The Impacts of Short-Term Irrigation and Seeding Grass Cover Crops on the Establishment of Native Shrubs on Abandodned Farmlands in the Great Basin.

Irrigated farmlands throughout the arid western United States are increasingly being removed from active agricultural production due to a loss of irrigation water. Typically, the irrigation water is purchased and transferred to other uses.  Long lived, perennial, drought tolerant shrubs were the dominant vegetative component of much of these lands before they were converted to farmland. However, the natural restoration of shrubs on these lands is slow to non-existent due to low amounts of precipitation, highly competitive, invasive weeds and wind erosion. Lacking restoration, these lands become a source of weeds and severe wind erosion for surrounding farmlands remaining in production. The purpose of this project was to evaluate typical crop production schemes including short-term irrigation and the use of native grasses as a cover crop to facilitate the establishment of several native shrubs on these abandoned farmlands. Using a blocked, split-plot design, we determined the impacts of short term irrigation, and seeding of five native grasses on the establishment of four native shrub species over a five year period on two previously irrigated sites in the Great Basin of Nevada. The combination of irrigation and seeded grass species was associated with significantly lower wind erosion, weed density and weed biomass. Three years after irrigation ended, seeded grasses remained significantly more abundant in formally irrigated than non-irrigated control plots and also had less bare ground, annual plant cover and weed biomass. Although seeded grasses reduced erosion and weed invasion they failed to facilitate native shrub establishment. Shrub cover and density were highest in plots that had been drill seeded and irrigated but lacked significant perennial grass cover.