Organic-inorganic fertilization has been proven to maintain sustainable rice production. However, the chemical nitrogen (N) fertilizer reduction and its underlying mechanisms have not been revealed under organic-inorganic fertilization. The objective of this study was to quantify how organic-inorganic fertilization affected rice yield and the source-sink relationship during grain filling. A two-year field experiment was conducted during the rice growing seasons of 2021 and 2022, with two organic fertilizer levels (-M, 0 kg ha and +M, 3000 kg ha), and five N rates (N0: 0 kg ha, N90: 90 kg ha, N180: 180 kg ha, N270: 270 kg ha, N360: 360 kg ha). Rice yield and yield components, agronomic N use efficiency (AE), leaf area index (LAI), chlorophyll content, and source-sink traits were examined. Compared with -M treatment, organic-inorganic fertilization increased rice yield. Rice yield for N180 + M was comparable to that for N270 and N360 in two years, while AE significantly increased 22.29% compared to N360. LAI and SPAD value were also increased under organic-inorganic fertilization. The rice sink growth and source activity increased with the increase of N rate and organic fertilization. Compared with -M treatment, organic-inorganic fertilization showed higher sink growth and source capacity. Rice yield was source-limited under -M and +M treatments, while organic fertilizer application could increase the source/sink ratio. Meanwhile, we found that the source/sink ratio was significantly positively correlated with rice grain yield. Partial least squares path modeling (PLS-PM) showed that organic-inorganic fertilization optimized source-sink balance by increasing source capacity and sink growth, thereby increasing the rice yield. The high rice yield of organic-inorganic fertilizer over N fertilizer could be explained by its higher sink growth and source capacity. Considering comprehensively yield, AE, and source-sink balance, a combination of N rate of 180 kg ha and organic fertilization of 3000 kg ha was the optimal organic-inorganic fertilization management practice. The study provides a scientific basis for chemical N reduction in rice production and contributes to the promotion of agriculture sustainable development.

中文翻译：

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最佳有机-无机施肥通过灌浆期间源库平衡提高水稻产量

有机-无机施肥已被证明可以维持可持续的水稻生产。然而，有机-无机施肥下化学氮肥的减少及其潜在机制尚未揭示。本研究的目的是量化有机-无机施肥如何影响水稻产量以及灌浆过程中的源库关系。在2021年和2022年的水稻生长季节进行了为期两年的田间试验，采用两种有机肥水平（-M，0千克公顷和+M，3000千克公顷）和五种氮肥施用量（N0：0千克公顷， N90：90 公斤公顷，N180：180 公斤公顷，N270：270 公斤公顷，N360：360 公斤公顷）。研究了水稻产量和产量构成、农艺氮素利用效率（AE）、叶面积指数（LAI）、叶绿素含量和源库性状。与-M处理相比，有机-无机施肥提高了水稻产量。 N180+M两年内的水稻产量与N270和N360相当，而AE较N360显着增加22.29%。有机-无机施肥下 LAI 和 SPAD 值也有所增加。水稻库生长和源活动随着施氮量和有机肥的增加而增加。与-M处理相比，有机-无机肥显示出更高的库生长和源容量。 -M和+M处理下水稻产量受源限制，施用有机肥可提高源库比。同时，我们发现源库比与水稻产量呈显着正相关。偏最小二乘路径模型（PLS-PM）表明，有机-无机施肥通过增加源容量和库增长来优化源库平衡，从而提高水稻产量。有机无机肥比氮肥的水稻产量高可以解释为它具有更高的库增长和源容量。综合产量、AE及源库平衡等因素，施氮量180 kg·ha+有机肥3000 kg·ha组合为最佳有机无机肥管理措施。该研究为水稻生产化学减氮提供科学依据，为促进农业可持续发展做出贡献。