Seeding Rate and Weed Control Effects on Indiangrass Growth and Development and Forage Yield.

Development of perennial grasses for cellulosic biomass, forages, and conservation practices depends on rapid production of high biomass yields and forage quality. While there are studies with information on other warm-season perennial grasses, there is little data available for establishing indiangrass [Sorghastrum nutans (L.) Nash]. The primary objective of this study was to evaluate the seeding rate effects on dry matter (DM) yield and establishment year tiller development of ‘Oto and ‘NE 54’ indiangrass in a study conducted near Mead, NE from 2003 to 2006. The cultivars were seeded at 100, 200, 300, 400, and 500 PLS m^-2 with either mowing or Plateau [(±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid]) as a method of weed control. Developmental stages were assessed by staging tillers clipped from a 0.09 m² frame and tillers were counted to measure tiller density. Biomass was harvested at the end of each growing season to evaluate DM yield. Tiller number during the establishment year was nearly always greater for Oto than NE 54 across all seeding rates. For NE 54, during the establishment year, tiller number was similar for the 100, 200, 300, and the 500 PLS m^-2 seeding rates, with the 400 PLS m^-2 seeding rate having approximately 40% more tillers than the 100 PLS m^-2 seeding rate. Dry matter yield was greater for Oto than NE 54 across all seeding rates. In the weed control treatments, DM yield was 20% greater for Plateau compared with mowing for both cultivars in the first year and second year after establishment. Interestingly, seeding rates greater than 200 PLS m^-2 did not result in greater DM yield after 4 yr. Although seeding rate did not increase DM yield, the importance of early weed management on indiangrass at low seeding rates was clearly demonstrated during early stand production.