AGRONOMIC APPLICATIONS OF AZOSPIRILLUM - AN EVALUATION OF 20 YEARS WORLDWIDE FIELD INOCULATION

By evaluating worldwide data accumulated over the past 20 years on fie ld inoculation experiments with Azospirillum, it can be concluded that these bacteria are capable of promoting the yield of agriculturally-i mportant crops in different soils and climatic regions. Various strain s of A. brasilense and A, lipoferum have been used to inoculate cultiv ars of different species of plants. It is however difficult to accurat ely estimate the percentage of success due to Azospirillum inoculation . The data indicates 60-70% occurrence of success with statistically s ignificant increases in yield of the order of 5-30%. Successful inocul ation experiments appear to be those in which the researchers have pai d special attention to the optimal number of cells of Azospirillum in the inoculant, using inoculation methods where the optimal number of c ells remained viable and available to colonize the roots. Furthermore, experiments taking into consideration the potentialities and limitati ons of this technology have been better able to explain successes and failures. The different formulations (analogous to those of rhizobia) of the genus Arospirillum, irrespective of their form of application a nd their mode of action on the plant, are indeed inoculants. The term biofertilizer is not appropriate as it does not replace fertilizer but improves their utilization. We very strongly suggest the implementati on by regulatory authorities of quality control on commercial Arospiri llum inoculants.