Late Senescence Oil Losses in Soybeans 1

The objectives of this study were to determine 1. whether oil was lost during late senescence from the whole of the seed fraction of the soybean cultivars ‘Lee’ and ‘Bragg’ and 2. whether late senescence oil losses occurred in six commercial cultivars at different sites spanning almost 5° of latitude. In the first year, plants of Lee were grown in pots beneath a rainshelter at Camden, New South Wales. Significant reductions (p < 0.05) in oil percentage, oil content per seed (averaged over the whole seed fracton) and oil yield per plant occurred during the final stages of podfilling (50 to 60 days after flowering). In the following year, the average oil content of Bragg seed, grown in the field at Camden, was measured regularly during crop senescence. Oil content per seed declined significantly (p < 0.05) as the majority of the pods changed color from yellow to brown, which corresponded to a fruit maturity index change from 4 to 5. In another experiment, where pods were removed at mid senescence (R7) and at plant maturity (R8) from a range of cultivars (Maturity Groups V to VII) grown at five sites in NSW. Oil losses occurred at four of the five sites in New South Wales and in all cultivars except the partially indeterminate, earliest maturing Ruse. Oil losses were not correlated with late senescence increases in seed protein content from different cultivars. The economic consequences of these late senescence oil losses can be quite significant. The cv. Forrest lost more than one‐eighth of the total oil produced by the crop, without any concomitant increase in protein or seed yield.