Restoring tallgrass prairie species mixtures on leafy spurge-infested rangeland

Leafy spurge (Euphorbia esula L.) reduces northern Great Plains rangeland c arrying capacity. Treatment strategies were evaluated that suppressed leafy spurge and facilitated establishment of mixtures of native grasses and leg umes on range sites near Mason City and Tilden, Nebr. Glyphosate at 1,600 g a.i, (active ingredient) ha(-1) was applied with or without imazapic at 14 0 or 210 g a.i. ha(-1) in October 1995. In April 1996, standing crop was bu rned or mowed. Mixtures of native grasses [big: bluestem (Andropogon gerard ii Vitman), indiangrass (Sorghastrum nutans (L.) Nash), switchgrass (Panicu m virgatum L.), little bluestem (Schizachyrium scoparium (Michx.) Nash), an d sideoats grama (Bouteloua curtiplendula (Michx.) Torr.)] were then plante d with or without native legumes [leadplant (Amorpha canescens (Nutt.) Purs h), Illinois bundleflower (Desmanthus illinoensis (Michx,) MacM.), and purp le prairieclover (Petalostemum purpureum (Vent,) Rybd.)] at 330 pls m(-2) i nto a non-tilled seedbed. Imazapic was applied at 70 g a.i. ha(-1) in June 1996 to half the plots that had been treated with imazapic in October 1995, Frequency, dry matter yield, and leaf spurge density were measured 14 to 1 6 months after planting. Leafy spurge density and yield were least, and fre quencies and yields of the planted grasses usually were greatest where imaz apic had been applied with glyphosate in October 1995, Purple prairieclover was the only planted legume to persist 14 months after planting, and yield s were greatest where imazapic was applied with glyphosate. Imazapic applie d in June 1996 usually did not improve planted species yields or leafy spur ge control. Total vegetation yields were greater where imazapic was applied with glyphosate at both sites and where native species were seeded at Maso n City. Vegetation suppression with fall-applied herbicides and removal of standing crop enabled successful establishment of desirable species, increa sed forage yields, and suppressed leafy spurge.