ACCUMULATION, DISTRIBUTION AND REDISTRIBUTION OF DRY-MATTER AND MINERAL NUTRIENTS IN FRUITS OF CANOLA (OILSEED RAPE), AND THE EFFECTS OF NITROGEN-FERTILIZER AND WINDROWING

Field studies were made at Ariah Park and Cowra to investigate the acc umulation distribution of dry matter and 12 mineral nutrients in fruit s (pods) of canola (oilseed rape and to assess the significance of red istribution of nutrients from the pod walls to the seeds. Flowers 4-6 from the base of the primary inflorescence were tagged at anthesis, an d pods which developed from these were harvested at weekly intervals u ntil maturity. Pods reached maturity 82 days after anthesis of the par ent flowers. N fertilizer increased seed yields at both sites, but had negligible effects on the dry matter per pod, pod length, 1000 seed w t, seed number per pod, seed oil concentration, and concentrations of mineral nutrients in the pod walls and seeds. Similarly, there were no differences in these parameters due to locality, with the exceptions that seed oil per cent and concentrations of S and Mn in the pod walls and Mn in seeds were higher at Cowra than at Ariah Park. Pods had att ained their maximum length and fresh and dry weights by the end of the first half of their development, but seeds had accumulated only 35% o f their mature dry weight at this stage. Seeds gained dry matter after dehydration of the fruit began, but the pod walls did not. Seeds had 61% of the pod's dry matter, >70% of its P, N, Zn, Fe and Mg, 30-55% o f its K, S, Mn, Cu and Ca, but <20% of its Na and Cl. Dry matter was r edistributed from the pod walls with 20% efficiency, and nutrients wit h from 17% (Cu) to 88% (P) efficiency; however, there was negligible r edistribution of K, S, Ca, Na, Cl, Fe and Mn from the pod walls. Redis tributed dry matter and nutrients from the pod walls could have provid ed from 11% (dry matter) to 25% (N) of the amount in mature seeds. Con centrations of N, P, Mg, Mn, Zn and Cu in the pod walls declined as th ey developed, whereas those of Ca and Cl increased. Concentrations of nutrients in developing seeds remained fairly static. Windrowing plant s when 40% of the seeds had changed to their mature colour did not aff ect seed oil per cent or concentrations of nutrients, but reduced seed size and seed yields by 10%. Data from the pod study also support the current recommendation to windrow when 40-60% of seeds reach their ma ture colour.