engleski

Nutritional quality of broccoli cultivars as affected by nitrogen fertilization

Variable content of bioactive compounds and minerals are the main problem in the production of vegetables as functional food, due to genetic, abiotic and agronomic factors (especially fertilization) which may affect the nutritional and medicinal value of vegetables. In order to achieve the higher yield, producers often apply large amounts of nitrogen fertilizer, which can result in accumulation of nitrate and reducing the quality of broccoli. There are no results about the content of bioactive compounds and minerals in broccoli inflorescence grown on the principles of good agricultural practices in Croatia. The research was set up to determine the effect of nitrogen fertilization on the content of glucosinolates, some minerals (potassium, calcium and nitrogen) and nitrate levels in the broccoli top inflorescence during different growing periods (GP). The field trials were conducted in spring-summer and summer-autumn GP in 2009 according to four-replication randomized complete block design. Two broccoli cultivars ('Marathon', 'Parthenon') and four levels of nitrogen fertilization (0, 60, 120, 240 kg N/ha) were tested. There was a significant effect of cultivar and rate of nitrogen fertilizer on the nutritional quality of broccoli top inflorescence in each GP. The average values of total glucosinolates (12.82 μmol/g dw) and calcium (78 mg Ca/100 g fw) in broccoli top inflorescence were significantly higher during spring-summer GP as a result of less favorable abiotic factors and transpiration intensity. The prevailing glucosinolates in that GP were glucobrassicin and neo-glucobrassicin. In the summer-autumn GP higher amounts of potassium, nitrogen and nitrate (437 mg K/100 g fw, 531 mg N/100 g fw and 553 mg NO3/kg fw) were achieved, while the dominant individual glucosinolates were glucoraphanin and glucobrassicin. Combination of 'Marathon' and fertilization with 240 kg N/ha resulted with high values of total glucosinolates and some minerals with nitrate content in the allowed range (FAO).

Brassica oleracea L. var. italica; glucosinolates; minerals; nitrates

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