Lentil production in southern Chile is subject to significant seasonal fluctuations in solar radiation received during the reproductive stage, with an average variation ranging from 300 to 650 g cal cm2 day-1. To quantify the effect of reducing incident Iight on crop performance, artificial shading experiments were conducted with 80% Iight reduction during different periods spanning the reproductive stage, as well as various degrees of shading (0, 20, 35, 50 and 80%) throughout. Shading was achieved by using a black polypropylene net placed at 0.8 m above soil surface. The experiments were carried out during the 1991/92, 1992/93 and 1993/94 cropping seasons at the Centro Regional de Investigación Carillanca, INIA (38°41' S, 72°25' W). The effect of 80% shading on seed yield was dependent upon the period at which the treatment was imposed. Seed yield reduction was higher when shading occurred during the growth stages R3-R5, accounting for 35, 48 and 59% yield losses for the 1991/92, 1992/93 and 1993/94 seasons, respectively. No significant differences were detected between R1-R3 and R5-R8 periods, with seed yield losses averaging 39 (1991/92), 10 (1992/93) and 25% (1993/94). Variations in seed yield due to shading were explained mainly by a reduction of total pods m-2 (R1-R3), a reduction of total pods m-2 and an increase in empty (flat) pods (R3-R5), and a reduction on the average seed weight (R5-R8). As expected, the higher losses occurred on treatments exposed to two (R1-R5, R3-R8) or three (R1-R8) periods of shading. Grain yield under different degrees of shading was significantly reduced, with responses fitted to the functions Y = 2.020-32.5s+0.18s2 (1992/93) and Y = 2.172-25.6s-0.04s2 (1993/94). Reduction on seed yield was associated to a decrease in total pods m-2 and average seed weight, whereas empty pods increased significantly only at near 80% shading. These res |
ChileanJAR
