Cation and anion relationships in plants with special reference to seasonal variation in the mineral content of alfalfa
1949
Wallace, A. | Toth, S.J. | Bear, F.E.
A survey of the literature on plant composition and data obtained from greenhouse and field studies have indicated that: 1. Plants with high cation summation values tend to have high anion summation values and vice versa. This relation holds with plants of different species and also within species. 2. In terms of equivalents, N is the most dominant of the anions in plants and comprises approximately 70 to 90% of the total anion summation values. 3. Variations in cation and anion summation values of successive harvests of forage crops are explained on basis of the operation of a carbohydrate dilution factor. During periods of rapid formation of carbohydrates, the cation and anion content per unit weight of tissue is "diluted," resulting in a lower cation and anion summation value. 4. Successive harvests of alfalfa, grown in the field under comparable conditions, had a constant cation-anion ratio. 5. The second cutting of three successive harvests of field-grown alfalfa had the lowest cation and anion content. The reduction in cation and anion contents of the harvests was proportional to each other and is believed to be related to operation of a carbohydrate dilution factor. 6. The importance of the seasonal variation of the mineral nutrient content of alfalfa to animal feeding is indicated by the fact that cuttings of low cation and anion content contain less minerals and protein per unit weight than harvests of high cation and anion content.
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