TITLE:
Shaking Speed and Depth Effects on Wet-Sieved Aggregate Stability under Arable, Cocoa and Oil Palm Soils
AUTHORS:
Joseph Asare, Hope Setsoafia Kwabena Dimakor, Philip Kwaku Kokonu, Seth Ofori
KEYWORDS:
Aggregate Stability, Revolutions Per Minute, Soil Organic Carbon, Tropical Soil, Wet Sieving
JOURNAL NAME:
Open Access Library Journal,
Vol.13 No.11,
November
11,
2026
ABSTRACT: Soil aggregate stability, a key indicator of structural quality, is commonly assessed by wet sieving, yet the shaking speed applied is rarely standardized for tropical soils. This study evaluated wet-sieved aggregate stability of soils under arable, cocoa and oil palm land use at two depths (0 - 15 and 15 - 30 cm) on the Kumasi Series, Ghana, testing whether 30, 40 and 60 revolutions per minute (rpm) produced values statistically comparable to the conventional 50 rpm standard. Composite samples were analyzed for particle size, bulk density, organic carbon, pH, available phosphorus, exchangeable bases and porosity, and aggregate stability was determined by the modified Kemper and Rosenau (1986) method at each speed. Stability was higher in topsoils (95.9% - 98.5%) than subsoils (92.3% - 97.5%) and declined progressively with increasing rpm. Paired t-tests showed that 30 and 40 rpm did not differ from the 50-rpm standard on the sandier arable and cocoa topsoils, whereas 60 rpm produced significant departures on most soils, particularly the oil palm topsoil (t = 26.0, P = 0.0015). Stability correlated positively with organic carbon and negatively with exchangeable sodium, higher in the clay-enriched subsoils. Lower shaking speeds (30 - 40 rpm) are adequate substitutes for the 50-rpm standard on sandy topsoils, whereas clay-rich soils require the higher speed to fully express aggregate breakdown; shaking speed should be reported explicitly when comparing aggregate stability data across tropical soil studies.