Soil Contamination and Elemental Concentrations of Forages in Relation to Grass Tetany
1983
Cherney, J. H. | Robinson, D. L. | Kappel, L. C. | Hembry, F. G. | Ingraham, R. H.
Relationships among soil contamination of forages, elemental concentrations in forages samples, and grass tetany are not clear. Our objectives were to determine the extent and seasonal variation of soil contamination on annual ryegrass (Lolium multiflorum Lam.) samples, and to relate the contamination to various indicators of grass tetany. Seasonal variation of soil ingestion by grazing beef cattle was also investigated. Field experiments were conducted on a Tensas silty clay soil (fine, montmorillonitic, thermic Vertic Ochraqualf). Highly significant positive correlations were obtained among AI, Fe, and Ti concentrations within forage and rumen content samples. Concentrations of these elements occurred in the same ratios as in digested soil. Soil contamination during peak periods averaged approximately 70 g/kg in forage samples and 95 g/kg in rumen content samples. A washing procedure was ineffective in removing all of the soil contamination from forage samples. Forage samples taken in areas protected from grazing animals showed no apparent excessive uptake of AI by the plants at any time during the grazing season. The amount of soil contamination on forage plants and the amount of soil ingested by grazing animals increased with increased grazing pressure, decreased forage production, and saturated surface soils. A rapid decline in forage Mg and Ca concentrations may have been a major factor in the Occurrence of grass tetany, but was not associated with highest levels of soil contamination.
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