Summary
This long-term field study quantifies how tillage intensity and nitrogen source affect soil structural stability using multiple complementary aggregate indices across three Great Plains sites. Intensive tillage (conventional and moldboard plough) reduced ASI, MWD and GMD by 8–47%, whilst manure addition increased these metrics by 33–73%, suggesting manure could offset tillage-induced structural degradation. The authors demonstrate that fractal dimension provides unique structural information not captured by traditional diameter-based indices and recommend considering all indices together in management decisions.
UK applicability
The findings are relevant to UK arable systems, particularly regarding no-till vs. conventional tillage comparisons and the structural benefits of organic amendment. However, the study's focus on intensive cropping systems in semi-arid Great Plains conditions (lower rainfall) may limit direct transferability to wetter UK clay and loam soils, where structural stability dynamics and management trade-offs may differ.
Key measures
Aggregate Stability Index (ASI), Mean Weight Diameter (MWD), Geometric Mean Diameter (GMD), Fractal Dimension (FD)
Outcomes reported
The study evaluated multiple soil aggregate indices (ASI, MWD, GMD, FD) to quantify soil structural development across three long-term field sites in the central Great Plains under different tillage (NT, RT, CT, MP) and nitrogen source treatments (mineral fertiliser vs. manure). Results showed intensive tillage reduced aggregate stability whilst manure addition substantially improved soil structure metrics.
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