Seasonal Variability And Land Use Effects On Aggregate Stability, Shear Strength And Organic Matter Content Of An Ultisol

Ultisols of the tropics are characterised bylow crop productivity, severe degradation and variability in their properties due to inappropriate land use practices and seasonal changes. Knowledge of variability in soil properties is important for precision farming, adequate food production and environmental modeling. The major objective of this study was to evaluate the effect of season and land use on the studied properties. The experiment was factorially arranged in randomised complete block design (RCBD), with season, month of sampling and land use, serving as factors. Data were analysed using analysis of variance (ANOVA) and significant means were separated using least significant difference at 5% probability level. Bare fallow had the lowest shear strength (119.62 kN m(-2)), water stable aggregates (WSA) (33.34 %), soil organic matter (13.95 g kg(-1)), and bulk density (1.40 g cm(-3)). Soil under bush fallow had the highest shear strength (136.95 kN m(-2)) andWSA (38.00 %), and the least silt content (89.35 g kg(-1)). The shear strength, organic matter and aggregate stability varied moderately (C.V=16.89, 20.26 and 38.43%, respectively). Significant interactions between the season and land use were noted in organic matter content only. Seasonal variations affected shear strength, organic matter, and bulk density significantly (P=0.05).