REVEGETATING LEAFY SPURGE (EUPHORBIA ESULA)-INFESTED RANGELAND WITH NATIVE TALLGRASSES

Degradation of great Plains rangelands can be linked to past managemen t practices that reduced native species diversity and accelerated esta blishment and expansion of exotic weeds and less desirable native spec ies. Leafy spurge is an exotic perennial weed that infests more than 1 million ha in the northern Great Plains and reduces rangeland carryin g capacity by competing with desirable forages and causing infested ar eas to be undesirable to cattle and wildlife. Research was conducted t o determine the feasibility of using herbicides to suppress leafy spur ge and other resident vegetation, which facilitated planting and estab lishment of native tallgrasses, Four experiments were conducted where 0.28, 0.56, and 0.84 kg ai/ha imazapyr and 0.1 kg ai/ha sulfometuron w ere applied alone and in combination and 0.84 kg ai/ha glyphosate was applieci to leafy spurge-infested range sites in fall 1991 near Ainswo rth, NE, and in fall 1991, 1992, and 1993 near Ansley, NE. Research ar eas were burned about 200 d after herbicide application to reduce plan t residue. Monoculture stands of big bluestem and switchgrass were the n no-till planted in each experiment and indiangrass was no-till plant ed in experiments initiated at Ansley in 1992 and 1993. Yields of the planted grasses, leafy spurge, and other vegetation were measured in A ugust at each location starting the year after planting. Imazapyr was an essential component of treatments applied before planting to facili tate establishment of highly productive stands of the tallgrasses. Gen erally, yields were maximized by fall treatments of 0.28 kg/ha imazapy r + 0.1 kg/ha sulfometuron for big bluestem, 0.84 kg/ha imazapyr for i ndiangrass, and 0.84 kg/ha imazapyr + 0.1 kg/ha sulfometuron for switc hgrass. Yields of the planted grasses were frequently four times great er where these herbicides were applied compared to where glyphosate or no herbicide were applied. Leafy spurge yields were usually reduced i n areas where tallgrass yields were greatest. The sequential combinati on of suppressing vegetation with fall-applied herbicides, burning sta nding dead plant residue, then no-till planting desirable native tallg rasses in the spring increased productivity of these leafy spurge-infe sted range sites.