Impact of organic material incorporation with soil in relation to their shear strength and water properties

A b s t r a c t. A laboratory experiment was conducted to determine the quantitative effects of incorporating groundnut haulms, cow dung and chicken dung on hydraulic properties of compacted sandy loam, clay loam and clay soils. The consistency limits, shear strength, water retention and hydraulic conductivity of the three soil textures were measured. Groundnut haulms, cow dung and chicken dung were incorporated into the three soils at 2% and 4% levels on dry mass basis. For each soil-organic matter mixtures, the consistency limits significantly increased with increase in the levels of the organic materials. The shear strength significantly decreased with increase in organic matter content. Soils incorporated with groundnut haulms had the least strength followed by cow dung and chicken dung. For all the treatments, water retention decreased with increases in pressure. For sandy loam and clay loam soils, and all organic matter types, water retention increased with increases in organic matter level while that of clay soil decreased with increase in organic matter level. For all the three soils, chicken dung incorporation gave the highest volumetric moisture content followed by cow dung and groundnut haulms. Saturated hydraulic conductivity increased with increase in organic matter level and decreased with increases in compaction level. Model equations generated for estimating maximum shear strength and the moisture contents at which they occurred gave r 2 -values of 0.72 and 0.73, respectively. Measured values of volumetric moisture content were calibrated with calculated values and this resulted in an r 2 -value of 0.97. This implies that the