Bioscience Methods 2025, Vol.16, No.6, 270-279 http://bioscipublisher.com/index.php/bm 2 75 withstand such a reduction intensity (Wei et al., 2021; Wei et al., 2025). Not only in terms of yield, but also in terms of tillering number, effective tillering rate, and the number of spikers, NSV is more resilient, and even its carbon and nitrogen metabolism is more stable. However, if chemical nitrogen is partially replaced by organic fertilizers (such as cow dung and cake fertilizer), the nitrogen content in the soil can be significantly increased, which is beneficial for maintaining soil vitality in the long term (Wang et al., 2023; Zhou et al., 2024). In addition, some experiments also pointed out that as long as the nitrogen fertilizer dosage is controlled between 180-223 kg N/ha, nitrogen loss and greenhouse gas emissions can be significantly reduced while the yield approaches the maximum value (more than 95%) (Figure 2) (Xu et al., 2025). So, choosing the right variety and combining it with a reasonable fertilizer strategy can not only ensure production but also reduce environmental pressure. This is not just empty talk. Figure 2 The location of the study area (a) and the layout of the experimental plots (b) (Adopted from Xu et al., 2025) 6.2 Nitrogen reduction practices in major rice production areas of Northeast China The problem in Northeast China is more often due to "excessive use". The nitrogen fertilizer was heavily applied right from the start, but the output did not increase significantly. Instead, environmental problems emerged first. Recent experiments have offered some more "restrained" approaches, such as controlling the fertilizer application at 99 to 125 kg N/ha, combined with water-saving irrigation or appropriately increasing the planting density. As a result, not only did the harvest index increase, but the grain filling was also better, and the yield actually rose. There is a set of data that is quite illustrative: a 20% reduction in nitrogen fertilizer, a 32% increase in planting density, a 3% to 5% increase in yield, and the quality of the rice is not compromised (Dong et al., 2025). So, in places like Northeast China where "high-starting-point fertilization" is adopted, the way to improve is not just to "apply less", but to "apply less with a plan".
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