Blue Grama Herbage Yield in Relation to Available Soil and Herbage Zinc Contents
1991
White, E. M. | Gartner, F. R.
Blue grama (Bouteloua gracilis [HBK] Lag. ex Steud.) growth on weathered claypan soils can be increased by Zn fertilization. Relationships between herbage yield and Zn content and soil dimethylenetriaminepentaacetic acid (DTPA)-extracted Zn need to be established so that areas needing Zn can be identified more accurately. The objectives are to determine the soil DTPA-Zn and herbage-Zn contents needed by blue grama. Zinc-deficient claypan soils and glacial-till-derived soils with adequate Zn were used to grow blue grama that was unfertilized or fertilized with N, NPK, or NPK plus minor elements (ME). The DTPA-extracted soil Zn, Cu, Mn, and Fe were determined to establish the soil Zn levels needed and the possible interaction of other cationic ME on Zn. For the same reason, the ash, Zn, Mg, Co, Mn, Fe, and P contents were determined for blue grama herbage grown in the greenhouse on a Zn-deficient claypan soil treated with eight Hoagland-type solutions. Solution 1 contained NPK; 2, NPK + B; 3, NPK + B + Zn, and additively in succession Mn, Fe, Cu, Mo, and Co. Possible changes in Zn content with increasing herbage age were studied with two groups of plants harvested after different-length, but overlapping, growth periods. The herbage harvested was analyzed for Zn, P, and N. The DTPA-extracted soil Zn must be about 2 mg kg⁻¹ for growth, although NPK fertilization may increase growth and decrease extractable Zn to a lower amount, at least temporarily. For vigorous plants, young herbage has at least 11 to 13 mg Zn kg⁻¹. Older herbage has less Zn, particularly if Zn is limiting growth after NPK has been added. The DTPA-extractable soil Zn contents were not related to the extracted Fe, Cu, or Mn contents. Plant Zn and Mg contents were correlated, but not to Co, Mn, Fe, or P contents.
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