Growth and yield of white lupin under Mediterranean conditions: Effect of plant density

Abstract

In a species with a well-defined growth pattern such as lupin, changes in plant density alter the structure and size of the canopy and affect grain yield components. A 4-yr study of autumn-sown white lupin (Lupinus albus L.) was conducted under rainfed Mediterranean conditions in southern Spain to determine the influence of plant density on biomass and grain yield. Three plant densities (20, 40, and 60 plants m-2) were tested in a randomized complete block design with four replications. Between-year variation in rainfall during the growing season had more marked effects on growth indices than on grain yield. Dry matter accumulation, leaf area index, and leaf area duration were directly related to plant density; however, leaf senescence was higher with increased density. While grain yield exhibited no significant differences among the densities studied, the harvest index decreased with increasing plant density. With increasing plant density, the number of pods per plant decreased, whereas number of seeds per pod and mean seed mass remained unaltered. Path coefficient analysis showed that pods per plant and per unit area had most important direct and indirect effects on grain yield. The high plasticity of the canopy structure offset changes in grain yield components of lupin which resulted from differences in plant density and led to a constant grain yield. This feature can be turned to advantage under the extremely variable conditions of the Mediterranean climate.