181-15 Corn Response to Nitrogen After Alfalfa As Affected by Tillage and Regrowth.



Tuesday, October 18, 2011: 1:15 PM
Henry Gonzalez Convention Center, Room 213A, Concourse Level

Jeffrey A. Coulter1, Matt A. Yost2, Michael P. Russelle3, Craig C. Sheaffer1 and Daniel E. Kaiser1, (1)University of Minnesota, St. Paul, MN
(2)Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN
(3)Department of Soil, Water, and Climate, University of Minnesota-Twin Cities, St. Paul, MN
Current N guidelines for corn following alfalfa in Minnesota suggest that when compared to corn following corn, N rates for first-year corn after alfalfa can be reduced by 168 kg N ha-1 when ≥43 alfalfa plants m-2 are present at termination. Two unanswered questions regarding N availability to first-year corn after alfalfa relate to the timing of primary tillage for alfalfa termination and the amount of alfalfa regrowth incorporated. In 2010, experiments were conducted in first-year corn after alfalfa on six farms in southern and central Minnesota with medium- to fine-textured soils and ≥43 alfalfa plants m-2 at termination. The response of grain and silage yields to N fertilizer was evaluated within four combinations of alfalfa regrowth management (regrowth after early September left in place or harvested) and tillage timing for alfalfa termination (disc-chiseling in the fall vs. spring) on each farm. Corn grain and silage yields were not affected by regrowth management or tillage timing on any farm. There was above-normal potential for N loss at these farms, as precipitation from 1 Oct. 2009 to 31 Sep. 2010 was 20 to 57% above the 30-yr average. Corn grain yield ranged from 11.3 to 14.5 Mg ha-1 among farms, and grain and silage yields responded to N fertilizer on just one of six farms. At this farm with above-normal rainfall and poor draininage, net return to N fertilizer within $2.50 ha-1 of the maximum for grain yield occurred with 76 to 90 kg N ha-1, assuming $0.99 kg-1 N and $206.71 Mg-1 grain. Similarly, silage yield on this farm was increased by 13% with 110 kg N ha-1. These results demonstrate that on highly productive medium- to fine-textured soils in the Upper Midwest with ≥43 alfalfa plants m-2 at termination, first-year corn grain and silage yields are often maximized without N fertilizer, regardless of alfalfa regrowth management or the timing of primary tillage for stand termination.
See more from this Division: ASA Section: Agronomic Production Systems
See more from this Session: General Agronomic Production Systems: I