Trends in rhizobial inoculant production and use

Rhizobia inoculants have contributed to increase N-2 fixation and yield in legumes crops. However, most of the inoculants produced world-wide are of p oor or suboptimal quality. We discuss here why some of them are poor produc ts and how to improve their quality and efficacy. Reported data on the inoc ulation rate effect can be used to design good inoculants. Technologies are now available to produce inoculants with a shelf-life of more than 1 year. Available quality control methods can help to improve the quality of inocu lants although they do not take into account the physiological satus of the rhizobia. Unfortunately quality control is not commonly used except in maj or inoculant companies and the quality of inoculants sold on the market is low. The need for an increase in quality standards is discussed especially for the number of rhizobia delivered per seed and for the presence of conta minants. Some new technologies which able to increase efficacy and reliabil ity of inoculation are discussed.