Triticeae Genomics and Genetics, 2025, Vol.16, No.2, 92-100 http://cropscipublisher.com/index.php/tgg 95 4.3 Optimization of density–nitrogen combinations for yield maximization For wheat to grow well and yield a high yield, it is also necessary to use nitrogen fertilizer appropriately. The planting density and fertilization methods should be well-matched. Many studies have pointed out that the most ideal effect is achieved by using a medium or slightly higher density and combining it with fractional fertilization (Dong et al., 2020; Wang et al., 2023). For instance, research has found that when the planting density increased from 750,000 plants per hectare to 3.36 million plants and the nitrogen fertilizer application was 290 kilograms, both the yield and nitrogen utilization rate reached the optimal level (Yang et al., 2019). When some people were studying weak-gluten wheat, they found that if 3 million plants were planted per hectare and 48.6 kilograms of fertilizer were applied, it could also perform well (Zhou et al., 2024). These methods can regulate the number of tillers, making the ears grow better and also contribute to the accumulation of dry matter. In this way, the output can be increased and the use of nitrogen fertilizer will be more efficient. Therefore, if you want to achieve high wheat yields and avoid wasting nitrogen fertilizer, the density and fertilization must be well balanced. With a slightly higher density and well-controlled fertilization methods, not only can the yield be maintained, but also waste can be reduced, the quality of grains can be improved, and it is more environmentally friendly. 5 Agronomic and Physiological Trait Evaluation 5.1 Plant height, tillering, and leaf area index Sowing density and nitrogen application rate will directly affect the plant height and tillering number of wheat. When 300 to 400 grains are sown per square meter, the number of tillers in the field will increase, and the final number of ears formed will also rise. Although this might slightly reduce the number of grains per spike, on the whole, the total output can still be increased. If nitrogen is applied in addition, the tillers will grow faster, the leaves will become larger, the leaf area index will increase, and the photosynthetic efficiency will be higher. This will make the plants grow more vigorously and have a larger biomass (Novruzov and Allahverdiyev, 2023). However, the height of plants is not only determined by density and nitrogen fertilizer, but also related to the variety and weather. For some wheat varieties, under high-density planting and excessive fertilization, the plant height will increase significantly and the flag leaves will also become longer. 5.2 Harvest index and nitrogen uptake efficiency If the sowing time is slightly later and nitrogen is applied in reasonable portions, the harvest index can increase by 5% to 7%, indicating that more nutrients are used on the grains (Lachutta and Jankowski, 2024). An appropriate amount of nitrogen fertilizer can promote nutrient accumulation and enhance the efficiency of nitrogen absorption and utilization. Generally speaking, when there is more nitrogen fertilizer, the grain yield and protein content will be higher (Ivicet al., 2021; Farooq et al., 2024; Li et al., 2025). However, different varieties performed differently. Some varieties had a higher nitrogen utilization rate and better yield performance under the condition of applying more nitrogen (Desai et al., 2024). 5.3 Lodging resistance and spike number per unit area As long as the sowing density is appropriate and the fertilization method is used correctly, the number of ears per square meter can be increased. When there are more ears, the yield will naturally be higher. This is one of the key factors affecting output. However, if they are planted too densely or too much fertilizer is used, the plants may grow too tall and are prone to toppling over. Especially when encountering varieties that are not resistant to toppling or when the fertilizer is not evenly spread, the situation will be even worse. Studies have shown that sowing 400 seeds per square meter and applying nitrogen fertilizer in stages yields the best results. This approach can increase production while minimizing the risk of overturning (Novruzov and Allahverdiyev, 2023; Lachutta and Jankowski, 2024). Besides, wheat with thick stems is less likely to fall over than thin ones. The thickness of the stem is also related to the density of the species and the type of variety (Pinheiro et al., 2019). 6 Case Studies: Field Implementation Across Regions 6.1 North China Plain: moderate density with split nitrogen application In the experiments in the North China Plain, it was found that medium-density sowing had a good effect. For instance, it would be appropriate to plant 300 to 400 seeds per square meter. Nitrogen fertilizer should not be
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