The presented maize experiment commenced in autumn 2022 at the Al-Hussainiya, Kerbala, Iraq. The experiment comprised two factors: the first included nitrogen (0, 150, and 300 kg N ha^-1) and phosphorus (0, 50, and 100 kg P ha^-1), and the second was the seaweed extract (2 and 4 ml L^-1) used as a foliar application. The seaweed extracts (Algazone Mx30) were treatments applied in the main plots, while the subplots received mineral fertilizer combinations. A randomized complete block design (RCBD) consisted of a factorial arrangement and three replications to evaluate the maize cultivar ‘Maha’s’ response in clay loam soil. In most growth and yield parameters, applying nitrogen-phosphorous fertilizer combinations and the foliar application of seaweed extract (4 ml L^-1) had a substantial effect. The interaction between the seaweed extract and nitrogen and phosphate fertilizers significantly improved leaf area, stem diameter, chlorophyll index in leaves, 500-grain weight, and biological and grain yields. The treatments with seaweed extract (4 ml L^-1) and the combination of 150 N + 50 P performed better for leaf area (55.48 cm² plant^-1), stem diameter (23.10 mm), chlorophyll index (48.54 SPAD), 500-grain weight (141.17 g), biological yield (357.56 g plant^-1), and grain yield (201.46 g plant^-1).

Keywords: Maize (Zea mays L.), seaweed extract, nitrogen and phosphorus fertilizers, growth and yield traits, chlorophyll index

Key findings: A significant improvement in growth and yield traits of maize resulted from the foliar application of seaweed extract (4 ml L^-1) in combination with nitrogen and phosphorus fertilizers.