The compaction of agricultural soils is a phenomenon of great concern in Soil Science. The major goal of research on the mechanical behavior of soil is to identify the least degrading soil management systems. In general, at a same compaction level, the higher content of organic matter, the lower maximum density and higher critical moisture for compaction, which consequently decreases the risk of physical degradation of the soil. The purpose of this study was to study the compressibility of a dystrophic cohesive yellow latosol of the coastal plains of Alagoas. Three areas were selected in sugarcane plantations of the sugar mill Santa Clotilde, representing three management systems: sugarcane under irrigation (IMS), sugarcane under irrigation and vinasse application (SMV) and sugarcane with vinasse and filter cake application (SMVT). The three management systems were used in the 2003/2004 growing season and the soil sampled in February 2007. These systems were compared with each other and to a control area, represented by native forest (NF). The maximum soil density and critical moisture for compaction were evaluated in the layers 0-0.20, 0.20-0.40 and 0.40-0.60 m. The ability of sugarcane residues to dissipate part of the compacting energy was assessed in Proctor tests at four levels of compression. The energy dissipated by crop residues was assessed in disturbed samples in the 0-0.20 m layer only. In the irrigated management system (IMS), without cane residue application, the maximum density was highest and critical soil moisture for compaction lowest. Of the different management systems, the most efficient in dissipating compression energy was the area under application of vinasse and filter cake, followed by the system of irrigation with vinasse, respectively, with respective values of 54 and 41 % dissipation at the highest level of compression energy. It was also observed that the dissipation of compression energy was higher at higher energy levels.
soil compaction; organic matter; compression energy dissipation; Proctor test; sugarcane residues
