Magyar Marianna

In a pot experiment five phosphate rocks, originated from Algeria, Florida, North Carolina, Senegal and Morocco, Hyperphosphate and single superphosphate (SSP), as well as SSP+CaCO3 were applied in 0-100-400-1600 mg P2O5 kg-1 rates, with particle size of <160µm, on a strongly acidic sandy soil with very low available P content. Red clover plants were grown in the pots in greenhouse conditions. Shoot and root growth, P uptake and P acquisition efficiency were strongly depressed by the increasing rate of applied P fertilizers above a critical rate, which was around 100 mg P2O5 kg-1 of soil for red clover for the phosphate rocks and soil conditions of the experiment. Both the type of applied P fertilizer and its rate of application markedly affected the P acquisition efficiency of the red clover crops. Senegal treatment gave the lowest plant phosphorus uptake and the highest Cd uptake, which was more than three times higher, than Cd uptake from any other P source. The bioavailability of Cd increased with increasing P rates, except of the more buffered SSP+CaCO3 treatment.