ABSTRACT Hard Red Spring (HRS) wheat is a high-protein class prized for its nutritional value and functional properties in whole grain products. While nitrogen (N) fertilization is known to affect yield and protein content, its influence on antioxidant activity and antinutritional factors remains less explored. This study examined the effects of three N application rates (0, 100 and 150 lb/acre) on grain composition, antioxidant capacity and phytic acid content in three HRS wheat varieties grown at multiple locations in North Dakota and Minnesota. Antioxidant capacity was evaluated via total phenolics, flavonoids and radical scavenging assays (DPPH, ABTS, FRAP), while phytic acid was measured as an indicator of antinutritional potential. Application of 150 lb/acre N significantly increased grain protein content (20-24%, p 0.05) and enhanced antioxidant activity, with DPPH, ABTS, and FRAP values rising by 32%, 42% and 82%, respectively, relative to the control. These increases were associated with elevated levels of free (63%) and bound (53%) phenolics, as well as greater flavonoid accumulation. In contrast, phytic acid content declined significantly, from 8.5 to 5.5 mg/g (p 0.05), and was strongly negatively correlated with N rate (r = -0.8). Protein content, phenolics, flavonoids, antioxidant activity, and phytic acid levels were all significantly affected by genotype (G), environment (E), and G × E interactions. These findings suggest that optimized nitrogen fertilization can simultaneously improve grain protein and antioxidant properties while reducing antinutritional compounds. This targeted agronomic approach offers a promising strategy for producing healthier, nutrient-rich wheat under diverse genotype-environment conditions.
HOQUE et al. (Tue,) studied this question.