MAXIMUM BULK-DENSITY ACHIEVED DURING SOIL COMPACTION AS AFFECTED BY THE INCORPORATION OF 3 ORGANIC MATERIALS

Maximum dry bulk density (MDBD) and the corresponding critical moistur e content (CMC) were measured in the laboratory for two Trinidadian so ils (sandy loam and clay) mixed with three organic materials [peat, fa rm 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 Proc tor hammer blows. The compaction tests on the soils were carried out a t 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 fo rmer increased, the CMC decreased with increasing compaction efforts. The effectiveness of the organic materials in terms of reducing MDBD a nd increasing CMC was in decreasing order: peat, FYM, and FPM. Clay so il 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 incorp oration of organic materials on soil compaction. Prediction equations for MDBD and CMC were derived for each of the organic materials and al l of them combined.