Effects of Nitrogen Fertilization at Heading Stage on Yield and Quality of Domestic Bread Wheat Cultivars

Nitrogen (N) fertilizer application increases protein concentration during the late stages of wheat growth. However, research on the timing and amount of N fertilizer application and their effects on flour quality in domestic cultivars for baking is limited. This study aimed to compare the yield and flour quality of domestic wheat cultivars Jokyoung and Baekkang, for baking based on the timing and amount of N fertilizer application. To determine the optimal timing of N fertilizer application at the heading stage, 3 kg/10a of N fertilizer was applied at one-week intervals between 14 days before and after heading. The timing of N fertilizer application did not influence spike number, grain number per spike, test weight, and yield; however, thousand-grain weight and gluten content were highest at seven days after heading (DAH). Subsequently, the yield and quality were evaluated based on the application of N fertilizer at 0, 3, 6, and 9 kg/10a at seven DAH. Increasing N fertilizer application at seven DAH led to an increase in protein content and gluten content. SDS-sedimentation values and loaf volume increased up to 6 kg/10a and then either decreased or remained constant. Dough development time decreased depending on the N application amount. Additionally, firmness decreased with higher N application levels. Significant differences were observed in glutenin and gliadin protein fractions based on amount of N application at seven DAH for both cultivars. Increased nitrogen fertilization led to a decrease in the proportion of high-molecular-weight glutenin subunits (HMW-GS) and an increase in low-molecular-weight glutenin subunits (LMW-GS), resulting in a decrease in the HMW/LMW-GS ratio. Additionally, gliadin composition changed with increased nitrogen fertilization, as the proportion of (α+β)-gliadin and ω-gliadin increased while the proportion of γ-gliadin tended to decrease. The evaluation of N fertilizer application timing and amount in this study is expected to be useful for N fertilization practices in these two domestic wheat cultivars for baking.