Establishment of Switchgrass In Corn Influenced by Switchgrass Variety and Landscape Position.

Switchgrass (Panicum vigratum L.) is a perennial C4 grass species native to North America and has been identified as a potential feedstock for bioenergy production.  This perennial species requires two to three establishment seasons before reaching maximum dry matter production, increasing the opportunity cost of producing other crops on the same land.  An experiment was conducted testing establishment of two varieties of switchgrass underseeded into corn using Atrazine and 2-4-D across a landscape gradient.  The underseeded switchgrass treatments were compared to a corn control that used glyphosate for weed control and contained no switchgrass.  Stand frequencies of switchgrass were taken the spring after establishment.  Grain yield was reduced 1.95 Mg·ha^-1 in underseeded switchgrass treatments.  Corn stover yield was reduced in switchgrass treatments.  Grain yield did not differ between landscape positions, but stover dry matter yield and harvest moisture of both grain and stover differed between landscape positions.  The following year, switchgrass stand frequencies showed varieties were not different from one another within any given landscape position, but differences in stand frequency were observed in variety by landscape interactions.  Underseeding switchgrass into corn reduces yield of corn in establishment year and switchgrass stand frequency varies within field.  However, underseeding is an effective method to establish switchgrass while concurrently producing a marketable grain crop.