Soil compaction process studies have more recently involved some soil tests frequently used in soil mechanics. Seeking a better understanding of the application of the Proctor normal test for agricultural purposes, this study aimed to evaluate the soil compaction curve, obtained through this test, and the effect of the degree of compaction on the soil moisture characteristic curves. For the development of this study, a Dusky Red-Latosol (LR), a Red Yellow-Latosol (LV) and a Dark Red-Latosol (LE) submitted to annual crop, pasture and natural forest were used. The optimum moisture content average for LR (0.31 kg kg-1) was greater than that for LV (0.22 kg kg-1) and LE (0.25 kg kg-1) for all soil management systems. For the LV and LE, the maximum dry bulk density increased in the following order: annual crop, pasture and natural forest (for LV, 1.92; 1.94; e 1.95 kg dm-3, respectively and for LE 1.89; 1.91; e 1.96 kg dm-3 respectively); while for the LR the order was forest, annual crop, pasture (1.83; 1.92 and 1.93 kg dm-3, respectively). The soil moisture characteristic curves were shifted due to the variation of the degree of compaction. The soil moisture characteristic curves obtained for the degree of compaction in the humid branch and the dry branch of the compaction curve tended to move to the right and to the left, respectively, in relation to the soil moisture characteristic curve for the degree of compaction of 100%. For suctions smaller than 10 kPa, 93% of the soil moisture characteristic curves were located to the right of the soil moisture characteristic curve for the degree of 100% compaction. Both in the dry and humid branches, as the degree of compaction increased, the available water content tended to decrease in the three soil types and for all the soil management conditions.
Proctor normal; soil moisture characteristic curve; Latosols