Above- and below-ground responses of Eragrostis and Bouteloua grass seedlings to the plant-growth-promoting bacterium Azospirillium brasilense

Two experiments were performed to determine the effects of inoculation with N2 fixing bacterium Azospirillum brasilense on forage production and root growth in seedlings of Wilman lovegrass, weeping lovegrass, and sideoats grama. Two sources of inorganic nitrogen (N) were tested: Urea, CO(NH2)2 (45%) and ammonium nitrate NH4NO3 (33.3%). Crude protein (CP), calcium (Ca) and phosphorous (P) concentrations were determined. In both experiments top dry matter (DM) production was significantly affected for grasses and inoculation but no differences were found for inorganic nitrogen applications. Maximum amount of top DM was obtained with the Wilman lovegrass with 5.70 g, weeping lovegrass reached 2.70 g, and sideoats grama only reached 1.58 g. Inoculated treatments reached 3.37 g while the no-inoculated treatments obtained 2.74 g. A similar trend was also noted for root phytomass. CP, Ca and P concentrations for the first experiment did not show any trend; therefore, they were not determined for the second experiment. Inoculation of grasses with A. brasilense may be a feasible practice for seeding some rangeland where N deficiency is a problem.