CONTRIBUTION DE L'ACIDE FULVIQUE ET DES COMPLEXES FULVO-METALLIQUES A LA NUTRITION MINERALE DES PLANTES

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Abstract
Fulvic acid and fulvo-metallic complexes were studied with respect to the influence of the former on the absorption and the utilization of nutrients by plants, and the latter with respect to their value as sources of P and Fe. Corn was grown in silicic sand and water culture, and alfalfa and bromegrass in soil. Treatments consisted in varying the P and Fe sources of the growth medium in the presence and absence of fulvic acid. Fulvo-phosphates (fulvic acid-iron-phosphate) were shown to be a poor source of P for plant growth, although they supplied considerable amounts of Fe. The complexing of Fe and P by fulvic acid in the growth medium resulted in a reduction of the P availability. An important interaction was observed, involving fulvic acid, Mn and P, which resulted in increased dry matter yields, and in a better utilization of phosphorus by the plants. Fulvic acid promoted plant growth, but this appeared to be due to an ion transferring effect at root level or to a direct physiological effect, rather than to reactions in the culture medium.