DEVELOPMENT AND GROWTH OF WHITE LUPIN - IMPLICATIONS FOR CROP MANAGEMENT

Grain yield of spring white lupin (Lupinus albus L.) varies greatly wi th sowing date and density; These effects seem to be related to variab ility of the canopy architecture. To explain and predict such effects, plant growth and development were characterized at different sowing d ates and densities and were related to the distribution of seed number between the main stem and branches. 'Lublanc' white lupin was sown in field environments for 9 Jr, in the greenhouse for 2 yr, and in a gro wth cabinet for 1 yr at different densities and at different dates wit hin seasons. Current management techniques were applied. Measurements included successive numbers of main-stem leaf primordia, successive nu mbers of main-stem leaves, date of flower initiation on the main stem, date of flowering on the main stem (SF), absorbed photosynthetically active radiation (PAR) by linear sensors (1 gr) or by leaf area index measurement (2 yr), and weekly accumulated drg matter (DM). Flowering date varied between 366 and 621 degree-days (base 3 degrees C) from em ergence and was closely related to the final number of main-stem leave s. Leaf number was linked to cumulative vernalizing degree-days receiv ed by the apex. Thus, SF was dependent on temperatures during early gr owth. Absorption efficiency of PAR (epsilon(a)) varied with plant dens ity, but at high plant densities, regardless of the year, a single cur ve represented epsilon(a) change over time. This limit curve gives the maximum possible epsilon(a), at a given date. Until seed filling bega n, the coefficient of absorbed PAR conversion was 1.90 g DM MJ(-1). Ou r results contribute to improved management of lupin crops by suggesti ng cultural practices to minimize climatic hazards from drought and hi gh temperatures.