Weed Control and Seeding Rate Impacts on Indiangrass Establishment and Persistence.

Indiangrass [Sorghastrum nutans (L.) Nash] use has been historically limited by lack of seedling tolerance to herbicides. Herbicides and mowing are two common weed control methods used in perennial grass establishment. Previously, weed competition has reduced indiangrass seedlings and forage yield by 33%. The primary objective of this study was to evaluate two weed control methods and seeding rate on establishment and persistence of ‘Oto and ‘NE 54’ indiangrass. 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 in a study conducted near Mead, NE from 2003 to 2007. Stand frequency was determined using a 75 cm x 75 cm frequency grid. During the first two years post-seeding, stand frequency was lowest for the 100 PLS m^-2 seeding rate for both cultivars. Stand frequency increased with increasing seeding rate for both cultivars, although Oto was more variable across years than NE 54. All seeding rates had greater than 75% stand frequency with the exception of the 100 PLS m^-2 seeding rate. For Oto after the first year, stand frequency was greater for the Plateau treatment. Stand frequency was similar for both weed control treatments after the second year of the study. After 5-years, there were no stand frequency differences regardless of weed control method. With Plateau application, seeding rates as low as 200 PLS m^-2 can result in functional, persistent stands with a greater stand frequency than mowing. This will likely increase interest in establishing indiangrass for multifunctional uses such as pasture, bioenergy, and conservation.