Rock phosphates and P fertilizers as sources of U contamination in agricultural soils

U concentrations were analyzed in a set of mineral fertilizers with and without P and compared to U concentrations in various organic fertilizers. Mean concentrations between 6 and 149 mg/kg U were found in P containing mineral fertilizers, while mean concentrations in mineral fertilizers without P were below 1.3 mg/kg U. Mean U concentrations in farmyard manures did not exceed 2.6 mg/kg U. As a consequence, an average P dressing of 22 kg/ha P would charge the soil with up to 17-61 g/ha U when added as mineral fertilizer but less than 10 g/ha when given as farmyard manure or slurry. Expected U uptake by crops is less than 1 g/ha U.