Correlations between Light Rare Earth Elements in Soil and Navel Orange Tree System in Gannan Area

The total content of light rare earth elements (LREEs) in the soil of navel orange orchards of Gannan area is greater than that of heavy rare earth elements (HREEs). Appropriate content of LREE can not only promote the growth of navel oranges, and it is also conducive to human health. On the basis of exploring the correlations between the content of LREE in the soil of navel orange orchards of Gannan area and the contents of LREE in navel orange leaves and fruit, the influence mechanism of LREEs on the quality of navel oranges was revealed. In this study, with two Newhall navel orange orchards with different soil LREEs background levels in Xinfeng County as the research object, the changes in the content of LREE (lanthanum, La; cerium, Ce; praseodymium, Pr; neodymium, Nd) in leaves and fruit of navel orange at different growth stages were analyzed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), and the correlations between the content of LREE in the soil, navel orange leaves and navel orange fruit were studied. The results showed that the contents of the four kinds of LREEs in the soil ranked as Ce > La > Nd > Pr, and there were significant differences among them (P<0.01). Navel orange leaves and fruit have selective and heterogenic absorption for LREEs. At different growth stages, La showed the highest accumulation amount in the leaves and fruit of navel orange; and the content of LREE in the leaves of navel orange increased first and then decreased, while that in the fruit of navel orange showed continuous decrease. During the migration of LREEs from soil to leaves to fruit, the content of LREE decreased rapidly as the migration distance increased. The accumulation amount of LREE in navel orange was positively correlated with the content of LREE in the soil. The correlation between the content of LREE in the leaves and fruit of navel orange was greatest. Among the four kinds of LREEs, the correlation of La was greatest, followed by Ce, indicating that the accumulation amount of LREE in the navel orange body was affected by the element types.