X‐Ray CT Analysis of Soil Pore Structure, Connectivity and Hydraulic Responses to Micro‐Nanobubble Aerated Drip Irrigation

ABSTRACT Soil pore network architecture is fundamental to rhizosphere functioning. This study employed high‐resolution X‐ray computed tomography (CT) to quantify rhizosphere pore structure, spatial distribution, connectivity and hydraulic function in greenhouse tomato across two consecutive growing seasons (S1 and S2) under five micro‐nanobubble (MNB) aeration scheduling treatments: nonaerated control (CK), early aeration (AE), reproductive aeration (AR), late aeration (AL) and continuous aeration (AC). CT‐derived parameters included void ratio, pore morphology, nearest neighbour index (NNI), fractal dimension, absolute permeability and pore‐throat characteristics. AC produced the greatest improvements in the void ratio and pore area across both seasons. AR recorded the highest pore count in Season 1 (1.45 × 10 5 ) and NNI in Season 2 (6.9), indicating concentrated root–bubble interactions during peak oxygen demand. At the end of S1 and S2, the absolute permeability under AC was 8.6 and 18.9 μm 2 , respectively, compared with 4.3 and 0.7 μm 2 under CK. Because CT sampling was destructive and different soil blocks were collected at the end of each season, these values represent season‐specific cross‐sectional contrasts rather than longitudinal changes in the same soil core. Overall, growth‐stage MNB aeration was associated with distinct end‐of‐season rhizosphere pore‐network characteristics, supporting precision oxygen management in greenhouse SDI systems.