Effectiveness of sugarcane residue incorporation at different water contents and the Proctor compaction loads in reducing soil compactibility

Incorporation of crop residues into the soil can reduce its susceptibility to compaction. However, the signi®cance of incorporated crop residue at different soil water contents at the time of compaction and the compaction loads is not well documented. The compactibility of three soils which contained different amounts of sugarcane residue was investigated at different water contents and compaction loads. The compaction loads were chosen to simulate the energy exerted by harvesters, trucks, vanguards, transporters and the standard Proctor test, respectively. A clay loam soil (Typic Ustochrepts), a clay soil (Typic Calciorthis), and a silty clay soil (Typic Torri ̄uvens) were thoroughly mixed with sugarcane residues of 0, 6.9 and 15.3 g per kg of soils, corresponding to 0, 27 and 60 Mg haÿ1, respectively. The sugarcane residue±soil mixtures were compacted using the standard Proctor procedure with different rammer drops, and dry bulk density was measured. The compaction was carried out at different soil water contents related to the consistency limits of the soils. Sugarcane residue was effective in reducing bulk density obtained with different compaction loads at different water contents. The optimum water content for maximum bulk density under compaction load of 551 J was obtained at 0.8 plastic limit (PL). For other compaction loads, however, the optimum moisture content was at PL. Results suggested that soil compatibility caused by heavy machinery of sugarcane production at water content lower than PL, can be reduced by incorporating 60 Mg haÿ1 of sugarcane residue. Filed tests are required in order to verify the laboratory experimental data. # 2000 Elsevier Science B.V. All rights reserved.