Cadmium status of soils and plants from a long-term fertility experiment in southeast Norway

Abstract

To determine whether the use of phosphate fertilizer resulted in measurable cadmium accumulation in soils and crops harvested, soil and plant samples were collected from some selected treatments of a seventy year-old fertilizer experiment at Moystad, southeast Norway. Soil samples after extraction with Aqua Regia or 1M NH4NO3 and plant samples after digestion were analyzed for Cd. Cadmium balance based on fertilizer and atmospheric inputs and crop removal and leaching losses was worked out. Neither the total nor the available (NH4NO3-extractable) Cd in the soil was significantly affected by Cd added through fertilizer, though a tendency of higher Cd in soils from the plots receiving higher amounts of fertilizer was seen. The same trend was also observed for the Cd concentration in plants. Annual Cd input rates (fertilizer and atmosphere) varied from 1.20 to 2.57 g Cd ha-1 y-1 and the Cd removal (crops and leaching) rates varied from 1.16 to 1.79 g Cd ha-1 y-1. The balance calculations based on the seventy years data indicated Cd accumulation in the soil was <1 g Cd ha-1 y-1, but that increasing the doses of either commercial fertilizer or farm yard manure would likely result in increased accumulation of the element. This may have a negative impact because the available soil Cd content would be increased at a faster rate, resulting in increased plant uptake. Although Cd tended to accumulate as a result of P fertilization, the rate of increase was slow. The annual increase in the total Cd content of fertilized plots varied from 0.04 to 0.12% indicating that it may take from 800 to 2000 years, depending upon the fertilizer input, to accumulate Cd equivalent to that currently present in the soil.