Production and Competition of Crested Wheatgrass‐Native Grass Mixtures1

Abstract

AbstractMining in the Northern Great Plains is resulting in the disturbance of large acreages of rangeland which requires revegetation to stabilize the soil resource and return it to productivity. The competition of ‘Nordan’ crested wheatgrass [Agropyron desertorum (Fisch.) Schult.] with four individual native grass species and with a mixture of the four species was evaluated in the field at Cheyenne, Wyoming. This study was initiated to determine if crested wheatgrass, an easily established introduced species, can be seeded with more difficult to establish native grasses and result in a diverse community. Crested wheatgrass was seeded with slender wheatgrass [A. trachycaulum (Link) Malte], thickspike wheatgrass [A. dasystachyum (Hook.) Scribn.], western wheatgrass (A. smithii Rybd.), and green needlegrass (Stipa viridula Trin.) or with a mixture of these four native species in the fall of 1976 on an Archerson fine, sandy, clay loam (Aridic Arguistol). Crested wheatgrass comprised 25% of the seed mixture in all treatments. In 1977, 69.5, 42.5, 22.5, and 22.6% of the total production was slender, thickspike, and western wheatgrass and green needlegrass, respectively. In 1980, production of slender, thickspike, and western wheatgrass and green needlegrass was 2.6, 15.5, 15.5 and 36% of the seeded species production, respectively. This decrease in percentage of production of the native wheatgrass species was the result of a large increase in crested wheatgrass production.When crested wheatgrass was seeded with the mixture of all four native species, the 1977, 1978, 1979, and 1980 production of the native species represented 62.4, 31.2, 21.3, and 4.3% of the seeded species production, respectively. The major decline in percentage of production contributed by the native species in 1978 was largely due to the loss of slender wheatgrass. In 1977, slender wheatgrass represented 76.8% of the production of the native species, however, it declined to 18.2% in 1978. By 1980, all of the native species had declined to the point that the mixture was nearly a pure stand of crested wheatgrass.It appears that green needlegrass when seeded alone with crested wheatgrass is able to successfully compete and make substantial growth. However, inclusion of other native species in the mixture with green needlegrass resulted in a greater competition among the native species, which caused a decline in green needlegrass production. Seeding crested wheatgrass with these native species or with a mixture of these native species is not recommended if you desire a major portion of the production to be native species. Although crested wheatgrass represented 25% of the seed mixture in all treatments, after 4 years it represented at least 64% of the production.