The Effects of External Applications at Different Nitrogen Doses on Yield and Yield Components of Some Bread Wheat Cultivars

As a globally dominant cereal, wheat (Triticum aestivum L.) plays a pivotal role in food security and agricultural sustainability. This study assessed the interactive effects of varying nitrogen rates and external treatments on yield-related traits in selected bread wheat cultivars. Field trials were carried out during the 2021–2022 growing season in Bafra (Samsun province, Türkiye), under controlled agronomic practices. Two bread wheat cultivars (Altındane and Pandas), five nitrogen doses (0, 8, 16, 24, and 32 kg da⁻¹), and two external applications (100 mM glycine betaine and 40 μM cytokinin) were evaluated using a split-split plot design with three replications. The results indicated that glycine betaine application significantly enhanced plant height and spike length. Cytokinin application (zeatin) positively affected main stem thickness, spike length, kernel yield, number of spikes per square meter, and thousand kernel weight, and demonstrated a superior performance compared to other treatments and the control group. In particular, under the highest nitrogen dose (32 kg da⁻¹), glycine betaine increased grain yield by 8%, while zeatin application led to a 21% improvement compared to the control. Overall, the findings suggest that exogenous applications hold substantial potential for improving kernel yield and yield components in bread wheat cultivation.