NODULATION SUCCESS AND PERSISTENCE OF RECOMMENDED INOCULUM STRAINS FOR SUBTROPICAL AND TROPICAL FORAGE LEGUMES IN NORTHERN AUSTRALIA

The need to inoculate tropical and subtropical forage legumes in northern Australia was assessed by comparing inoculated with uninoculated and plus nitrogen treatments in several important pasture improvement regions. No growth responses were observed with Siratro (Macroptilium atropurpureum), Townsville Stylo (Stylosanthes humilis), Clarence glycine (Neonotonia wightii) and some genotypes of S. guianensis. The proportion of nodules formed by the inoculum strain was < 10%. Growth responses were obtained, however, with Greenleaf desmodium (Desmodium intortum), Belalto centro (Centrosema pubescens) and some lines of S. guianensis but were variable between sites. Where a response was observed, the proportion of nodules formed by the inoculum strains in the establishment year varied between 30 and 90%, and declined to < 10% within 2-5 yr but without corresponding loss of yield. These results define legume and region combinations for which it is important to inoculate seed to ensure early nodulation and good first year growth.