Temporal variability of rare earth elements in Ultisol soil under citrus plants

The objective of this study was to evaluate temporal variability of rare earth elements (REE) in soils of citrus agroecosystems. Instrumental neutron activation analysis was applied for measuring La, Ce, Nd, Sm, Eu, Tb, Yb, Lu and Sc. Sampling was performed in four citrus farms, with Valencia variety (Citrus sinensis L. Osbeck) grafted onto 'Rangpur' lime (Citrus limonia Osbeck), comprising both organic and conventional production systems in the Borborema region, Sao Paulo State, Brazil. There was slight temporal variability of some REE in different farms, however no clear positive or negative trend could be observed along the 3 years. (author)