Maximum Bulk Density Achieved During Soil Compaction as Affected by the Incorporation of Three Organic Materials
Maximum dry bulk density (MDBD) and the corresponding critical moisture content (CMC) were measured in the laboratory for two Trinidadian soils (sandy loam and clay) mixed with three organic materials [peat, farm yard manure (FYM), and filter press mud (FPM)] each at four levels (0, 4, 8, 12% by mass) and compacted using 5, 15, and 25 standard Proctor hammer blows. The compaction tests on the soils were carried out at different moisture contents determined according to the consistency limits of the soils. While the mean MDBD declined significantly (P < 0.001) from 1.51 to 1.26 Mg m–3, the mean CMC increased from 23.2 to 32.9% as added organic materials increased from 0 to 12%. While the former increased, the CMC decreased with increasing compaction efforts. The effectiveness of the organic materials in terms of reducing MDBD and increasing CMC was in decreasing order: peat, FYM, and FPM. Clay soil achieved lower values of MDBD at higher corresponding CMC than the sandy loam. The significant interaction effects observed between some of the experimental factors were used to describe the effect of incorporation of organic materials on soil compaction. Prediction equations for MDBD and CMC were derived for each of the organic materials and all of them combined.