Objective This study aims to clarify the regulatory effects of different fertilization methods on soil aggregate stability in paddy fields, thereby providing a scientific basis for optimizing fertilization management practices, improving soil structure, and enhancing soil erosion resistance. Methods The paddy fields at the Zengcheng research base of South China Agricultural University were selected as the study area. Undisturbed soil samples from the surface layer (0—20 cm) and the subsurface layer (20—40 cm) of the paddy fields were collected under five fertilization treatments: no fertilization (CK), recommended fertilization (NPK), no phosphorus fertilizer (NK), no nitrogen fertilizer (PK), and organic fertilizer (OF). The water stability and fractal characteristics of soil aggregates were analyzed using the wet sieving method. Results (1) The content of >0.25 mm water-stable aggregates was highest in the OF treatment (69.27% in the surface layer and 67.32% in the subsurface layer), significantly higher than that in the NPK treatment (61.67% in the surface layer and 61.57% in the subsurface layer) and the CK treatment (60.52% in the surface layer and 58.30% in the subsurface layer). The mechanism lay in the input of fresh organic matter from organic fertilizer and the formation of humus, binding to soil clay particles through functional groups, thereby enhancing aggregate cohesion. The NPK treatment, due to insufficient continuous organic matter supplementation, resulted in reduced aggregate stability. Meanwhile, nutrient-deficient treatments without nitrogen (PK) or without phosphorus (NK) exhibited limited aggregate formation due to key nutrient deficiencies. (2) The mean weight diameter (MWD) and geometric mean diameter (GMD) of surface aggregates in the OF treatment increased by 13.7% and 22.6%, respectively, compared to the NPK treatment. Moreover, the stability of surface aggregates in all treatments was significantly superior to that of subsurface aggregates (p<0.05). (3) Fractal dimension (D) showed an extremely significant negative correlation with aggregate stability (r=-0.82, p < 0.01). (4) Soil organic matter content exhibited an extremely significant positive correlation with both the content of >0.25 mm aggregates and MWD (r values were 0.82 and 0.79, respectively, p<0.01), serving as a critical factor influencing aggregate stability. Conclusion Fertilization, particularly organic fertilizer application, can enhance soil organic matter content, promote large-aggregate formation, and improve aggregate water stability, thereby significantly improving the structural stability and erosion resistance of paddy soils in the red soil region of South China.
团聚体破坏率(Percentage of Aggregate Destr-uction, PAD)与R0.25的变化趋势相反。如图4所示,OF处理的PAD值最低(表层30.73%,下层32.68%),表明其团聚体在水中的稳定性最强。CK处理的PAD值最高(表层39.48%,下层41.70%)。NPK处理的PAD值也处于较高水平。
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