Molecular Soil Biology 2025, Vol.16, No.4, 162-174 http://bioscipublisher.com/index.php/msb 163 This research aims to explore and develop strategies to enhance nitrogen use efficiency in rice, focusing on both agronomic practices and genetic improvements. The study will explore the role of nitrogen in rice growth, challenges in nitrogen application, and potential solutions to improve NUE, in an effort to provide comprehensive insights on optimizing nitrogen use in rice cultivation, ultimately promoting sustainable agricultural development and global food security. 2 Current Nitrogen Use Practices in Rice Farming 2.1 Conventional nitrogen fertilization methods In rice cultivation, conventional nitrogen (N) fertilization methods typically involve the application of nitrogenous fertilizers in various forms such as urea, ammonium sulfate, and nitrate-based fertilizers. The application rates of these fertilizers can vary significantly depending on the region, soil type, and specific crop requirements. Generally, farmers apply nitrogen fertilizers at rates ranging from 100 to 300 kg N/ha, with the timing of application being crucial to maximize nitrogen use efficiency (NUE) and crop yield. Commonly, nitrogen is applied in multiple split doses: a basal dose before or at the time of planting, followed by top-dressings at critical growth stages such as tillering and panicle initiation (Lee, 2021; Shrestha et al., 2022) (Figure 1). Figure 1 A farmer manually applying nitrogen fertilizer in a paddy field, illustrating conventional nitrogen management practices in rice farming. This reflects the common split-application method, where nitrogen is applied during key growth stages such as tillering to enhance nitrogen use efficiency (NUE) and crop yield (Photo from Zhigang Fu) The forms of nitrogen used in rice farming also play a significant role in determining the efficiency of nitrogen uptake by the plants. Conventional methods often involve surface broadcasting of prilled urea, which is prone to significant nitrogen losses through volatilization, leaching, and runoff. To mitigate these losses, some farmers have adopted deep placement techniques, where nitrogen fertilizers are placed deeper in the soil, closer to the root zone, thereby enhancing nitrogen availability and reducing losses (Baral et al., 2020; Khalofah et al., 2021). Despite these efforts, the overall NUE in conventional rice farming remains relatively low, necessitating the exploration of more efficient fertilization strategies. 2.2 Global trends in nitrogen use Globally, nitrogen application practices in rice farming exhibit considerable regional differences, influenced by factors such as local agronomic practices, soil fertility, and economic constraints. In developed countries, precision agriculture techniques and advanced fertilization methods are increasingly being adopted to optimize nitrogen use and minimize environmental impacts. For instance, the use of slow-release fertilizers and nitrification inhibitors is becoming more common, helping to improve NUE and reduce nitrogen losses (Ding et al., 2020; Wang et al., 2022).
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