The Effect of Differentiated Nutrition on the Content of Antioxidants in Broccoli

The aim of this work is to determine the impact of differentiated nutrition, using different rates of nitrogen and sulphur, on the level of antioxidants, particularly vitamin E1 (α-tocopherol), vitamin C and β-carotene in the broccoli rosette. The experimental broccoli variety was Tiburon F1. It is a strong medium-late variety with a vegetation period of 82 days. In the 3-year field trial we observed the effects of different rates of nitrogen and sulphur on the amount of antioxidant compounds in broccoli. The experiment consisted of four fertilisation treatments: 1) unfertilised control, 2) fertilised with 200 kg N.ha−1, 3) also fertilized with 200 kg N.ha−1 and supplemented with 50 kg S.ha−1, 4) 200 kg.ha−1 and 60 kg S.ha−1 was applied. To determine the amount of β-carotene and vitamin E1, the slightly modified method of Olives Barb et al. (2006) was used. The vitamin C content was determined by titration. Nitrogen nutrition has a significant impact not only on the amount of harvested broccoli, but also on the content of β-carotene, vitamin C and vitamin E1. The average content of β-carotene for the entire experimental period ranged from 24.84 mg.kg−1 to 30.13 mg.kg−1 of fresh mass. The content of β-carotene in broccoli rosettes increased as per the following order of treatments: control > N:S (200:50 kg.ha−1) > N:S (200:60 kg.ha−1) > N (kg.ha−1). The β-carotene content increased significantly only in treatment 2 (30.13 mg.kg−1) as compared to all the other treatments. The level of vitamin C revealed the significant effect of fertilisation in all the treatments (567.9–614.2 mg.kg−1) in contrast to the control variant (528.4 mg.kg−1). What is more, in treatment 4 the content of vitamin C increased significantly in contrast to fertilised treatments 2 and 3. The average content of vitamin E1 ranged from 4.33 mg.kg−1 to 4.88 mg.kg−1 of fresh mass. There were no significant differences among the untreated control and fertilised treatments 2 and 3. The only significant decrease in the content of vitamin E1 was detected in treatment 4 as against the unfertilised treatment 1.