• Blue grama response to Zn source and rates

      White, E. M. (Society for Range Management, 1991-01-01)
      Surface-applied zinc (Zn) in range with claypan soils could increase herbage production, but the Zn concentration could become toxic to the crown and roots of blue grama (Bouteloua grucilis). Metallic Zn, ZnCl2, and Zn chelate were applied in the greenhouse to the soil surface of pots with blue grama to determine the rate that would be toxic and the effect of Zn source on toxicity and herbage Zn content. Metallic Zn (dust, 30- and 40-mesh) was not toxic at rates below 0.40 g Zn kg soil-1, but Zn chelate was toxic and ZnCl2 at the 0.40 g Zn rate was toxic initially. After 2 years growth, salt was leached and herbage yields were not significantly different for different sources. Herbage Zn increased with increasing application up to about 0.9 g Zn kg-1. ZnCI2, applied to plants that were not Zn deficient, decreased growth; and half the plants died at rates of 2 g Zn kg soil-1. Herbage from the 2-gm rate had 7.4 g Zn kg-1. DTPA-extracted soil Zn increased with increasing applications but not at the same rate for different sources. Metallic Zn or ZnCl2, if applied at reasonable rates, is a satisfactory Zn source, but high rates of Zn chelate cause soil dispersion initially and should not be used on soil that disperses readily.
    • Effects of competition on spatial distribution of roots of blue grama

      Coffin, D. P.; Lauenroth, W. K. (Society for Range Management, 1991-01-01)
      The spatial distribution of roots of the perennial grass blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Grifftths] was evaluated under 2 competitive conditions. The radioistope 14C was used to label roots of blue grama plants growing with and without neighboring plants of the same lifeform. The majority of labeled blue grama roots (>75%) were found within 5 cm of the plant and within 10 cm of the soil surface. Labeled roots extended at least 30 cm from the edge of the plant and to depths of at least 90 cm. Root system morphology was insensitive to changes in competitive conditions. Based on our estimates of the depth and breadth of the root system of an average blue grama plant, roots associated with at least 4 other blue grama plants of average size and separated by average distances of 10 cm might occur within the volume of soil associated with roots of this plant. The distribution of total root biomass was not representative of the distribution of labeled roots, even when neighboring grasses were removed.