Process for the biofertilization of a culture using an inoculum Azotobacteraceae applied to foliage of a preceding culture, characterized in that the inoculum is applied in the phenological gap between the histological maturity stage of the vegetative parts and the stage of physiological maturity of the reproductive parts of this previous culture still "on feet" and eventually producing a quantity of straw residues that can be incorporated into the surface of arable soils. The crop is a large non-Fabaceae winter crop included in a group consisting of cereal straw crops, rapeseed, flax or even an intermediate culture nitrate trap (Cipan). The stage of histological maturity of the vegetative parts of the previous culture is in accordance with the phenological stages between indices 55 and 59 of the so-called Zadok and / or BBCH scales, whereas the stage of physiological maturity of the reproductive parts of the previous culture is in accordance with phenological stages between the indices 73 and 75 of the so-called Zadok and / or BBCH scales. The amount of mulch residues that can be incorporated in arable soil surfaces is of the order of at least 5 to 8 tonnes per hectare and is not harvested but left on the soil for incorporation. In addition, the Azotobacteraceae inoculum advantageously contains bacterial cells producing auxins mainly via the metabolic intermediate which is AMI (indole-3-acetamide)； it advantageously comprises between 1 and 10 × 10 4 Azotobacteraceae cells and between 10 and 20 g of tryptophan per dose-hectare.Procédé de biofertilisation d'une culture à l'aide d'un inoculum Azotobacteraceae appliqué aux feuillages d'une précédente culture caractérisé en ce que l'inoculum est appliqué dans l'interstice phénologique compris entre le stade de maturité histologique des parties végétatives et le stade de maturité physiologique des parties reproductives de cette précédente culture toujours « sur pieds » et produisant à terme une quantité de résidus paille
