Partial organic fertilizer substitution for chemical fertilizer has been proven to reduce the synthetic nitrogen (N) fertilizer requirement while maintaining or improving rice yield. However, little is known about the underlying physiological mechanisms of such an effect. Field trials were conducted to investigate the effect of organic fertilizer substitution for chemical fertilizer on rice yield and the source–sink relationship in two growing seasons. The treatments were as follows: no N fertilizer application (CK); farmers’ fertilizer practice (FFP); optimal chemical N management (OPT); and organic fertilizer substitution based on the OPT treatment (OPT-SN). Compared with treatments of chemical N fertilizer alone, rice yield was maintained in the OPT-SN treatment. The value of the sink–source difference in rice was positive during the grain filling period irrespective of the treatments, implying that the grain yield was source-limited. Although the effects on sink growth were similar among the different N addition treatments, organic fertilizer substitution improved source capacity by extending the duration of source activity when compared with treatments only containing chemical N fertilizer. The source–sink relationship was more balanced (lower sink–source difference) in the OPT-SN treatment relative to treatments of chemical N fertilizer alone, and a significant negative relationship between sink–source difference and grain yield was observed. Overall, organic fertilizer substitution could maintain grain yield by establishing a more balanced source–sink relationship during the grain filling period. Our findings clarify the positive effect of organic fertilizer substitution on source–sink balance and provide a basis for fertilization strategies to improve crop productivity.

已证明部分有机肥替代化肥可减少合成氮 (N) 肥料需求，同时保持或提高水稻产量。然而，人们对这种效应的潜在生理机制知之甚少。通过田间试验研究了有机肥替代化肥对水稻产量的影响以及两个生长季节的源库关系。处理如下：不施氮肥（CK）；农民施肥实践（FFP）；最佳化学氮管理（OPT）；基于OPT处理的有机肥替代（OPT-SN）。与单独施氮肥处理相比，OPT-SN处理保持了水稻产量。水槽的价值——灌浆期水稻源差异与处理无关，表明水稻产量是源限性的。尽管不同氮添加处理对库生长的影响相似，但与仅添加化学氮肥的处理相比，有机肥替代通过延长源活动持续时间来提高源容量。相对于单独施氮肥处理，OPT-SN 处理的源-库关系更加平衡（较低的库-源差异），并且库-观察来源差异和粮食产量。总体而言，有机肥替代可以通过在灌浆期建立更加平衡的源库关系来维持粮食产量。我们的研究结果阐明了有机肥替代对源库平衡的积极影响，并为提高作物生产力的施肥策略提供了基础。