Effect of Post-Emergence Weed Control on Grass Establishment in North-Central Colorado

Abstract

Winter-fallowing, planting grass into a clean seedbed, and controlling weeds during the seedling year, has been a particularly successful range-improvement practice in north-central Colorado. During the 3-year period (1964-1966), season-long hand weeding and spraying with 2,4-D when weeds were 6 to 12 inches high produced good stands in a year of average precipitation. However, neither spraying at later dates nor mowing the weeds at any date reduced competition from weeds sufficiently to produce a satisfactory grass stand. In a wet year, weed control in the seedling stand was not beneficial. In a year of extreme drouth, satisfactory stands were not obtained with any level of weed control. It was concluded that a technique of planting into a clean seedbed and spraying to control broadleaf weeds during the seedling year of the grasses offers the best chance for a successful seeding if wind erosion does not become a serious problem.