STUDY ON SULPHUR CRITICAL AND MOST EFFICIENT PERIODS OF CANOLA-DOUBLE LOW OILSEED RAPE (BRASSICA NAPUS CV. OSCAR)

Studies on effect of sulphur(S) supply on growth and development of canola - double low oilseed rape were carried out by using sand culture and adjusting S levels to adequate (H, 0. 75mmol/L) or deficient (L, 0. 075mmol/L) according to five growth stages in glasshouse. The results indicated that the symptoms of S deficiency appeared more quickly with low S supply during earlier stages rather than middle or late ones. The symptoms appeared and disappeared on new tissue first when provided deficient or sufficient S supply. The seed yield and oil content were affected more heavily when supplied low S during middle or late stages than that during early ones. The optimum yield was obtained by at most one low S period during any one of the 5 stages except during rosette or flowering. No or nearly no economic yield was obtained while supplied low S throughout, neither one nor two periods before stem elongation. Meanwhile. oil.glucosinolate and S concentrations were increased by adequate S supply during late stages. Compared seed yield with low S supply at each period, the critical peroid of S nutrition was during rosette while the most efficient period was during flowering. The vegetative growth was improved by early period of adequate S supply. and the reproductive growth, such as pod numbers. seeds weight, etc. was increased significantly by increasing S during middle or late period. In addition. early low S supply delayed flowering, and the maturity was delayed when S level was increased during the middle or late stage because of the plant growing flowering and fruiting again. Pods were distributed discontinuously on the fruiting branches with low S supply during flowering only. There were two peaks of S uptake during whole growth period of ollseed rape. One was from flowering to pod filling, the other was from rosette to stem elongation.However, these two peaks were just well related to S most efficient and critical periods,in which enough attention should be paid in S management of the crop.