Variable-Rate Fertilization for No-Till Farms

By Jim Steiert on April 26, 2017

Variable-Rate Fertilization Works for Palouse Farmer Eric Odberg

ERIC ODBERG knows well the challenges of thin soil atop rolling hillsides, which slope as steeply as 45-50 degrees in the Palouse.

eric ddberg

Despite hills that slope as much as 50 degrees, Eric Odberg is able to keep the right amount of nutrients where they need to be through no-till, fertilizer banding and variable-rate technology.

No-tilling 2,200 acres of winter and spring wheat, malt barley, garbanzo beans, canola, millet, sunflowers, quinoa and flax in Genesee, Idaho, the area lacks summer rainfall, and when it does rain or snow, erosion occurs from too much water coming off the hillsides too fast. Still, his wheat yields are usually above the county average of 85-90 bushels — his recent winter wheat yielded 102 bushels per acre. That comes on terrain where hilltops may yield only 50 bushels per acre, while bottoms and meadows may hit 140 bushels. Keys to Odberg’s farming success in this challenging landscape include using no-till to keep cover on the soil so that soil moisture doesn’t evaporate, using a variety of rotational crops, soil- and plant tissue sampling annually, yield mapping and variable-rate fertilization.

Technology Efficient Most of Odberg’s farm drains into the Clearwater River, a salmon-bearing stream crucial to spawning, he says. “I can sit in my tractor seat and see exactly where Catholic Creek, a drainage of the farm, drains right into this environmentally sensitive salmon stream,” he says. “I’m very conscious of what leaves the field via the creeks — I want the fertilizer to stay on the farm.” He finds the best way to take care of that concern, while saving money, is to avoid applying too much fertilizer in the first place. That means soil and tissue testing in season, creating variable rates for all fertilizer applications based on yield maps and infrared imaging, using auto-boom control, banding anhydrous ammonia and liquid fertilizers, and applying starter fertilizer as a liquid in-furrow. Among the first to enroll, Odberg took advantage of the NRCS’ Conservation Security Program in 2006 for assistance in acquiring yield monitor and fertilizer rate controller equipment. He realizes a 7% savings with variable-rate fertilization and another 8% with auto-steer, for a total of 15% savings by using fewer nutrients more efficiently Odberg also began a soil liming program 5 years ago, broadcasting 1 ton per acre each fall. It’s brought up soil pH levels and increased wheat yields by as muc

h as 15 bushels per acre in wetter years. At a cost of $70 an acre, he limes only one field each fall, and hopes to variable rate his lime one day as well. “I save money by not putting on nutrients I don’t need. I know which areas of the farm are low in productivity and which areas are high,” Odberg says. “A lot of it comes down to water-holding capacity — it’s more obvious here. We face a real challenge increasing soil organic matter on the hilltops.” A fourth generation farmer, he notes that former family members had livestock, and he may look at bringing that back to his operation to add more organic matter. “For now, we are protecting the soil, holding moisture and managing fertility with the best means we have available,” he says.

Jump Start At the heart of Odberg’s fertility program is banding nutrients in a one-pass no-till application with a John Deere 1895 air drill. The drill is rigged with mid-row banders modified to a 19.6-inch diameter in three ranks on 20-inch centers. He seeds on 10-inch centers and fertilizer is applied 5 inches to the side and 5 inches below the seed. He finds starter fertilizer critical to getting the crop going and uses a formulation including 13.7% nitrogen (N), 27.5% phosphate, 2 pounds of zinc, and humic acid. Magnesium is added, depending on soil testing, and 10% of the phosphate is Orthophosphate. “With the starter fertilizer program, fertility is available right away and jump-starts the crop quickly so it can grow right into the deep fertilizer,” Odberg explains.

Adjusting Anhydrous For anhydrous ammonia application, an ammonia bottle rides on the tongue of the rig, giving the advantage of short coupling to allow better navigation of hillsides with less draft. Odberg adds weight to the drill and down pressure on the wings to keep the drill in the ground on the varying terrain. Anhydrous ammonia is channeled through an Exactrix TAPPS pump that liquefies the gas from the tank at high pressure so it goes into the ground as a pure liquid rather than a gas. The drill is modified with Keeton seed firmers, and Thompson closing wheels follow the fertilizer injector to keep fertilizer in the soil. “Ten years ago, I didn’t like a lot of the fertilizer systems that were available on drills,” Odberg says. “That’s when Guy Swanson of Exactrix showed me the high-pressure anhydrous ammonia fertilizer system with liquid phosphate and sulfur. It had great uniformity across the drill and the TAPPS system reduced the fertilizer rate by 20 pounds per acre. “Most fertilizer systems reduce the pressure where anhydrous ammonia is applied, but we’re increasing it to get the liquid at the injection point. With environmental concerns, it’s especially important that the N stays where it’s placed. The variable rate fertilization has proved to be easily attained with yield monitors and infrared mapping. Monitoring equipment can change from low to high fertility rates in 1-1½ seconds across zones in the field.”