The faint yellow haze coloring many early summer pastures in Nebraska may look pretty to passers-by, but it's a disheartening sight to landowners. It signals an infestation of the dreaded weed, leafy spurge.
Where there's leafy spurge, accompanying plants are likely to be an unproductive mix of Kentucky bluegrass and bromegrass, with other pesky broadleaf weeds thrown in.
This mix is poor grazing, produces low hay yields without fertilization, and the leafy spurge is tough to control.
Range scientists call this mix a "degraded" pasture; producers call it a big headache.
Bob Masters, USDA-Agricultural Research Service rangeland scientist at NU, sees it as an opportunity.
"We're in the process of developing a strategy to reclaim these pastures that will provide producers with a higher quality forage and also meet the needs of people who are interested in prairie restoration," Masters said.
Masters combines herbicide application, prescribed burning and planting native warm season grasses to defeat leafy spurge and produce high quality pasture.
"If you use several tools in combination you can move pastures more rapidly back toward native species," he said.
Native tallgrass prairie species, such as big and little bluestem, Indiangrass and switchgrass, originally inhabited eastern and central Nebraska. These grasses and their broadleaf companions, wildflowers and legumes, are predominantly warm season species that grow mainly from mid-May to mid-September.
A long process caused native pastures to degrade, Masters said. Over-grazing is the prime culprit, causing a shift toward less-productive cool season grasses like Kentucky bluegrass.
Wildfires, which once kept cool season species in check, all but disappeared when the prairies were settled.
Many pastures also were converted to cropland, then back to pasture, which let weedy species like leafy spurge move in.
"It takes time to get a natural system back in shape," Masters said, but his reclamation strategy shows promise for creating a lush native grass stand and high hay yields as early as the second season after planting.
In 1992 Masters began testing his strategy on degraded rangeland near Ansley where the predominant plant species were Kentucky bluegrass, smooth bromegrass and leafy spurge. In late September, when these plants were still actively growing, he sprayed plots with Arsenal and Oust herbicides to kill existing vegetation. In later tests, he switched to less costly Roundup and Plateau herbicides.
"Plateau will probably be labeled for this use no later than 1999," Masters said. "It is excellent for controlling cool season grasses and gives residual control through the next season."
The following spring Masters burned off the plant residue. In early May he seeded big bluestem, Indiangrass and switchgrass directly into the sod.
"It's essential to minimize tillage, because it's expensive and opens up the soil to more weeds," Masters said.
At the end of the growing season Masters calculated how much plot vegetation was composed of each grass species and measured hay yields.
Three years after planting, thick stands of big bluestem and switchgrass cover the rangeland.
"We're harvesting 5,000 pounds of dry matter per acre, compared to 1,200 pounds from the Kentucky bluegrass-leafy spurge pasture," Masters said. "We not only have more forage, it's better quality."
Establishing such a pasture initially is costly. Switchgrass sells for $2.50 to $3 per pound of pure live seed, and big bluestem costs up to $8 per pound. The total cost for a solid stand of big bluestem runs about $150 per acre.
"But by the first year after planting we were able to recoup about $120 per acre from hay yields," Masters said.
This research was supported in part by the Sampson Endowment in the NU Foundation.
--Monica Manton Norby