Soil Oxygen and Temperature Effect on Tetany Potential of Three Annual Forage Species
1977
Elkins, Charles B. | Hoveland, Carl S.
Grass tetany, a metabolic disorder of cattle on pasture, has often been related to low Mg and high K levels, and high K/(Ca-+-Mg) equivalent ratios in forages. These forage mineral imbalances often occur during wet periods when soil O3 may be low. The effect of 2, 4, 8, 16, and 21% soil air O, on Ca, Mg, and K contents of rye (Secale cereale L.), ryegrass (Lolium multiflorum Lam.), and arrowleaf clover (Trifolium vesiculosum Savi) was studied in the growth chamber at 22 C day air temperatures and 12 or 16 C night temperatures. Increasing soil O₂, had little effect on Ca or Mg content of rye forage but increased K from 2 to 5%, and increased the K/(Ca-+-Mg) ratio to over 4. Uptake of K, Ca, and Mg was generally lower at 12 than at 16 C. Ryegrass forage, grown at increasing soil air O₂, had higher K, Ca, and Mg contents. Concentrations of K, Ca, and M in ryegrass were lower at 12 than at 16 C. Magnesium levels at 2 to 16% soil O2 were below the critical level of 0.2% at 12 C air temperature. Soil O₂ had little effect on the composition of arrowleaf clover forage, except for a small increase in K. These results indicated that ryegrass forages, grown on poorly-drained soil would likely be more tetany-prone th.in that grown on well-drained soil. However, rye forage would be more tetany-prone when grown on well-drained soil. The high Mg levels of arrowleaf clover showed its value in balancing tetany-prone grass forage when it is maintained in a pasture.
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