Assessing Essential and Toxic Elements in Rabbit Manure and Rock Phosphate Fertilizers Using Nuclear Techniques: A Contribution to Managing Nutrient Resources for Improved Small-Stock/ Crop Integration

Industrial phosphate fertilizers are currently the major source of phosphorus for agricultural activities. Many authors maintain that the addition of organic amendments such as manure can ameliorate disturbed soils by improving some characteristics including the available phosphorus (P) in the soil. Furthermore, these products may provide macro elements such as nitrogen (N) and calcium, essential microelements and toxic contaminants. This study deals with uranium content in rabbit manure and six most common phosphates applied in Brazil. Results are compared with values from four other phosphates mined around the world. The nuclear analytical method applied was the delayed neutron technique (DNT) which is a highly precise, affordable, fast (short turnaround) instrumental technique. Three phosphates had uranium content above 145 μg/g, while rabbit manure, a high N, P and potassium (K) organic amendment contains only 2.7 μg/g of uranium. Additionally, neutron activation analysis, a sensitive multi-elemental nuclear analytical technique was used to identify essential and toxic elements in the rabbit manure and a rock phosphate, one of most inexpensive and popular fertilizers available in the Brazilian market. Results for arsenic, barium, bromine, cobalt, chromium, fluorine, iron, sodium, thallium, zinc and K are presented in order to help decision-making concerning strategies for fertilizersoil- crop management that are both agronomically and environmentally viable. High contents of some toxic elements demonstrate the need to evaluate deposition of contaminants released by fertilizers on farmland, the wider environment and the entire food chain. (author)