Contribution of arbuscular mycorrhizal inoculation to the reduction of phosphorus fertilization in Brachiaria decumbens

Abstract

An experiment was conducted on a Red Ferralitic Lixiviated soil in order to assess the contribution of arbuscular mycorrhizal inoculation to reduce phosphorus fertilization in Brachiaria decumbens cv. Basilisk. Doses of 0, 30, 60 and 90 kg P2O5 ha-1 year-1, alone and combined with the inoculation of arbuscular mycorrhizal fungal strain Glomus cubense, previously selected for its high efficiency, were distributed in a randomized block design with 4x2 factorial arrangement and four replications. The experiment was conducted under irrigated conditions and lasted two years. G. cubense significantly increased mycorrhizal colonization percentages, visual density and spore number in the rhizosphere, although the values of those variables decreased with the highest doses of P2O5. In non inoculated treatments, the highest yields and P extractions in the aerial biomass were obtained with doses of 30-90 kg of P2O5 ha-1, with no significant differences between them, but only with the inoculation of G. cubense, during the first year of the establishment of grass both indicators reached values similar to those obtained with phosphoric fertilizer applications without inoculation. The influence of G. cubense was observed until the rainy season of the second year, although fungal variable values, yields and P exports with the aerial biomass indicated a decrease in the effectiveness of inoculation, in relation to the first year.