Performance of temperate and subtropical forage legumes when over-seeding native pastures in the basaltic region of Uruguay

In 1997, an integrated plant breeding program was initiated at the National Agricultural Research Institute (INIA) Uruguay, to develop forage legumes and root nodule bacteria which were able to be productive in co-existence with the native (grass-dominant) vegetation when grazed by cattle and sheep. The program was conducted in parallel with rhizobial strain selection by the Rhizobium–Biological Nitrogen Fixation Unit of the Soil Microbiology Department of the Ministry of Livestock, Agriculture and Fisheries of Uruguay and the Centre for Rhizobium Studies (CRS), Murdoch University, Western Australia. Between 1998 and 2000, 326 temperate and subtropical forage legume species originating from 38 ex-situ seed collections were evaluated in 3 plantings on: red lithosol, black lithosol and vertisol soils at Glencoe Research Station in Uruguay. Row–column field designs were used. Forage production at the end of the second year of evaluation was used as the key selection parameter for the introduced legumes because their success required persistence in the pasture either vegetatively or by natural reseeding. This study identified a set of promising legumes and strains of Rhizobium that are now available for further study and breeding in Uruguay as well as other countries with a similar climate. The methodology developed in this study may be applicable to forage selection programs in which competition between annual and perennial species is expected to influence outcomes