• Impacts of Off-Road Vehicles on Infiltration and Sediment Production of Two Desert Soils

      Eckert, R. E.; Wood, M. K.; Blackburn, W. H.; Peterson, F. F. (Society for Range Management, 1979-09-01)
      Impacts of motorcycle and 4-wheel drive truck traffic on infiltration rate and sediment production were evaluated on two desert soils. Infiltration was similar for both soils; however, more sediment was produced from a surface with exposed mineral soil than from a gravel-mulched surface. Infiltration was 3 to 13 times greater on the coppice soil beneath shrubs than on interspace soil between shrubs, but sedimentation was 10 to 20 times greater on interspace soil. Infiltration was less and sediment yield was greater after soil was disturbed by vehicular traffic, and after reformation of the surface crust, particularly on interspace soil. High sediment production from interspace soil was attributed to reduced infiltration after 10 minutes. The soil then became saturated and unstable, was dispersed by raindrop impact, and particles were carried in runoff water for the remaining 20 minutes of the test period. Coppice soil had a high infiltration rate for the entire test period and did not become saturated. In addition, the high organic matter and aggregate stability of coppice soil prevented soil movement, though some runoff occurred.
    • Renovation of Sparse Stands of Crested Wheatgrass

      Eckert, R. E. (Society for Range Management, 1979-09-01)
      Atrazine at 0.56 kg/ha and simazine at 1.12 kg/ha were evaluated for renovating sparse stands (0.9 to 1.5 m between plants) of resident crested wheatgrass. The study was repeated for 3 years for both weed control and seeding of crested wheatgrass. Both herbicides reduced yield and reproductive potential of downy brome and tumble mustard in the fallow year. Neither herbicide significantly damaged the vegetative or reproductive parts of resident crested wheatgrass plants. Atrazine residues in the soil in the fall of the fallow year and spring of the seeding year were below the toxic level for crested wheatgrass seedling. Simazine residues were above the toxic level. Both herbicides increased seed production of resident crested wheatgrass plants and neither adversely affected seed test weight and germination, or root and shoot growth of seedlings from seed of these plants. Weed competition during the seedling year was reduced by herbicide treatment. Density of crested wheatgrass seedlings and established plants was greatest on treated plots in 2 of 3 years. Based on low triazine residues and increased crude protein, resident crested wheatgrass on treated areas would be excellent forage during the fallow year. High levels of NO3- N, trans-aconitate, and K, but low Mg suggest that grass tetany could be a problem if lush herbage on treated areas was grazed during the spring period.