Estimating the influence of related soil properties on macro- and micro-aggregate stability in ultisols of south-central China

- Macro- and micro-aggregate stability were analyzed.
- Estimating the influence of related properties on macro- and micro-aggregate stability.
- Ald was the most important binding agent of the macro-aggregates.
- Clay was the main binding agent of the micro-aggregates.

BackgroundStable macro- or micro-aggregates are important for preventing soil degradation. The interactions among soil aggregates and stabilizing agents-like clay, soil organic matter (SOM), Fe, and Al oxides-are complex and have not been fully understood.MethodsEight ultisol samples were collected from the surface (0-10 cm) and subsurface layers (10-20 cm). The macro-aggregate stability was determined by wet sieving, and the micro-aggregate distribution was determined via particle size distribution analysis; however, no chemical dispersant (sodium hydroxide) was applied. Using the PLSR models, the main soil properties that affect macro-aggregate and micro-aggregate stability were estimated.ResultsAll soils were strongly acidic (pH 4.28-5.56) with low SOM content (< 20 g kg− 1). The dithionite-citrate-bicarbonate extractable Fed and Ald were the dominant forms in Fe and Al oxides, much greater than acid ammonium oxalate extractable Feo and Alo. For most soils, the percentage of > 5 mm aggregates was the highest, and the percentage of 2-1 mm aggregates was the lowest after wet sieving. Soil parent materials had a significant effect on the particle size distribution of the micro-aggregates. The stability of macro-aggregates and micro-aggregates from Quaternary red clay was stronger than that from Shale (p < 0.05). Regardless of the soil parent materials, the water stability of surface cropland soil macro-aggregates was significantly lower than that of the other land-use types, but the micro-aggregate stability exhibited no trend across different land use types.ConclusionAld was the most important binding agent of the macro-aggregates, and clay was the main binding agent of the micro-aggregates, followed by the Fed, Alo, CEC and SOM, while Feo was the weakest agent.