GROWTH AND YIELD OF WHITE LUPIN (LUPINUS-ALBUS) UNDER MEDITERRANEAN CONDITIONS - EFFECT OF SOWING DATE

The sowing date, which depends on climate and on genetic characteristics of the species and cultivars, has a marked influence on crop growth and yield. A 5-year study of white lupin (L. albus) was conducted under the Mediterranean conditions of southern Spain in order to determine the influence of autumn (October/November) and winter (December/January) sowing dates on growth and grain yield. The duration of the different growth stages and thermal time (base 4-degrees-C) were estimated for: emergence (V0), initiation of flowering (R1), end of flowering and beginning of pod filling (R4), and harvest maturity (R8). The accumulation of dry matter, leaf area index (LAI), leaf area duration (LAD), pod setting %, grain yield, yield % of the main stem and yield components (plants m-2, pods plant-1, seeds pod-1, and mean seed mass) were also measured. A randomized block with four replications was used and an analysis of linear correlation between the parameters measured and path coefficients analysis between grain yield and its components was estimated. The complete growth period had an average duration of 222 days (2417 thermal units) in the case of the autumn-sown crop and 173 days (2096 thermal units) with winter sowing. The periods V0-R1 and R1-R4 were shorter in the case of winter sowing, due to the influence of vernalization, photoperiod and water shortage in spring. The accumulation of dry matter and grain yield was greater for autumn sowing (6110 kg ha-1 and 1868 kg ha-1) than for winter sowing (3810 kg ha-1 and 1178 kg ha-1), as were maximum LAI and LAD (2.2 and 171 days and 1.6 and 83 days, respectively). The number of pods plant-1, mean seed mass and pods m-2 were the components most influenced by sowing date, showing significantly higher values in autumn. There was a positive correlation between yield and the number of pods m-2 and mean seed mass. Path coefficients analysis showed a marked direct effect of mean seed mass on the yield; indirect effects were negligible, with the exception of mean seed mass.