Influence of nitrogen treatments on some nutrient concentration and bioactive compounds of broccoli.

Background: Nitrogen fertilization in broccoli is very important for plant growth and productivity. However, it is known that the nitrogen source of the nitrogen fertilizer is also effective on quality parameters. In this study we investigated the effects of different nitrogen sources (ammonium sulphate and calcium nitrate) on bioactive compounds and leaf nutrients of broccoli cultivars (Monet, Italian and Karadede).

Results: The highest total phenolic content was 0.24 mg g^- 1 fw in cultivar Monet. Nitrate-based fertilizer treatments provided higher total phenolic (0.28 mg g^- 1 fw) and flavonoid (0.56 mg g¹ fw) contents and FRAP (0.24 mmol g^- 1 fw) values compared to ammonium-based fertilizer treatments. On the other hand, DPPH (0.77 mmol g^- 1 fw) values were higher in the ammonium nitrogen treatments. Among the cultivars, Monet had the highest total phenolics, flavonoids and FRAP values. When leaf nutrient concentrations were analyzed, ammonium sulfate application resulted in higher sulfur (0.86%), zinc (20.72 mg kg^- 1) and manganese (28.80 mg kg^- 1) concentrations compared to calcium nitrate. Calcium nitrate treatment provided the highest calcium (2.09%) and iron (37.50 mg kg^- 1) concentration in Monet cultivar. Phosphorus (0.31-0.35%) and magnesium (0.073-0.084%) concentrations differed among cultivars.

Conclusions: In conclusion, the choice of nitrogen source and cultivar in broccoli cultivation plays an important role in the bioactive compound profile and nutrient composition of the broccoli crop. The results provide useful information for the improvement of broccoli quality.