Molecular Soil Biology 2025, Vol.16, No.5, 265-271 http://bioscipublisher.com/index.php/msb 268 5 Timing and Method of Nitrogen Application 5.1 Effect of split application and topdressing During the growth of wheat, applying nitrogen several times is more effective than applying it all at once, especially after the booting stage, which is very helpful for yield and quality. Global studies have found that this practice can increase the protein, wet gluten and dough stability in the grain, and cause less yield loss than a single fertilization (Wu et al., 2022). For example, some studies suggest applying half of the fertilizer at the time of emergence and half at the tillering stage; some choose to apply fertilizer twice at the tillering stage and the booting stage, which can increase both yield and protein content. Which one is better depends on the local climate and soil conditions (Derebe et al., 2022). Topdressing before spikelet differentiation can also improve the development ability of the spike, thereby increasing yield (Aryan et al., 2024). In addition, split fertilization can also reduce the loss of nitrogen fertilizer, especially when using water-saving irrigation, this method can improve the utilization efficiency of nitrogen fertilizer (Zhang et al., 2022). 5.2 Comparison between deep placement and surface application The method of fertilization can also affect wheat growth and the amount of weeds. Compared with spreading fertilizer on the surface, applying nitrogen fertilizer 10 cm deep between crop rows, such as strip fertilization or spot fertilization, can make wheat grow better and reduce weeds. Deep nitrogen fertilizer allows wheat to absorb more nitrogen, while weeds grow less and are less likely to spread seeds, which is more conducive to establishing an efficient and sustainable production system. 5.3 Impact of controlled-release vs. conventional urea Controlled-release nitrogen fertilizers, such as coated urea, have many advantages over ordinary urea. They can release nitrogen slowly, which is more in line with the absorption rhythm of wheat and is not easy to cause waste (Wang et al., 2023). Studies have found that if controlled-release fertilizers are used, the amount of fertilizer applied is increased, or a second topdressing is chosen after heading, both yield and quality are usually better, especially in medium-textured soils and relatively moist environments. 6 Case Studies: Nitrogen Response in Selected Wheat Varieties 6.1 Nitrogen fertilizer regulation experiment of high-yield strong-gluten varieties Some high-yield strong-gluten wheat varieties respond significantly to nitrogen fertilizer. There are obvious differences in the ability of these varieties to absorb and use nitrogen, which is mainly determined by genetics (Mahjourimajd et al., 2016; Ivić et al., 2021). For example, some varieties can use nitrogen better under appropriate fertilization conditions, and both yield and quality are improved, which means that their "Nitrogen Efficiency Comprehensive Score (NECS)" is relatively high (Ding et al., 2023). This variety has the most obvious yield increase effect under high nitrogen application rates, and their genetic background supports faster nitrogen absorption and protein accumulation. For farmland that pursues high yield and high-quality strong gluten, this variety is very suitable for intensive management. 6.2 Quality performance of medium-gluten varieties under different nitrogen concentrations The yield and quality of medium-gluten wheat are greatly affected by nitrogen fertilizer, and different varieties respond differently (Ivić et al., 2021). Through field trials in different seasons, it was found that these varieties can be divided into several groups. Some varieties have stable yields within a certain range of nitrogen application, while others are very sensitive to changes in fertilizer application. The researchers also found gene loci related to nitrogen response in these varieties, which can be used to guide breeding. By selecting these genes, nitrogen utilization efficiency can be improved and the varieties can be more adaptable to different fertilization schemes (Ding et al., 2023). 6.3 Low-nitrogen environmental adaptability and nitrogen-saving potential of weak-gluten varieties Weak-gluten wheat generally does not pursue high yield or high protein, but pays more attention to nitrogen utilization efficiency and stress resistance (Figure 2) (Büchi et al., 2016; Yan et al., 2021). Some varieties can still produce stable output with little nitrogen fertilizer, showing good low-nitrogen adaptability. For example,
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