Long-term impacts of different fertiliser scenarios on metal leaching and metal uptake in Slovakian and Hungarian agricultural soils

This paper evaluates the possible long-term (50 years) impact of the acidification of agricultural soils, due to stopping with liming, on dissolved cadmium (Cd) and zinc (Zn) concentrations and contents in crop (wheat and maize) for representative Slovakian and Hungarian agricultural soils. The predictions were made with the soil acidification model SMART, adapted for agricultural soils, combined with transfer functions for heavy metals describing relationships between: (i) total and reactive heavy metal contents in the soil solid phase, (ii) dissolved metal concentrations and reactive soil metal contents and (iii) total heavy metal contents in crops and in soil, while accounting for the impact of organic matter and clay content and soil pH. Initial pH values in the Slovakian and Hungarian non-calcareous soils varied mostly between 4.5 and 5.5. Simulated changes in soil pH are dependent on the soil type and time period but in general a pH drop of 0.5-1.0 is predicted in a 50-year period, the largest changes taking place in the first 20 years. Adverse affects on soil life, too strong for Zn, can be caused by elevated dissolved Zn concentrations. In Slovakia, the predicted percentage of plots exceeding a critical Zn concentration of 250 mg/ cubic m increases from less than 10% at the start of the simulation to 40% after 50 years. The percentage of plots with a dissolved Cd concentration above a critical level of 2 mg/ cubic m increases from approximately 10 to 20% in 50 years. Adverse affects on crops are due to elevated Cd contents in wheat, whereas Zn is not a problem. Results show that the predicted percentage of plots exceeding a critical Cd content of 0.1 mg/kg is about 90% at the beginning in Slovakia and this percentage will slightly increase as a result of acidification. In Hungary, Cd contents are already near 0.3 mg/kg at the start of the simulation. These high Cd contents are most likely due to the low humus and clay contents of the studied 10 soils. The effects of an alternative fertiliser scenario on the pH and Cd contents in soil appeared to be limited.