Soil Aggregates Features Under Different Tillage Systems in North China Plain

Tillage practices influence the aggregation and stability of soil aggregates. The objective of this study was to investigate the effects of different tillage treatments on soil aggregate characteristics. Soils were sampled from four depth intervals of No-tillage (NT), Rotary tillage (RT), and conventional tillage (Moldboard tillage, CT) treatments at the Luancheng Research Station in Hebei Province. Measurements of mean weight diameter (MWD), geometric mean diameter (GMD), proportion of macro-aggregates (R _0.25), and fractal dimension (D) were employed to characterize aggregate size distribution and stability. The results indicated that the NT treatment significantly increased the topsoil (0–5 cm) bulk density (BD), while the RT treatment increased BD in the 10–20 cm interval. The NT treatment had higher Macro-aggregate content (R _0.25), and a larger MWD and GMD than other treatments in the 0–10 cm layer, while RT showed no difference with CT. The wet sieving results showed that most of the aggregates were unstable. At 0–10 cm layer, the fractal dimension (D) of aggregates under NT was lower than it was under RT or CT. R _0.25 was positively linear correlated with MWD (R ² > 0.85), while D was negatively linear correlated with MWD, with R ² = 0.76. After four years, NT increased the aggregation and the stability of soil aggregates and bulk density, while intensive soil disturbance in RT and CT systems decreased the aggregation and stability, but maintained low bulk density in the upper layer (0–10 cm).