Resumen
Around 78% of the air is composed by nitrogen and this element is the third most important to the maintenance of life on the planet, after the carbon (C) and oxygen (O). The greatparadox is life in earth it that this gas (N2) is inert and can only be reduced to a form assimilated by plants by different genus of bacteria called diazotrophs. These bacteria interact with other organisms including agricultural crops as the most famous one, the rhizobia of soybean. Another example recently incorporated to the cereal production routine is the application of another bacterium called Azospirillum brasilense described by the research group of Johanna Döberenier in the 80?s. The association of diazotrophs and grasses has been studied for about 60 years and revealed that in addition to providing nitrogen to the crops (contributing with up to 58% of its necessity), can also produce phyto-hormones, act as a biocontrol agents, solubilize phosphates and some other features; helping plants in the response of environmental stresses and refl ecting in crop productivity using reduced doses of N-fertilizer. With the objective of develop a cropmanagement based on biological nitrogen fi xation and a recommendation of inoculant application in order to improve the utilization of N-fertilizers, also preconized by the green revolution, made this research recognized worldwide for its innovation that advocates the use of a conservative practice, keeping the man in the fi eld, producing more without harming the environment.