Although higher silver levels in plants occur in regions of silver mineralization, there is no correlation between soil levels and plant levels of silver (Boyle 1968). The ratio of silver in plants to silver in soil has been given as 1:1.5 but one should use such a ratio with caution because the range is very wide, up to 1600 times (Lisk 1972, Horovitz et al. 1974).
Concentrations of 728 to 1015 mg silver/kg ash were found in roots of the experimental crops, corn, sugar beet and kentucky blue grass, grown on soils containing 26 mg silver/kg dry-weight. The silver was applied as AgNO3. The ratio of silver in roots to that in soil was 28:1 to 39:1. If the soil was treated with AgI to contain 12 mg silver/kg dry-weight, the silver level in the roots was 43 to 176 mg/kg for a ratio of silver in roots to silver in soil of 4:1 to 15:1. In control soils with 90 µg silver/kg dry-weight, the silver levels in the roots were 1.2 to 3.4 mg/kg dry weight for a ratio of 13:1 to 38:1. The corresponding ratios for stems and leaves of control crops were similar, 13:1 to 17:1, but the ratios in the treated plants were smaller from 0.5:1 for AgI to 7:1 with AgNO3. Silver thus concentrates in the roots and the silver in AgNO3 is more available than the silver in AgI (Teller and Klein 1973).