Water, Water (Not) Everywhere

By Boyd Kidwell
Progressive Farmer Contributing Editor

With 13 pivots to manage, Preston Jimmerson, of Doerun, Ga., realizes how important water is to southwest Georgia farmers. In 2011, Jimmerson installed variable-rate irrigation (VRI) on one center pivot and watched the water savings mount up.

"I wanted to get VRI on one pivot and see how it works, because this is a big investment," says the 28-year-old farmer.

To dip his toe in VRI, Jimmerson selected a pivot fed by an on-farm water-storage reservoir. The pivot covers 90 acres but has a 5-acre area in the circle where crops aren't planted. Besides the non-crop area, the pivot has a 20-acre overlap with an adjoining pivot circle.

"I was wasting irrigation water on 25 acres with every pass plus overwatering the crop in the overlapping area. Using VRI to cut off zones of water on the pivot saves me enough water for an extra irrigation pass every growing season," Jimmerson explains.

In a dry year (such as 2011), this extra irrigation pass results in 400 more pounds of cotton lint per acre. At a price of 75 cents per pound, this is an additional $300 per acre on 85 crop acres under the pivot, or $25,500.

INCENTIVE TO INSTALL

Jimmerson paid a company called Advanced Ag Systems Inc. $12,000 to install VRI on 690 feet of the pivot. To pay for the installation, Jimmerson received an incentive payment of $9,000 (75% of the $12,000) from a partnership between the Natural Resources Conservation Service (NRCS) and the Flint River Soil and Water Conservation District (SWCD). In 2009, NRCS awarded the Flint River SWCD a five-year, $10 million grant to expand water-conservation practices in the Lower Flint River Basin.

After evaluating his $3,000 out-of-pocket investment, Jimmerson plans to install VRI on two more pivots for the 2014 growing season. He'll again select irrigation rigs supplied by storage reservoirs because of the limited water supply they hold. The farm's other pivots are supplied by water pumped from wells in the area's underground aquifer. He plans to eventually install VRI on more irrigation rigs.

"One extra irrigation cycle can be the difference between breaking even on a crop and making a 20% profit over inputs," Jimmerson says.

FLINT RIVER REVIVAL

His work has other positive implications for the region.

The availability of water in the underground aquifer of southwest Georgia and in the Flint River is a serious concern for farmers and the environmental community. The Flint River is a home for endangered freshwater mussels and provides a water supply for the oyster fishery in Florida's Apalachicola Bay.

Years of drought and heavy use for crop irrigation have lowered water levels of the river and underground aquifer. At the same time, farmers in the basin depend on 6,250 pivot systems that help produce $2 billion worth of crops.

In response to this water crisis, farmers formed the Flint River Basin Partnership with Flint River SWCD, NRCS and The Nature Conservancy to install several water-saving practices. VRI is the most innovative of these practices. More than 75 southwest Georgia farmers have been installing VRI during the past five years.

VRI is based on the idea that soil conditions vary greatly across most farm fields, and water needs vary by soil type. Crops growing on light, sandy soils usually need more water than crops growing on heavier soils or in low-lying areas. Farm roads, drainage ditches and wet areas obviously don't need water, but conventional pivot systems apply the same rate of water to all soils and to unnecessary places.

Using VRI technology, these farmers program their pivots to control the rate of water applied, as well as to the areas in the field where water is applied. Using VRI systems, the 75 farmers save 15 to 30% (an average of 17%) of the water required to irrigate crops on 75,000 acres. Combined with other conservation practices, the agricultural community now conserves 15 billion gallons of water per year in the Flint River Basin.

SAVING WATER IN OTHER STATES

Bud Bowers, of Luray, S.C., was fortunate to install VRI on a pivot system five years ago in cooperation with a Clemson University research project. Bowers admits his early VRI equipment isn't very user-friendly, but he can see there's water-saving potential in controlling the rate of water applied based on soil type.

"I may have three to six types of soil across a field, and each of these soil types needs a different rate of water when I run my pivot to irrigate a crop," says the 59-year-old farmer. "I now have one field that has a bay [low-lying area], and I plan to apply for cost-share to install VRI on the pivot on that field so I don't overwater the wet area."

COST-SHARE HELP

South Carolina is one of several states that includes VRI among approved practices in the NRCS Environmental Quality Incentive Program (EQIP) for 2013. Each NRCS region has a list of approved practices, and local NRCS offices are the best place to find out if VRI is eligible for cost-share in your area. South Carolina is part of the NRCS Southeast Region.

To qualify for assistance through EQIP in South Carolina, the field must have a history of two years of irrigation out of the past five years, and the new system must show an improvement in water-application efficiency and water conservation.

Under a typical scenario, EQIP assistance would cover $25,500 of a $34,000 cost to renovate an existing system with VRI components on a 1,300-foot pivot, about 75% of the typical cost. This is an estimated cost; the actual financial assistance will vary for each pivot system.

VRI IN MISSOURI

Rick Heard answers his mobile phone on his way back from visiting farmers in Missouri to talk about installing VRI on existing pivot systems. Heard owns Advanced Ag Systems, in Dothan, Ala., and specializes in retrofitting pivots with VRI. The Missouri farmers Heard met with are primarily interested in using VRI to reduce water-application rates or to shut off water as the pivot crosses heavy soils and wetland areas.

"Farmers are willing to pay for the peace of mind knowing they won't receive an alert at 2 a.m. that their center-pivot tires are stuck in boggy places. They want to use VRI to reduce the application rate of water on heavier soils or cut off the water over wet areas and resume the application as the pivot continues its walk across the field," Heard says.

The irrigation specialist says more data is needed to predict the yield improvement from VRI. In 2013, Heard is working with Monsanto to install VRI on six pivot systems from the Midwest to Texas. Monsanto researchers will collect the yield and water-consumption data. Five of those six pivot systems are located on private farms, and the sixth pivot will be on a Monsanto research farm. The project plans to collect data for five years and measure crop yield changes based on using VRI to match water-application rates to soil requirements.

"We have variable-rate seeding and variable-rate fertilizer application," Heard says. "Variable-rate irrigation is the final frontier."

FIVE-POINT PLAN SAVES WATER

By itself, variable-rate irrigation (VRI) isn't a silver bullet for water savings. However, combined with other conservation practices, VRI contributes greatly to irrigation efficiency. Here's a package of practices used by farmers in the Flint River Basin:

-- low-pressure drop nozzles with end-gun shutoff (reduces water use by up to 23%)

variable-rate irrigation (reduces water use by an average of 17%)

-- advanced irrigation scheduling using soil moisture monitors (reduces water use by up to 15%)

-- conservation tillage (reduces water use by up to 15%)

-- on-farm storage reservoirs that capture water during periods of high rainfall and hold the water for the irrigation season (reduces water use by up to 15%)

(BAS)

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