could harvest the sandy areas at the top of the hill, the bottom of the field would be flooded,” said Williams.

Then, in March of 2005 Richard Hallman, technician for Ahmad Khalilian, agricultural engineer at Clemson University's Edisto Research and Education Center at Blackville, called to ask if New Life would be interested in trying a variable rate irrigation (VRI) system.

VRI allows the irrigation nozzles to be pulsed in variable-length cycles and the pivot speed to be varied, so that a farmer can put the right amount of water exactly where it is needed, according to Khalilian — no more uniform watering of non-uniform fields.

Under a $500,000 grant from the Natural Resource Conservation Service, Clemson University was authorized in 2004 to install three VRI systems in South Carolina. Under the same grant the University of Georgia is to install 15 systems in that state. The system at New Life was the first in South Carolina, installed the first week in May last year.

A similar system was also installed the same day on a pivot in a 68-acre field farmed by Drake and Moss Perrow at Cameron in Orangeburg County. They grew cotton there in 2005, but had so much rain the VRI system was used only once.

The third system was installed in December on a pivot in a 100-acre Darlington County field farmed by Edwin Dargan.

“Sod quality is our No. 1 priority,” said Williams. “One key to quality is uniform soil moisture. The VRI unit allows us to apply the perfect amount of water. By heavily irrigating sandy soils and lightly irrigating clay soils we ensure sod uniformity, and save water as well.”

“VRI can also mean less energy is used for pumping, less water runs off the field and less pollution reaches streams,” said Khalilian. He has not collected data yet to show just how much water has been saved on the two systems used in 2005, but he expects the figures will eventually compare to three installations in Georgia that have saved from 1.4 to 2.8 million gallons annually.

Williams uses a computer program called FarmScan to enter a combination of GPS coordinates and soil types in order to control water distribution. Total cost of the software and installation of controllers on every nozzle and the equipment to turn them off and on was about $12,000.

Clemson University paid $9,000 from grant funds and New Life Turf paid $3,000.

Khalilian said that about 2,000 center pivot systems are located in South Carolina. Not every one would benefit from VRI, but many would. He said more efficient irrigation can increase productivity because every area receives the right amount of water. Boggy areas get less, sandy areas get more, roads and waterways get no water and pivots can overlap without overlapping water applications.

“With VRI farmers don't have to farm under a pivot in half or quarter circles anymore,” he said. The center pivot VRI equipment is from a company called Hobbs & Holder, which licenses the technology from the University of Georgia, where it was developed.

Technology for lateral variable rate irrigation systems has been developed at Clemson University's Edisto REC and will be available commercially in the near future.

Farmers who are interested in converting to VRI can take part in a cost-sharing program under the Environmental Quality Incentives Program (EQIP), according to Stephen Henry, environmental engineer with the NRCS office in Columbia.

“March 31 is the deadline for applying for 2006,” he said. “The easiest thing to do is contact your local conservationist.” Henry said that the cap is $15,000 per system.

“Growers will have to pay for mapping of fields to provide the GPS information necessary to make the variable rate system work. The cost sharing is only for equipment conversion,” he said.