Establishing Warm-Season Grasses and Forbs Using Herbicides and Mowing

The objective of this study was to provide a preliminary assessment of the use of selected herbicides in establishing a diverse stand of prairie grasses and forbs. An upland and a lowland site in eastern Nebraska, consisting of well-drained, fine-silty clay, loess-derived soils, were seeded with 23 native prairie grass and forb species and subsequently mowed or treated at rates of 0.6, 1.1, 1.7, and 2.2 kg/ha with atrazine [6-chloro-Nethyl- N\u27 -(l-methylethyl)-l ,3,S-triazine-2,4-diamine] or 2,4-0 (2,4-dichlorophenoxyacetic acid). Treatments were applied at one and two-year intervals. Canopy cover in unreplicated treatment areas (12 x 30 m) was evaluated in ten randomly located plots (O.S x 1.0 m). In the lowland, four species of seeded forbs were established only in mulch-mowed plots. In the upland, the number of successfully established, seeded forb species was greatest in the control plot (9 species). While forb establishment was not maximized with herbicide use, such use did contribute to the rapid establishment of some warm-season grasses such as switchgrass (Panicum virgatum L.), 77% cover, and eastern gammagrass [Tripsacum dactyloides (L.) L.], 21 % cover, in the lowland and blue gram a [Bouteloua gracilis (H.B.K.) Lag. ex Griffiths], 11 % cover with 2,4-0, and little bluestem (Andropogon scoparius Michx.), 60% cover with atrazine. Comparisons of fall total standing crop biomass 0.11 kg/m2 for lowlands and 0.47 kg/ m2 for uplands) and seedling establishment suggested that high standing crop biomass, regardless of species composition, was likely to affect the establishment of a diverse stand of grasses and forbs. Where stand diversity is the primary objective, methods that prevent high biomass accumulations, particularly the first year or two, will be most successful