The present invention concerns a method for increasing the biostimulation efficacy of a live bacterial strain or a composition containing same, characterised in that the method comprises a step of inactivating the live bacterial strain, the inactivated bacterial strain obtained in this way having a higher biostimulation efficacy on the development of plants than that obtained with the same bacterial strain when live or with a composition containing same. The present invention also concerns an inactivated bacterial strain and a composition comprising same, for improving the development of a plant.
