DOI: https://doi.org/10.36347/sajb.2026.v14i11.002

Pages: 754-765

Drought stress promotes the overproduction of reactive oxygen species (ROS), causing oxidative damage that limits maize growth and productivity. This study evaluated the effects of foliar-applied nano-biochar and sulphur on oxidative stress and antioxidant defense in maize (Zea mays L. cv. FH-1046) under drought. A pot experiment was conducted in a completely randomized design with two moisture regimes (control, 75–80% field capacity; drought, 35–40% field capacity) and three foliar treatments (distilled water, 3% nano-biochar, 12 mg L⁻¹ sulphur), with five replicates. Foliar sprays were applied 50 days after emergence, and leaf biochemical traits were measured 15 days later. Drought increased hydrogen peroxide (H₂O₂) content by 24% on average (P < 0.001), but the increase was confined to sulphur-treated plants (765.9 vs. 491.3 nmol g⁻¹ FW under well-watered conditions). Sulphur increased superoxide dismutase activity by 32% relative to the water spray, whereas nano-biochar increased peroxidase activity under drought by 83%. Drought induced a 4.6-fold increase in ascorbate peroxidase activity in unsprayed plants, but not in plants sprayed with nano-biochar or sulphur, and both sprays lowered total phenolics, mainly under well-watered conditions. Malondialdehyde, ascorbic acid, soluble sugars and free amino acids were not significantly affected. Neither spray reduced H₂O₂ or malondialdehyde, so these results do not demonstrate improved oxidative status or drought tolerance. The effects of foliar nano-biochar and sulphur on antioxidant responses were trait-specific and depended on water availability, and their consequences for growth and yield require further testing.