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Crop residues may partially dissipate applied loads and reduce soil compaction. We evaluated the effect of corn residue on energy-applied dissipation during wheeling. The experiment consisted of a preliminary laboratory test and a confirmatory field test on a Paleaudalf soil. In the laboratory, an adapted Proctor test was performed with three energy levels, with and without corn residue. Field treatments consisted of three 5.1 Mg tractor wheeling intensities (0, 2, and 6), with and without 12 Mg ha−1 corn residue on the soil surface. Corn residue on the soil surface reduced soil bulk density in the adapted Proctor test. By applying energy of 52.6 kN m m−3, soil dissipated 2.98% of applied energy, whereas with 175.4 kN m m−3 a dissipation of 8.60% was obtained. This result confirms the hypothesis that surface mulch absorbs part of the compaction effort. Residue effects on soil compaction observed in the adapted Proctor test was not replicated under subsoiled soil field conditions, because of differences in applied pressure and soil conditions (structure, moisture and volume confinement). Nevertheless, this negative result does not mean that straw has no effect in the field. Such effects should be measured via stress transmission and compared to soil load-bearing capacity, rather than on bulk deformations. Wheeling by heavy tractor on subsoiled soil increased compaction, independently of surface residue. Two wheelings produced a significantly increase, but six wheelings did not further increase compaction. Reduced traffic intensity on recently tilled soil is necessary to minimize soil compaction, since traffic intensity show a greater effect than surface mulch on soil protection from excessive compaction. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The article presents the study which explores the relationship between suspended sediment concentration (SSC) and turbidity for a small rural catchment in Brazil. It evaluates two calibration methods by comparing the SSC estimates obtained from the calibrated turbidity readings with direct measurements using the soil taxonomy system of the U.S. Department of Agriculture. The first method is derived by relating the turbidity reading to simultaneous measurements of concentration obtained from SSC samples collected from the vicinity of the turbidity probe during flood events, while the second is based on the readings obtained from the turbidity meter when the probe immersed in samples using soils collected from the catchment. The study shows the efficiency of the first method over the second.