Establishment of sand bluestem with the aid of pre‐emergence‐applied herbicides

Controlling competition with weeds is critical to successful native perennial grass establishment. Our objective was to determine the potential of several pre‐emergence‐applied herbicides to control annual weeds and aid sand bluestem (Andropogon hallii Hack.) establishment. Sand bluestem was seeded at one site in two adjacent areas during the end of March 2002 and 2003 in Woodward, OK, and at one site during the end of March 2004 near Fort Supply, OK, at 14.4 lb pure live seed acre−1 each year. Herbicides were applied within a few days of seeding and were watered in with ∼0.75 inch irrigation water within 1 wk of application at the Woodward sites whereas no irrigation water was supplied at the site near Fort Supply. Response variables measured were sand bluestem stand frequency 13 mo after seeding and forage production 16 mo after seeding. Thiazopyr prevented germination of sand bluestem in all plots, and atrazine + acetochlor produced stands significantly lower than the untreated controls in both locations. Imazapic produced stands of sand bluestem that were significantly greater than the untreated plots in both locations. Forage production of sand bluestem was significantly greater when imazapic was applied within 7 d after seeding than in untreated plots at both locations. Over all three sites, sand bluestem forage production averaged 3,202 lb acre−1 where imazapic was applied compared with only 1,663 lb acre−1 in plots not treated with herbicide. Sand bluestem forage production was consistently increased where imazapic was applied shortly after planting. Core Ideas Establishing native warm‐season grasses are a critical bottleneck for their adoption. Pre‐emergence‐applied herbicides can improve stand establishment of sand bluestem. Application of imazapic improved stand establishment and forage production.