Objective:

To evaluate the effect of simple and combined biofertilization of Azospirillum brasilense and Rhizoglomus irregulare on the nutritional status and biomass yield of Tithonia diversifolia (Hemsl.).

Materials and Methods:

In a field experiment four treatments were studied, made up by the simple and combined inoculation of A. brasilense and R. irregulare plus a non-inoculated control, in a Latin square design. The inoculant with R. irregulare, with a concentration of 30 spores g-1, was applied through the use of Canavalia ensiformis (L.) DC as preceding crop and a way for the reproduction of mycorrhizal fungi in the soil. A. brasilense, with a concentration of 109 CFU mL-1, was administered at a rate of 20 L ha-1, 15 days after planting. The frequency and intensity of the mycorhizal colonization, the concentrations of NPK in the biomass of the aerial part and dry matter yields, were evaluated.

Results:

R. irregulare increased the frequency and intensity of mycorrhizal colonization, as well as the number of spores in the rhizosphere. Nevertheless, the highest effects were reached when it was applied jointly with A. brasilense. The biofertilizers separately increased the nitrogen concentrations in the aerial biomass and the dry matter yields, but the highest values of these variables, as well as the highest efficiency of biofertilization, were obtained with the joint application of both. The effect of biofertilization remained during the year in which the experiment was conducted.

Conclusions:

The simple inoculation with A. brasilense and R. irregulare improves the nitrogen nutrition and biomass yields of T. diversifolia. With the joint application of both biofertilizers, higher effectiveness of the mycorrhizal inoculation is achieved. In addition, higher values are achieved in these indicators compared with the results reached with each one separately.

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