Arbuscular mycorrhizal inoculation and phosphorus levels in the production of andropogon-grass, in non sterile substratum

Abstract

The objective of this work was to evaluate the influence of arbuscular mycorrhizal fungi and phosphorus fertilization in the production and quality of the forage of the grass Andropogon gayanus cv. planaltina, in soil of low natural fertility. The experiment was carried out in greenhouse conditions and the experimental design was set up in randomized blocks, with a 4x3 factorial scheme, involving four levels of P (0, 60, 120, and 240 mg P dm^-3 of soil), three microbiology treatments (soil without inoculation; soil inoculated with FMA-Glomus clarum, and soil inoculated with FMA - native), and three replications. The evaluated variables were the productions of shoot (DMS) and root (DMR) dry matter; the accumulated amounts of PB, P, K, Ca, Mg, S; the percentage of mycorrhizal colonization and the density of spores in the soil. The results demonstrated that the increase in the levels of P promoted significant increments in the production of DMS and DMR, and accumulation of the mentioned nutrients. These results were maximized by the presence of the mycorrhizal inoculation, with prominence for the species Glomus clarum to variables DMS, P, K, Ca e Mg. The percentage of mycorrhizal colonization and density of spores in the soil decreased with the increase in the P levels, and were not influenced by the microbiological treatments.