BM_2025v16n4

Bioscience Methods 2025, Vol.16, No.4, 204-217 http://bioscipublisher.com/index.php/bm 211 ordinary japonica rice, and the yield advantage was obvious. Under the nitrogen reduction treatment, the decline in its yield was also greater than that of some conventional japonica rice. This shows that high-yield hybrid rice such as "Yongyou 33" is more sensitive to nitrogen supply: sufficient nitrogen can maximize its hybrid advantage to achieve high yield, but insufficient nitrogen is more likely to result in small panicles and few grains, and a decline in yield. Therefore, for this type of variety, it is advisable to adopt a fertilization strategy of "promoting in advance and controlling in the later stage", that is, sufficient nitrogen supply in the early stage to promote tillering, appropriate nitrogen control in the later stage to prevent greed, and good water pipes and plant protection to reduce lodging and the occurrence of diseases and insects. Under reasonable management, indica-japonica hybrid rice can maintain good nitrogen efficiency at a higher yield level. According to Zhou et al. (2020)'s study of 24 "Yongyou" series varieties, one type of high-yield hybrid rice achieved both high yield and high nitrogen efficiency. Its total nitrogen absorption during maturity was only about 5% higher than that of ordinary types, but its yield was more than 13% higher. These varieties showed higher panicle number, panicle formation rate and late dry matter accumulation, and were able to transport more nitrogen to the panicle. By combining variety selection and fertilization regulation, the high yield potential and high nitrogen efficiency of hybrid rice can be taken into account to achieve "high yield and high efficiency". 5.2 Nitrogen uptake and utilization of conventional late japonica rice Compared with hybrid rice, conventional japonica rice varieties have slightly lower yield potential but more stable rice plant types, and their response to nitrogen fertilizer levels is relatively slow. Take two new high-quality late japonica varieties in Zhejiang, "Jiahe 567" and "Xiushui 1717", as examples: they can show higher nitrogen absorption and utilization capabilities and yield levels under moderate nitrogen input, and the marginal effect of excessive nitrogen application on yield is not as obvious as that of hybrid rice. According to the demonstration results in Jiashan County, under the conditions of unified fertilization management (pure nitrogen of about 15.4 kg/mu, one base fertilizer + one topdressing), the average per-mu yields of "Jiahe 567" and "Xiushui 1717" were about 620 kg and 600 kg, respectively, which was not much different from the treatment with increased nitrogen fertilizer. This shows that these conventional late japonica rice varieties have high nitrogen utilization efficiency and can maintain relatively ideal yields under less nitrogen supply. The mechanism may be that the plant type is more compact and the root system is more active, which can absorb soil nitrogen more fully; at the same time, the panicle structure and fruiting rate are more optimized, and the number of grains produced per unit nitrogen is higher (Huang et al., 2024). For example, Jiahe 567 has moderate tillering and high panicle rate, and the yield difference between the control nitrogen level and the 20% nitrogen reduction treatment is very small. For example, Xiushui 1717 has high-quality rice and strong stems, and still maintains a good fruiting rate and thousand-grain weight when nitrogen fertilizer is low. Conventional late japonica rice is more sensitive to excessive nitrogen fertilizer in terms of rice quality: studies have found that excessive nitrogen application will reduce the smoothness and taste of rice, while moderate reduction of nitrogen fertilizer is beneficial to improving the quality of high-quality japonica rice (Jiang et al., 2022). Therefore, for high-quality conventional rice such as Jiahe 567 and Xiushui 1717, a reasonable nitrogen fertilizer level should be determined based on the target yield to balance yield and quality. Conventional late japonica rice varieties show good nitrogen utilization "resilience" and can achieve a high nitrogen harvest index and fertilizer utilization rate under moderate nitrogen supply. This type of variety is suitable for promotion in nitrogen fertilizer reduction measures, which can reduce fertilizer input without significant loss of yield. 5.3 Compatibility analysis between varieties and fertilization strategies The optimal fertilization strategies for different rice varieties are different, and the matching (compatibility) of variety characteristics and fertilization measures is the key to achieving high yield and high efficiency. For high-yield hybrid rice, it should be emphasized to "apply nitrogen according to the variety", provide sufficient nitrogen according to its high biomass and large panicle characteristics, but at the same time avoid excessive nitrogen in the later stage. For example, for the Yongyou series of hybrid rice, the basal tillering fertilizer should be relatively sufficient to establish a sufficient number of panicles, and the panicle fertilizer should be appropriate

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