calcium and magnesium for body
some experimental work in Wisconsin varied the Ca:Mg ratio by adding gypsum (CaSO4) and/or Epsom salts (MgSO4) to two soils, Theresa silt loam (pH 6.8) and Plainfield loamy sand (pH 6.8). Phosphorus, potassium and sulfur were maintained at optimal levels throughout the experiment. Corn and alfalfa were grown as indicator crops.Table 2 shows the changes in alfalfa yield resulting from varying the Ca:Mg ratio. The results for corn, which yielded 100 and 140 bu/a in 1974 and 1975, respectively, are essentially the same as those for alfalfa.
These results are not surprising considering the way that calcium and magnesium are supplied to plants. These nutrients are moved to the roots in the water which the plant uses. A corn crop transpires between 250,000 and 400,000 gallons/a water during the growing season. By multiplying the amount of water used by the concentration of calcium and magnesium in the soil solution, you get an estimate of the amount of calcium and magnesium supplied to the root surface. For most Wisconsin soils, about 250 to 400 lb/a calcium and 100 to 160 lb/a magnesium are supplied to the root surface through transpired water. These values are much greater than the 26 to 40 lb/a calcium and 15 to 30 lb/a magnesium taken up by a 150 bu/a corn crop. Thus, the amounts of these nutrients taken up are determined by the selectivity of the roots. The remainder accumulates in the immediate vicinity of the roots.
recently, paper mill lime sludge (mainly CaCO3) has become available as a calcitic liming material. Using this material as a source of calcium to bring Ca:Mg ratios into “balance” on soils not requiring lime can result in severe nutrient deficiencies. Because of the presence of hydrated lime, Ca(OH)2, in paper mill lime sludge, soil pH values can quickly reach 9.0 when excessive quantities are applied. Under such conditions, trace elements as well as magnesium can become deficient. Gypsum (CaSO4) and calcitic limestone (CaCO3) often may be recommended to balance Ca:Mg ratios. However, continued application of gypsum or calcitic lime results in wide Ca:Mg ratios. This may give rise to magnesium-deficient forage which causes grass tetany in grazing animals. Once this stage is reached, it becomes very expensive to add sufficient magnesium to remedy the situation.