| Abstrakt: |
The present work screened four factors (i.e., tillage, initial soil water content (IWC), freezing–thawing (F–T) and drying–wetting (D–W) cycles) to examine the Mollisols aggregate size distribution and stability. Soils were sampled from no-till (NT) and conventional tillage (CT) treatments in the 0–10 cm soil layer and conducted 0/3/6/11 F–T and D–W cycles. Three different IWC values were considered: 130, 230, and 330 g/kg, and our trials set up four aggregate size classes: larger aggregate size fractions (LWSA, >1.00 mm), medium aggregate size fractions (MWSA, 0.25–1.00 mm), small aggregate size fractions (SWSA, 0.106–0.25 mm), and particles (PA, < 0.106 mm); and the mean weight diameter (MWD) was used to analyze water-stable aggregate stability (WAS). Significant decrease of LWSA and WAS in NT was observed in the snowmelt stage, but the opposite results occurred during the crop growth period. In the simulated experiment, significant interactive effects of tillage and IWC on LWSA and WAS were observed in the F–T and D–W cycles, which showed that LWSA and WAS elevated as the F–T and W–D cycle numbers and IWC increased for both NT and CT treatments exhibited negative correlation with WAS. The greater amount of LWSA in NT was observed than CT in the F–T cycles, while the opposite results were in W–D cycles. The SWSA fraction had a negative relation with LWSA for NT treatment, and the MWSA fraction had a contrary variation with LWSA for CT treatment. In either tillage treatment, PA was not greatly affected. We therefore suggested to evaluate size distribution and stability of the Mollisols aggregates by including tillage, IWC, F–T and W–D cycles. [ABSTRACT FROM AUTHOR] |
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