Blue grama response to Zn source and rates

Abstract

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.