The following research assessed the effect of the biostimulant isabion and zinc on the productivity and quality parameters of two cabbage (Brassica oleracea L.) hybrids. The experiment, carried out in the autumn of 2023–2024, transpired at the University of Kerbala, District Al-Husseiniyah, Kerbala Governorate, Iraq. The experiment, laid out in a randomized complete block design, had a split-plot arrangement with three replications. The main plots comprised two cabbage hybrids: Zeina F1 (red cabbage) and Wight Moon (green cabbage). Meanwhile, the subplots included eight fertilizer combinations with different ratios. Results showed hybrid green cabbage was superior in head weight, marketable yield, total yield, and protein percentage in leaves, with average values of 1,087.34 g head^-1, 31.32 t ha^-1, 38.72 t ha^-1, and 12.44%, respectively. As for fertilizer treatments, evidently, the fertilizer combination Isabion (9 L ha^-1) + zinc (1 g L^-1) excelled in head weight, marketable yield, total yield, total dissolved solids, ascorbic acid, and protein content in leaves. Their average values are 1,252.43 g head^-1, 36.07 t ha^-1, 42.93 t ha^-1, 4.48%, 69.04 mg 100 mg^-1, and 17.26%, respectively. The interaction between both factors was also significant for all the cabbage traits under study.

Keywords: Cabbage (B. oleracea L.), biostimulant Isabion, zinc, growth and yield traits, ascorbic acid, protein content

Key findings: Results revealed hybrid green cabbage (B. oleracea L.) was leading in head weight, marketable yield, total yield, protein content, and ascorbic acid in the leaves. As for fertilizer treatments, the fertilizer combination of Isabion (9 L ha^-1) + zinc (1 g L^-1) also excelled in all the cabbage traits.