In Idaho, New Tillage for a New Crop

Southern Idaho is known for its prodigious yields of potatoes and sugar beets, but the state’s growing dairy industry is also supporting the production of a different crop—corn. So David Tarkalson and David Bjorneberg, who work at the ARS Northwest Irrigation and Soils Research Laboratory in Kimberly, Idaho, conducted a 2-year study to see whether farmers who use conventional methods of tillage and fertilizer application could increase corn yields by banding fertilizer with strip tillage instead.

Farmers using strip tillage make just one pass through fields before planting. When they use strip tillage, they remove residue from a 6- to 12-inch-wide strip and till the soil 6 to 8 inches deep with a knifelike shank, which can also inject fertilizer.

Tarkalson and Bjorneberg studied corn yields from one field in 2007 and one in 2009, both of which had been planted with alfalfa the year before. (Research was not conducted in 2008 because a field was not available for study.) In both years, one of the study areas was located at the top of an eroded slope, and the other was located at the bottom of a slope, where soils eroded from higher elevations had accumulated.

The scientists used either conventional tillage or strip tillage and applied nitrogen and phosphorus to the fields either by broadcast application or by subsurface injection with the strip-till shank.

The scientists found that using strip tillage to place fertilizers 6 to 8 inches directly below the seed increased corn grain yields on the nutrient-depleted eroded area by 12 percent in 2007 and 26 percent in 2009, compared to the other fertilizer-placement treatments. This translated into yield increases of 11 to 26 bushels per acre.

Though band placement of nitrogen and phosphorus on higher slopes was especially beneficial to boosting yields, at lower elevations the technique resulted in the same yields as broadcast fertilizer applications. These findings suggest that Pacific Northwest corn growers who apply fertilizer in bands with strip tillage could help lower production costs by reducing tillage while maintaining or increasing yields.—By Ann Perry, Agricultural Research Service Information Staff.

David Tarkalson and David Bjorneberg are with the USDA-ARS Northwest Irrigation and Soils Research Laboratory, 3793 North 3600 East, Kimberly, ID 83341; (208) 423-6503 [Tarkalson], (208) 423-6521 [Bjorneberg].

"In Idaho, New Tillage for a New Crop" was published in the August 2011 issue of Agricultural Research magazine.