Changes in Rheological Properties of Four Contrasting Soils as Induced by Cultivation

Atterberg limits are rheological properties that command strong influence on the physical properties of soils and therefore, could be used as an indication of soil quality for long-term land use management systems of soils. Thus the study was under taken to evaluate changes in rheological properties of four contrasting soils as induced by cultivation. The four soils studied were Entisol, Ultisol and two Inceptisol; all collected from four different locations, in Nsukka area of Southeastern, Nigeria. The land use types considered were fallow and cultivated. Soil samples collected from 0-25cm depth were air-dried at room temperature and then were separated into five aggregate fractions, 5-2mm, 2- 1mm, 1-0.5mm, 0.5-0.25mm and < 0.25mm. Soils for the determination of consistency limit were further sieved using sieve N0. 36 (0.0045mm) to remove the coarse particles before being used to determine changes in their rheological properties due to cultivation, Two hundred grams (200g) of each sample were used for determination of Atterberg and Shrinkage limits. The result of the study showed that rheological properties of the soils were affected by cultivation. Cultivation decreased the value of plastic limit (PL) of IEh and ENsk, but increased the value of liquid limit (LL) and Plasticity Index (PI) of ENsk (45.6%, 23. 4%), IEh (34.5%, 14. 9%), and Iik (35.6%, 20.2%) in cultivated soils respectively relative to the fallow soils. The result of shrinkage limit and volumetric shrinkage (VS) limit values indicated that cultivation caused 10.71% and 40.49% increase in ENsk, IEh and 7.14% and 24. 9% increase in Iik respectively in cultivated soils relative to the fallow soils. From the result of this study, it is evident that cultivation affected the rheological properties of these soils through their variability in the Atterberg limits.