Effects of Conservation Tillage on Soil Structure and Bulk Density under Dryland

  Objective  This paper aims to clarify the effects of exogenous organic matter, tillage methods and their interactions on the changes of soil bulk density and physical indicators of aggregate characterization.

  Method  Relying on the National Agricultural Environment Jinzhong Long-term Cultivation Observation Platform in Semi-humid and Arid Areas, 8 tillage patterns were carried on, including no-tillage (NT), subsoiling (SU), rotary tillage (RT), tillage (CT) and under the coupled action of tillage and straw, no-tillage + Straw mulching (NTS), subsoiling + straw returning (SUS), rotary tillage + straw returning (RTS), ploughing + straw returning (CTS), and continuous corn cropping was for 5 consecutive years. The effects of tillage methods, fertilization and soil improvement combined with straw returning measures were discussed by measuring and comparing soil water-stable aggregates (WSA) and bulk density (BD).

  Result  ① Compared with CT, the mean weight diameter (MWD), geometric mean diameter (GMD) and > 0.25 mm aggregate content (R_0.25) of NT and SU soil water-stable aggregates were significantly increased (31.94%, 36.61%; 23.29%, 26.09%; 14.42%, 12.63%). ② Compared with CT, the effects of NT, SU and RT on soil BD were gradually weakened with the increase of soil depth in the vertical direction of soil layer. The coupling effect of straw and tillage has a random distribution on BD in 0 ~ 40 cm soil, RTS was the smallest, followed by SU. The ascending order of BD in 0 -10 cm topsoil was: NTS, RTS, SUS, CTS. Compared with CTS, the BD of NTS and RTS decreased significantly by 21.07% and 15.78%. ③ Correlation analysis showed that MWD, GMD and aggregate content > 2 mm had a significant positive correlation between them. In addition, NT and RT, BD were significantly negatively correlated with MWD, GMD and aggregate content > 2 mm.

  Conclusion  SU is as an important tillage measure to improve the physical properties of loamy clay in dry land. Continuous implementation of this tillage can not only promote the formation of soil water-stable aggregates, but also help to enhance the stability of aggregates, and also reduce the soil bulk density to a considerable extent. So it is recommended to consider SU as a universal farming promotion in the study area.