Divergent responses of aggregate stability to long-term mineral and organic amendments between upland and paddy soils

Purpose Aggregate stability is important for soil architecture; however, the specific response to long-term fertilization in upland and paddy fields are unknown. Here, we studied this issue in two adjacent subtropical upland and paddy soils under > 3 decades of mineral and organic fertilizations. Materials and methods Soil aggregate distribution was measured by wet sieving method. Three aggregate stability indices, mean weight diameter (MWD), geometric mean diameter (GMD), and percentage of water stable aggregates (WSA), were calculated. The stabilizing agents including root biomass, soil organic matter (SOM), and polysaccharides were measured, in which the chemical composition of SOM was measured by pyrolysis–gas chromatography-mass spectrometry (Py-GC/MS). Results and discussion In the upland soil, only manure amendment improved soil aggregation: large macro-aggregates (> 2 mm) increased, whereas mineral fraction (