Balance of heavy metals [Cd, Ni, Pb] in static fertiliser experiments on grasslands

On the basis of results obtained in 2 static experiments conducted on light and heavy soils with differentiated mineral fertilisation, an approximate balance of Cd, Ni and Pb was determined over 20 years of investigations. The experiments included 3 levels of fertilisers and the control plot. Ammonium nitrate, single or triple superhosphate and potassium salt were used for the treatments. Average amounts ofheavy metals introduced with the fertilisers in both experiments over twenty years were as follows: 37-110 g Cd, 63-195 g Ni and 62-202 g Pb ha-1. The balance ofheavy metals over twenty years assumed different values depending on the fertilisation level and soil conditions. However, irrespective of those factors, the balance assumes a negative value. The effect of nitrogen doses on the balance was slight and depended on the site trophicity. On the other hand, increasing doses of phosphorus and potassium treatment decreased the value of the negative balance difference of cadmium and, to a lesser degree, of nickel, but increased the lead balance.