Maize is widely cultivated on sloping farmland in karst regions, yet the isolated effect of its aboveground structure on soil erosion remains unclear. This study used artificial maize plants and simulated rainfall experiments to quantify how aboveground structure of maize affects runoff, erosion, and rill morphology in the absence of root protection. Eighteen treatments combining varying slope gradients (5 degrees, 15 degrees and 25 degrees), rainfall intensities(60 and 90 mm/h), soil bulk densities (1.0 and 1.2 g/cm(3)), and soil aggregate sizes (<2 and < 5 mm) were tested with and without maize cover. Results showed that maize significantly shortened runoff initiation time (by 46-84%), increased runoff yield up to 4.4 times and elevated sediment yield (up to 15.2 times) compared to bare soil. The funnel effect of canopy, which concentrates rainfall into stemflow, was the dominant controlling factor (importance score > 47%). This effect was strongest for runoff initiation under small soil aggregates and gentle slopes, but strongest for sediment yield under large soil aggregates and steep slopes. Notedly, rill erosion occurred only under maize, with morphology varying by slope and soil bulk density. Gentle slopes and high soil bulk density favored wide, shallow rills, promoted lateral channel expansion. These findings reveal that maize aboveground structure can substantially amplify erosion risk and trigger concentrated flow erosion. Therefore, management strategies for sloping maize cultivation should include conservation measures to mitigate the hydrological amplification caused by stemflow concentration and to suppress rill formation, especially in areas where root protection is absent or degraded.