DRY-MATTER AND NITROGEN ACCUMULATION AND SEED YIELD IN DETERMINATE AUTUMN-SOWN WHITE LUPINS (LUPINUS-ALBUS L)

Determinate autumn-sown white lupins (Lupinus albus L) are new types which are potentially interesting for the improvement of yield stability and for cultivation of lupins in northern Europe. Two determinate genotypes were studied in 1990/1991 and 1991/1992 at Lusignan, France, under 17 combinations of sowing date, density and irrigation. Dry matter production was 1 061 g/m2 on average and the duration of the growing cycle was 2 284-degrees-C.d (degree.day) from sowing (base 3-degrees-C). Late sowing date and low density induced a reduction of total biomass at maturity. The leaf area index (LAI) was 2.6 on average at its maximum and the mainstem was the level with the highest LAI, followed by the first-order branches and the second-order branches. Mean seed yield was 3.65 t/ha, and was rather stable over the agronomic conditions. Yield was correlated with total above-ground matter, but was independent of harvest index. Yield was also correlated with number of seeds per M2 but was independent of mean seed weight. Yield on the mainstem was, statistically, totally explained by the number of mainstem leaves per M2. Relationships between the yields of the different pod orders were detected. Nitrogen accumulation followed dry matter accumulation, and the mean nitrogen harvest index was 0.82. All the results were compared with those obtained on the indeterminate, autumn-sown cultivar Lunoble.