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MADISON, Wis. - Lack of rain doesn't worry Paul Onan as much as it once did. The dairy grazier from Amherst Junction, Wis., has been irrigating half his pastures for four years.
Onan talked about his pasture irrigation experiences as part of a series of grazing seminars during the recently completed World Dairy Expo in Madison, Wis. The dairyman has been on his sandy loam farm in the central part of the state for 15 years.
The farm has 80 acres of pasture that support Holsteins and crossbreds. Onan's pastures are mainly orchardgrass, Kentucky bluegrass and a variety of legumes.
He said he wanted to try irrigation after several years of below-average rainfall and below-average pasture production. Onan ended up working with the Golden Sands Resource Conservation and Development (RC&D) Council to study pasture irrigation.
In 2009, with a grant from the Grazing Lands Conservation Initiative, the RC&D bought two 12-pod K-Line irrigation lines to test on Onan's farm. That brand of irrigation system was chosen due to its affordability. The company's pods are plastic containers that sit on the ground and hold the actual sprinklers. Pods are connected by lengths of water tubing.

Well, equipment: $22,183
The irrigation equipment cost $9,628. That figure includes four 500-foot rolls of three-inch water pipe; 1,200 feet of tubing; 24 pods and sprinklers, miscellaneous parts; labor for installation; and sales tax.
In addition, Onan needed a well and pump. The 103-foot-deep, six-inch-diameter well cost $6,755, while the pump ran $5,800, for a subtotal cost of $12,555. All tallied, the equipment, well and pump cost $22,183.
Theoretically, the well can pump 100 gallons of water a minute. That's enough for three lines of pods, Onan said.
Forty acres of the Onan farm were available for irrigation, but the research project covered just 20 acres. Ten acres were actually part of the study, and 10 more received water because of the way the system was designed and used.
Twelve research strips were laid out. Each one measured 50 by 600 feet, and they were in two paddocks. Each strip was about 0.75 acre and was the amount each 12-pod line could irrigate without being moved. When he does need to move the lines, Onan uses an all-terrain vehicle.
Unirrigated, control strips were also laid out. The amount of water applied to two of the research strips was measured with soil moisture sensors. Onan irrigated the rest of the strips as he felt necessary.
Irrigation began on both paddocks on July 1, 2009. Onan said that was about two weeks later than he would have liked, but the system wasn't ready earlier. Irrigation concluded Sept. 24.
At first, irrigation took place only at night, to use lower electrical rates. After 12 hours of applying water, Onan moved each pod. Using this schedule, each control strip got two inches of water in 24 hours.
A week of irrigating overnight did not show any increase in pasture production. So 24-hour irrigation started, with each line moved every 12 hours. That meant 0.75 acre got two inches of water in 12 hours.
Overall, each strip received 9.5 inches of water. Onan had taken his cattle off the paddocks on June 15, because of a lack of grass. But the irrigation let him turn them back out on July 20.
A digital pasture plate meter measured plant growth each week. Forage samples were collected and analyzed for quality. Onan did not apply any fertilizer to the plots.
Onan described the summer of 2009 as very dry. His farm got 7.5 inches of rain between June 15 and Sept. 30, well below the normal amount of 15.5 inches. His pastures went dormant near June's end, requiring him to provide other feed.
His unirrigated pastures yielded just 0.51 ton of consumable dry matter per acre. In contrast, his irrigated pastures yielded 1.98 tons.
That kind of yield increase was worth $258.75 per acre, according to Golden Sands RC&D. Owning the irrigation equipment and well during 2009 cost Onan $107.06 per acre, while it cost him $82.34 to operate. All tallied, the total cost of the setup in 2009 was $189.40 per irrigated acre. And the gain from irrigating amounted to $69.35 per acre.
If Onan had irrigated 40 acres instead of 20, and if the increase in dry matter was worth $150 per ton, his ownership cost would have been cut in half. At the same time, his gain from irrigating would have risen to $122.88 per acre.

Wet year compared
While 2009 was dry, 2010 - the second year of the research - was abnormally wet. Onan's farm got 24.5 inches of rain between June 15 and Sept. 20, compared to the usual 15.5.
Because of all that rain, the test strips received only 2.5 inches of irrigation water. So during 2010, there was "not a significant difference in production averages between irrigated and non-irrigated forage yield," according to the RC&D.

Conclusions
The researches arrived at several conclusions. Among them:
• Without a production response, no investment in irrigation would pay.
• A response to irrigation is more likely on soils that have low water-holding capacities.
• Improved yields more than covered the annual costs of irrigation on Onan's farm during 2009, but not in 2010.
• Don't assume that all the additional plant growth provided by irrigation will be in the vegetative stage that livestock will eat and do well on. So don't value all the extra growth the same.
• Onan's irrigation system should pay for itself if: He can irrigate 40 acres during dry years; he gets 1.5 to 1.75 tons more dry matter per acre; his dairy herd eats that extra dry matter; and all of the above happens in at least one year out of three.

Third line added
In 2011, Onan installed a third irrigation line. He said he was amazed by the changes in his pastures. He said, "With water, you can really get grass to grow." "
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