Cerium (Ce) and Lanthanum (La) promoted plant growth and mycorrhizal colonization of maize in tropical soil

Rare earth elements, such as lanthanum (La) and cerium (Ce), have been employed as agricultural inputs in some countries to enhance yield and crop quality.Benefits of arbuscular mycorrhizal fungi (AMF) inoculation for maize are also well established, but effects of inoculation in coapplication with La and Ce are largely unknown.In the current study, the effects of La and Ce application were evaluated in two separate experiments, in soil and seed treatments.Both studies were performed using a completely randomized design in a 6 x 2 factorial scheme, with four replicates.Plants were exposed to the following concentrations (mg dm -3 as soil application): La -0, 20, 40, 60, 80, and 100; and Ce -0, 25, 50, 75, 100, and 125; and (mg L -1 as seed application) 0, 6, 12, 18, 24, and 30 for both elements, in presence and absence of AMF inoculations.Both elements enhanced maize growth, mainly at 60 and 40 mg dm -3 doses for soil application, and 15 and 10 mg L -1 doses for seed treatment, for La and Ce respectively.Moreover, at lower doses, both elements stimulated AMF colonization.A synergistic relationship was also observed between AMF, Ce and La on growth of maize.Results provided relevant information on Ce and La effects on maize growth in tropical environments, suggesting that application of these rare earth elements in soils containing AMF propagules is promising to improve crop production in tropical soils.