Characteristics of Biopores From Rice Root in Paddy Soil Under Long‐Term Different Fertilization

Soil biopores play a crucial role in enhancing crop root growth and resource acquisition in paddy soil and are influenced by different fertilization regimes. However, the mechanisms through which fertilization affects paddy field biopores via rice root morphology and soil properties remain poorly understood. This study aimed to assess the response of soil biopores derived from rice root to various long‐term fertilization in paddy soil using X‐ray computed tomography. Based on a 32‐year long‐term fertilization experiment, we selected four fertilization treatments for the soil column experiments: unfertilized (CK), chemical nitrogen and phosphorous fertilizers (NP), chemical N, P, and potassium fertilizers (NPK), and NPK with manure (NPKM). Findings indicated that total root volume, root length, surface area, and average diameter significantly increased in fertilized treatments compared to CK, with the highest values in NPKM. Long‐term inorganic fertilization (NP and NPK) had no significant impact on biopore volume, whereas NPKM significantly increased total biopore volume and bioporosity by 87.1%. NPKM also produced the highest mean weight diameters of soil aggregates (1.88 mm) and reduced bulk density (1.03 g cm −3 ). Compared to CK, the NPKM treatment increased soil organic carbon (SOC), NH 4 + ‐N, NO 3 − ‐N, available phosphorous (AP), and available potassium (AK) by 22.5%, 106.8%, 124.6%, 97.1%, and 32.4%, respectively, leading to higher enzyme activities related to carbon cycling (α‐glucosidase, β‐glucosidase, and β‐cellobiohydrolase). Structural equation modeling (SEM) revealed that soil physical properties and rice root directly enhanced biopore formation, while soil properties and enzyme activities indirectly influenced biopores by improving root growth. Overall, the prolonged application of inorganic fertilizer with manure increased biopores by enhancing soil structure, nutrient availability, and enzyme activity, while inorganic fertilization alone had no significant effect. These findings highlight the importance of manure in improving biopore formation and soil structure in paddy fields.