1. Andrews M, Lea PJ (2013) Our nitrogen ‘footprint’: the need for increased crop nitrogen use efficiency. Ann Appl Biol 163(2):165–169
2. Araujo ASF, Lopes ÂCA, Gomes RLF, Beserra Junior JEA, Antunes JEL, Lyra MCCP, Figueiredo MDVB (2015) Diversity of native rhizobia-nodulating Phaseolus lunatus in Brazil. Legume Res 38(5):653–657
3. Bremner JM (1965) Organic forms of nitrogen. In: Black CA (ed) Methods of soil analysis, 1rd edn. American Society of Agronomy, Madison, pp 1238–1255
4. Costa EM, Ribeiro PRA, Lima W, Farias TP, Moreira FMS (2017) Lima bean nodulates efficiently with Bradyrhizobium strains isolated from diverse legume species. Symbiosis, accepted for publication
5. Döbereiner J (1966) Evaluation of nitrogen fixation in legumes by the regression of total plant nitrogen with nodule weight. Nature 210:850–852