Two field experiments were conducted in order to evaluate the effect of N, P, K fertilization, with and without liming, on the total green matter and seed production of sunn hemp (Crotalaria juncea L.). The experiments were done in the experimental stations of the Instituto Agronômico of State of São Paulo, Brazil, located in Campinas and Tatuí, during the years of 1969/1970, in soils of the group Latosol <<Roxo>>. The results obtained indicated a positive effect of P fertilization on the sunn hemp yield, in the soils that presented less soil P content. Significant increases in yield were obtained with the application of dolomitic lime, specially in the experimental station of Tatuí.