PHOSPHATE FERTILIZATION CAN INCREASE YIELD OF PRODUCTIVE GRASS PEA (Lathyrus sativus L.) CROPS IN P-RETENTIVE SOILS

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.