The effect of P fertilization on grass pea (Lathyrus sativus L.) yield and yield components was evaluated on soils with low P availability and high P retention capacity in small-scale farms of the Araucanía Region in southern Chile. Trials were conducted during 2000-2001, 2001-2002, and 2002-2003, in six sites; three sites in Lumaco and three in the Selva Oscura area. Six rates of P (0, 21.8, 43.6, 65.4, 87.2, and 109.0 kg ha-1) were evaluated in a randomized complete block design with four replicates. Grass pea cv. Luanco-INIA was sown at 47 seeds m-2. Mean grain yield for all trials was 2456 kg ha-1. Phosphate fertilization increased grass pea grain yield in both areas during 2000 and 2001. There was no significant effect in 2002. The 2002 cropping season had an unusually high spring-summer rainfall, which may have enhanced the P mineralization rate from organic soil fraction, and thus P availability. According to this study, grass pea crops in soils with < 10 mg kg-1 of available P-Olsen should respond to P fertilization.