Mechanization is used in the harvesting of legumes. - - Biological Nitrogen Fixation. The following Brazilian Government agencies, The Centre for Nuclear Energy in Agriculture, The Institute for Agronomic Research, the Ministry of Agriculture and the Soils Department of the University of Rio Grande do Sul, collaborated with FAO in the production of a filmstrip on the symbiosis between legumes and rhizobium bacteria. These photographs, from the filmstrip, illustrate the results of experiments in the selection of the most efficient rhizobium strains.