Bioscience Methods 2025, Vol.16, No.6, 270-279 http://bioscipublisher.com/index.php/bm 2 76 6.3 Nitrogen-saving cultivation models and data analysis in South China’s double-cropping areas In the South China region where double-cropping rice is widely grown, people have long attempted to save nitrogen. The combination of methods like simplified nitrogen reduction cultivation (SNRP), close planting and delayed fertilization has a much more powerful actual effect than traditional approaches. SNRP can increase the yield by 23%, and it is not difficult to double the nitrogen fertilizer utilization rate by two or three times (Fu et al., 2023). There is also the strategy of close planting combined with nitrogen reduction and adding some backward transfer fertilization, which can increase the yield by 24% to 30% and the nitrogen utilization rate by 60% to 70%. Precision fertilization in green fat-rice rotation sounds meticulous, but the results are quite surprising - the amount of synthetic nitrogen used is reduced by one-third to two-thirds, and the nitrogen footprint is also reduced (Liang et al., 2023). From these examples, it can be seen that the key does not lie in relying on a single trick, but in the proper coordination of varieties, fertilizers and planting rhythms, which can enable the double-cropping rice system to achieve a win-win-win situation of "stable yield + high efficiency + low pollution". 7 Integrated Optimization of Variety Selection and Fertilization Strategy 7.1 Developing variety-specific fertilization recommendations Not all varieties can accept the same fertilization method without exception. Some hybrid rice varieties and high-yield varieties can better exert their potential when the nitrogen fertilizer application rate is controlled within the range of 180 to 225 kg N/ha, combined with water-saving irrigation (Zhu et al., 2024). But it doesn't mean that once the dosage is appropriate, everything else will go smoothly. Different fertilization methods result in different responses of varieties - for instance, some are suitable for deep application, while others perform better under fractional fertilization or controlled-release fertilization (Baral et al., 2020). Salt-tolerant rice varieties are another matter. They are quite sensitive to ammonium nitrogen fertilizers. With an appropriate planting density, their resistance to salt pressure can be further improved. So, to make reliable fertilization suggestions, one cannot merely look at the soil or climate; the variable of genotype must also be taken into account. Without targeted supporting plans, it is hard to talk about green and efficient development. 7.2 Interactions between variety and fertilizer on resource use efficiency Ultimately, how to apply fertilizer to a variety cannot be decided merely based on experience. The responses of different genotypes to fertilization methods can be described as "vastly different in style". For some varieties, when they are applied with slow-release fertilizers or deep fertilizers, the utilization rate of nitrogen fertilizers can increase sharply, and the yield will also rise accordingly. But with another variety, it might be more "responsive" to foliar spraying or fractional fertilization (Wang et al., 2022; Sajjad et al., 2024). When placed in different irrigation environments, the situation becomes even more complicated - for instance, under alternating dry and wet irrigation or shallow water conditions, some varieties can still achieve a "double improvement" in nitrogen fertilizer efficiency and water use efficiency. These differences are not merely superficial phenomena. Behind them, the mechanisms of crop absorption, transportation and distribution are at work (Lee et al., 2025). So, expecting "one management solution to solve all problems"? Obviously not realistic. To truly enhance the utilization rate of resources, it is necessary to find the "right" combination between varieties and management methods. 7.3 Comprehensive evaluation of high-yield and environment-friendly models To increase grain production without damaging the environment, relying on a single measure alone is far from enough. From the perspective of field practice, the combination of measures is the right solution - select high NUE varieties, and then combine the methods of controlled-release fertilizer, deep application, and multi-application fertilization. The yield has increased, the quality is guaranteed, and the environmental burden can also be reduced (Zhang et al., 2025). Moreover, this kind of "combined approach" is not only reflected in output efficiency, but also in sustainability. With precise fertilization and water-saving irrigation, even the "invisible" indicators such as soil health and greenhouse gas emissions have been optimized. This model, which takes into account both field management and ecological benefits, is much more reliable than the traditional approach and has laid a relatively stable foundation for sustainable rice production.
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