Fertilization Weakens the Ecological Succession of Dissolved Organic Matter in Paddy Rice Rhizosphere Soil at the Molecular Level

Dissolved organic matter (DOM) is involved in numerous biogeochemical processes, and understanding the ecological succession of DOM is crucial for predicting its response to farming (e.g., fertilization) practices. Although plentiful studies have examined how fertilization practice affects the content of soil DOM, it remains unknown how long-term fertilization drives the succession of soil DOM over temporal scales. Here, we investigated the succession of DOM in paddy rice rhizosphere soils subjected to different long-term fertilization treatments (CK: no fertilization; NPK: inorganic fertilization; OM: organic fertilization) along with plant growth. Our results demonstrated that long-term fertilization significantly promoted the molecular chemodiversity of DOM, but it weakened the correlation between DOM composition and plant development. Time-decay analysis indicated that the DOM composition had a shorter halving time under CK treatment (94.7 days), compared to NPK (337.4 days) and OM (223.8 days) treatments, reflecting a lower molecular turnover rate of DOM under fertilization. Moreover, plant development significantly affected the assembly process of DOM only under CK, not under NPK and OM treatments. Taken together, our results demonstrated that long-term fertilization, especially inorganic fertilization, greatly weakens the ecological succession of DOM in the plant rhizosphere, which has a profound implication for understanding the complex plant-DOM interactions.