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Content of Broccoli Macroelements and Glucosinolates as Affected by Sulphur Fertilization

Variable content of glucosinolates and minerals is the main problem in the production of vegetables as a functional food, due to genetic, environmental factors and cultural practices (especially fertilization). The research has been set up to determine the effect of sulphur fertilization on the content of some macroelements (potassium, phosphorus and calcium), nitrates and glucosinolates in the broccoli top inflorescence. The two- factorial field trial was conducted during the spring/summer growing season in 2011. Treatments were arranged according to the randomized complete block scheme with four replications. Two broccoli cultivars (‘Marathon’, ‘Parthenon’) and four levels of sulphur fertilization (0, 25, 50 and 90 kg ha-1 S) were tested. The obtained results indicate a significant effect of cultivar and sulphur fertilization on the broccoli top inflorescence nitrate level and content of macroelements and glucosinolates. ‘Parthenon’ achieved higher values of nitrates [508 mg kg-1 NO3 of fresh weight (fw)], dry matter (12.73 %), potassium, calcium and phosphorus (455 mg K, 46 mg Ca and 22 mg P 100 g-1 fw). Regarding the sulphur fertilization, the highest values of potassium, phosphorus, glucoraphanin and total glucosinolates were obtained with fertilization of 25 kg ha-1 S. The total glucosinolates content varied from 5.67 to 16.37 µmol g-1 of dry weight (dw) and prevailing individual glucosinolate was glucoraphanin. Combination of ‘Parthenon’×25 kg ha-1 S resulted with the highest values of dry matter, glucoraphanin, potassium and phosphorus of broccoli top inflorescence, also with nitrate content below 450 mg kg-1 NO3.

Brassica oleracea var. italica; potassium; calcium; nitrate; glucoraphanin

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