Chilean lentil (Lens culinaris Medik.) shows a large variation in seed size within a same cultivar due to both the grading procedures as well as the dilferent environments where it grows. To evaluate the elfect of seed size on crop performance, seeds of cv. Araucana-INIA from two origins, averaging 6.8 and 8.2 9 100-seed weight, were graded into three sizes according to seed diameter (5, 6 and 7 mm) and sown at constant density (92 seeds/m2). The study was conducted in two environments of contrasting productivity in the IX Region, Chile. The elfect of seed origin was not significant in any evaluated parameter. Seed grading did not alfect germination but field emergence was significantly reducad in both environments with reducing seed size. Seed yield was not alfected by seed grading in the more productive environment (average 2,283 kg/ha) whereas it was reduced from 1,422 (7 mm) to 1,183 (5 mm) kg/ha in the less productive one. Averaged across environments, the harvested fractions were 8.9, 5.3 and 4.9% (5 mm) and 22.2, 26.7 and 28.2% (7 mm), for 5, 6 and 7 mm seeds, respectively, with the 6 mm not being alfected by grading. According to the results, seed size would be 01 lillle value under productive environments whereas it may haya agronomic importance under an environrnent that restrict growth. |