Yield, physicochemical and compositional traits of ‘off-season’ carrot as affected by nitrogen fertilization and harvest time

Nitrogen (N) fertilization is essential for adequate earliness, crop productivity and commercial attractiveness of early carrot. Nonetheless, with a view to ensuring a high-quality and sustainable product, today it is imperative to reduce the N fertilization rates usually adopted in its cultivation areas of southern Italy. On the other hand, other factors such as different harvest times, which are used to modulate the product’s presence on the market, contribute to modifying carrot quality, but the combined effects of reduced N fertilization rates and different harvest times on carrot yield and quality has not been investigated. A field experiment was conducted in Sicily, Italy, to investigate the effects of three nitrogen (N) fertilization rates (N60, N120, and N240, corresponding to 60, 120, and 240 kg ha-1, respectively) and two harvest times (T1 and T2, at 186 and 200 days after sowing) on yield, physicochemical, and compositional traits of ‘Dordogne’ carrot. Compared to N60, N120 significantly increased marketable root yield by 42 and 49% at T1 and T2, respectively, while the effect of N240 was only significant at T2, with a 25% increase compared to N120. N120 and T2 reduced unmarketable root yield. Physicochemical and compositional traits were similar between N60 and N120, but N240 negatively affected nitrate content, total phenolics, and antioxidant activity. These results demonstrate the potential, particularly for early harvests, to reduce the N supplies commonly used in the region (240 kg ha-1) without compromising marketable carrot yield, while enhancing important functional and quality traits.