RAFT RIVER — Nathan Gartner is trying to figure out how to make his irrigation water do double duty so he can maintain profitability while farming fewer acres. He thinks cover crops may be part of that strategy.

Gartner farms within the boundaries of the Raft River Critical Groundwater Area. Even though the area was designated in July 1963, the area has not been subject to curtailments until the 2017 growing season.

Last August, the Idaho Department of Water Resources ordered pumpers in the Raft River Basin to curtail 75 wells covering 6,800 acres of land with so-called expansion rights. This is land that growers began irrigating after they switched from flood to sprinkler systems, arguing that the increased efficiency allowed them to farm more acres using the same amount of water.

The Idaho State Supreme Court ruled those expansions were illegal in 1987. Irrigators were given until two years after the Snake River Basin Adjudication was completed to come up with a management plan for how to stabilize the aquifer. The management plan submitted by the Raft River Groundwater District was ruled insufficient. IDWR officials have said that if the aquifer levels continue to decline, further curtailments may be needed.

Gartner curtailed his water usage this year by 16 percent and dried up 500 acres by turning off endguns and eliminating all hand lines. All but 50 acres of those dry acres were enrolled in the Conservation Reserve Enhancement Program, which pays growers a rental rate for 15 years to maintain a permanent vegetative cover on previously irrigated land.

But he also decided to work with the University of Idaho to inter-seed cover crops in corn silage. One of the challenges with cover crops in water-short areas is that the cover crop requires at least 6 inches of water to get established. But inter-seeding might allow the cover crop to utilize water along with the primary crop, and then finish growing after the primary crop is harvested to provide winter livestock feed.

Gartner farms with his father. They have primarily been crop farmers but are transitioning to more cattle to stabilize their income if additional water curtailments are ordered.

“This is a big step for us,” Gartner told participants on a cover crop tour sponsored by the Minidoka, East Cassia and West Cassia conservation districts. “We are going to cattle while trying to maintain growing feedstuffs for the (nearby) dairy.”

Inter-seeding cover crops is not a new idea, but it’s not common. Gartner worked with Joel Packham, University of Idaho Extension educator in Cassia County, to develop test plots in one corn silage field. They used hand spreaders to simulate seeding by airplane and used five treatments: control, planting the same day as the corn, and then planting in one-month increments after corn planting through mid-August.

“Everywhere there was a gap in the corn, the cover crop did really well. But not enough to ding the corn (yields),” he said.

Based on this first year, Packham thinks planting in mid-June or mid-July has the most potential for success. Studies in other areas have shown that planting a cover crop when the corn is between V-5 and V-6 shows no economic loss to the corn crop due to competition from the cover crop. By mid-August, the last planting date, the corn canopy was too thick for the cover crop to take off.

In addition to the planting date experiment, the Gartners inter-seeded an entire pivot.

The field was planted to triticale in the fall of 2016. After the triticale was chopped this spring, the field was tilled to the depth of 3 inches.

“That just pulled up root balls — we had a gnarly seed bed,” Gartner said.

To compensate, they bumped the seeding rate to 42,000 seeds per acre and ended up with a plant population of 34,000 to 36,000 per acre. Next year, he plans to shoot for 38,000 to 40,000 seeds per acre and will probably plant a flex ear hybrid to compensate.

That field was cultivated and the seed flown on with a plane at V-6. He plans to let the cows graze it this winter, and then plant malt barley in the spring.

Harvest was hard on the cover crop. “Every where the trucks ran, the cover crop stopped growing,” Gartner said. He had been advised to run the pivot after harvest to loosen the truck tracks, but chose not to.

“We probably lost some growth.”

“This is a big step for us. We are going to cattle while trying to maintain growing feedstuffs for the (nearby) dairy.” Nathan Gartner, Raft River Critical Groundwater Area farmer
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