Relationship between the percentage of clay with liquid limit, plastic limit and plastic index in four different soils texture class

The Atterberg limits and the Proctor compaction test parameters are related to agronomy with regard to compaction hazard for soils and tillage. This study was conducted to characterize the percentage of clay with consistency limits (liquid limit, LL; plastic limit, PL and plastic index, PI) of in four different soils texture class (clay, silty clay, silty clay loam and clay loam). The result revealed soil plasticity has direct correlation with percentage of clay. The consistency limits, and plasticity index (PI = LL - PL) were measured for the soil taken from the 0-20 cm layer. The LL varied from 38 to 63 in clay soil texture, 27 to 55 in silty clay, 21 to 44 in silty clay loam and 15 to 35 in clay loam texture. The PL varied from 13 to 34 in clay soil texture, 12 to 33 in silty clay, 10 to 27 in silty clay loam and 10 to 26 in clay loam texture. The lowest PI was recorded in clay loam texture. The results of this study showed that soil clay content significantly change Atterberg limits and plastic index. Soil clay content in all experimental soils significantly (p < 0.01) increased liquid limit (LL) plastic limit (PL), and plastic index (PI) values. The highest LL, PL and PI values were obtained in clay-textured soil. There was a significant relationship between the soil clay content and the Atterberg limits and plastic index. The positive relationship between soil clay content and PL, LL and PI was found to be significantly linear whereas the relationship with the soil sand content was significantly negative. Regression analysis for Atterberg limits in four soil texture class showed that the percentage of clay were important character on liquid limit, plastic limit and plasticity index.