【目的】研究头季机收后同一时期内不同时间施用叶面氮肥(FNF)对再生季水稻生理特性、产量和品质的影响，为再生稻增产提质提供科学依据。【方法】头季稻机收后，在高肥力(HF)和低肥力(LF)田块采用大田裂区双因素试验设计。其中，碾压状况为主区，包括碾压和非碾压两个处理；FNF施用时间为副区，包括机收后当日喷施清水(CK)，以及机收后1 d(D1)、3 d(D3)、7 d(D7)喷施FNF，测定再生季生理特性指标、产量和品质，阐明叶面施氮时间对再生季稻米产量及品质的影响。【结果】FNF能显著提高再生季叶片SPAD、干物质量、叶面积指数和有效穗数。在HF和LF两种条件下，FNF均能通过提高有效穗数进而提高产量25.6%~82.8%，非碾压区不同FNF喷施时间处理间无显著差异，但是有效穗数都较CK显著增加16.7%~30.6%，产量显著增加25.6%~36.7%。碾压区随着喷施时间的推迟增产效果逐渐降低，D1处理后在两种肥力条件下有效穗数分别显著提高61.5%和62.5%、产量分别显著提高74.9%和82.8%。FNF主要通过提高整精米率和降低垩白率提高再生季稻米品质，与CK相比，非碾压区施FNF处理整精米率显著提高9.5%~17.8%，垩白率显著降低8.1%~15.3%；碾压区施FNF处理整精米率显著提高15.0%~17.9%，垩白率显著降低9.2%~15.7%。【结论】头季机收后施叶面氮肥能有效提高再生季产量和品质，碾压区受喷施时间影响明显，以机收后当日喷施效果最好；非碾压区受喷施时间影响不明显，机收后7日内均可喷施。

【Objective】This study aims to investigate the effects of foliar nitrogen fertilizer (FNF) application at different times within the same period after mechanical harvesting of the main crop on the physiological characteristics, yield, and quality of ratoon rice, providing a scientific basis for increasing yield and improving quality of ratoon rice. 【Method】After the mechanical harvesting of the main crop, a field split-plot two-factor experiment was conducted in high-fertility (HF) and low-fertility (LF) fields. The main plots were assigned to rolling and non-rolling conditions, while the subplots were assigned to different FNF application times: spraying clean water on the day of harvesting (CK), and spraying FNF at 1 day (D1), 3 days (D3), and 7 days (D7) after harvesting. The physiological characteristics, yield, and quality of ratoon rice were measured to elucidate the effects of foliar nitrogen application timing on yield and quality. 【Result】The results showed that FNF significantly increased the SPAD value, dry matter weight, leaf area index, and effective panicle number of ratoon rice. Under both HF and LF conditions, FNF increased yield by 25.6%-82.8% by improving the effective panicle number. In the non-rolling area, no significant differences were observed among different FNF application timings, but all treatments significantly increased effective panicle number by 16.7%-30.6% and yield by 25.6%-36.7% compared to CK. In the rolling area, the yield enhancement effect gradually decreased with delayed FNF application. Under the D1 treatment, the effective panicle number significantly increased by 61.5% and 62.5%, and yield significantly increased by 74.9% and 82.8% under the two fertility conditions, respectively. FNF primarily improved the quality of ratoon rice by increasing the head rice rate and reducing the chalkiness rate. Compared to CK, in the non-rolling area, FNF significantly increased the head rice rate by 9.5%-17.8% and significantly reduced the chalkiness rate by 8.1%-15.3%; in the rolling area, FNF significantly increased the head rice rate by 15.0%-17.9% and significantly reduced the chalkiness rate by 9.2%-15.7%. 【Conclusion】Foliar nitrogen fertilizer application after mechanical harvesting of the main crop effectively increases the yield and quality of ratoon rice. In rolling areas, the application timing significantly affects outcomes, with the best results achieved when spraying on the day of harvesting. In non-rolling areas, the application timing has no significant effect, and FNF can be applied within 7 days after harvesting.