The use of weed technology in Palouse prairie remnants for management and restoration

Randall Elliott Stevens

Two studies were conducted to enhance management and restoration of prairie grasslands. First, utilizing a replacement series, interactions were compared between two prairie junegrass Koeleria macrantha (Ledeb.) Schult. biotypes from the Rocky Mountains (RM) and Eastern Washington (EW). Replacement series diagrams indicate RM height, basal area, and biomass was not affected when grown with EW, but EW growth was reduced when grown with RM. The EW biotype was reduced to 85%, 86%, and 71% of monoculture yield for height, basal area, and biomass, respectively. Only reductions in height and biomass were significant. Average relative yield (RY) values trend below the line RYRM = RYEW and indicate RM had a competitive advantage across all yield metrics. Relative crowding coefficient indicated RM had a greater competitive ability than EW for height, 1.125 to 0.889; basal area, 1.369 to 0.730; and biomass, 1.51 to 0.660, respectively. The second study evaluated effects of registered and non-registered herbicides to control grassy weeds for use in degraded Palouse prairie remnants. The herbicide treatments applied were chlorsulfuron at 30 g/ha, diclofop at 1120 g/ha, imazapic at 140 g/ha plus glyphosate at 190 g/ha, mesosulfuron at 190 g/ha, metribuzin at 600 g/ha, propoxycarbazone at 40 g/ha pyroxsulam at 230 g/ha, or sulfosulfuron at 50 g /ha, all applied with a nonionic surfactant at 0.5% v/v.. A nontreated control was included for comparison. Cover and richness data were recorded by species and divided into functional groups based on native status. Pyroxsulam, diclofop, and propoxycarbazone treatments had the greatest increase in species richness for total native plants over the nontreated, 5.0, 4.4, and 4.4 respectively (P > 0.0012). Pyroxsulam, sulfosulfuron, and imazapic plus glyphosate treatments reduced alien grass richness to 0.9, 0.8, and 0.8, respectively, contrasted with 1.8 for nontreated areas (P > 0.0032). Total native plant cover and native forbs cover increased most over nontreated plots with the application of pyroxsulam, 97% (P > 0.0363) and 88% (P > 0.0235), respectively. Imazapic plus glyphosate and sulfosulfuron significantly reduced alien grass cover over the nontreated 73% and 69% respectively, and were similar to pyroxsulam, chlorsulfuron, and diclofop (P < 0.0307).

The use of weed technology in Palouse prairie remnants for management and restoration

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