Restoring Native Plant Species in Crested Wheatgrass Rangelands Using Glyphosate and No-Till Reseeding

Abstract

The objectives of this study were to evaluate the effects of spring application of glyphosate (1.1 kg/ha) on 1) crested wheatgrass (Agropyron cristatum (L.) Gaertn) phytomass, 2) seedling establishment of native grasses and forbs using no-till reseeding and 3) non-target plant species responses. Field trials were conducted at five sites in central and eastern Montana in 2002 and 2003. Each site contained sixteen 36x36 m plots to test four treatments. The treatments included control, glyphosate only, glyphosate plus cool season plants no-till seeded in the fall, and glyphosate plus spring no-till seeding of cool season plants in 2002. In 2003, one half of the plots were sprayed a second time with glyphosate to control crested wheatgrass growth. Five 0.25 m2 quadrats per plot sampled in August were used to estimate crested wheatgrass, seeding and non-target phytomass. Split plot error was the testing term for glyphosate treatment differences, and the whole plot error was the testing term for planting treatments. Data that was not normally distributed was rank-transformed. Data was analyzed by site due to site by treatment interactions. Application of glyphosate for two consecutive years reduced crested wheatgrass phytomass 91% compared to controls. Application for one year reduced phytomass 56% across all sites but two sites showed no reduction in phytomass one year after application. No-till seeding failed on four of five sites due to lack of adequate moisture and did not influence seedling phytomass a year after planting. Non-target plant species biomass was increased by glyphosate application on four of five sites. Application of glyphosate did not increase seedling establishment planted under low moisture conditions, but it increased biomass of non-seeded plants.