Influence of Corn Residue on Compression and Compaction Behavior of Soils

Crop residues have low densities and are somewhat elastic in nature. The presence of these residues in the soil or at the soil surface might reduce the severity of soil compaction. The objective of this study was to investigate the compression and compaction behavior of soils in the presence of corn residue. Compression behavior of soil-residue mixtures was studied in the laboratory using the uniaxial compression test. Treatments included three size fractions (0.25-0.50, 1.00-2.00, and 3.36-5.66 mm) of corn residue, four amounts of residue addition, three soil water contents, and three soils (Webster clay loam, Sargent silt loam, and Zimmerman sand). Compression samples consisted of 60 g of wet soil mixed with 0.0, 0.5, 1.0, and 2.0 g of corn residue. The compression index of residue mixed Webster clay loam or Sargent silt loam was approximately the same for various amounts and sizes of corn residues. The compression index of Zimmerman sand increased slightly with an increase in the amount of corn residues. However, for a given amount of corn residue, there was no difference in the compression index of Zimmerman sand for various residue fractions. Bulk density at a reference stress (σₖ = 100 kPa) decreased slightly with an increase in the amount of corn residue addition. Assuming that the residues are uniformly mixed in the top 15 cm of soil or concentrated in the wheel track (one fourth of the surface area), calculations showed that corn residues available on the farm (6.7 t/ha assuming 100 bushel/acre corn yield) will have little influence on compression parameters and thus on compaction of soils. Influence of surface residues on field soil compaction was tested in an aboveground soil bin containing a top layer of Waukegan silt loam. Residue treatments included 0.0, 3.4, 6.7, and 10.1 t/ha of corn residues on the soil surface. Measurements included normal stress at 200-mm depth under the center of a wheel track during the passage of a tractor, and soil sinkage and bulk density profile after the passage of a tractor. Differences in the maximum normal stress at 200-mm depth were <80 kPa between bare and residue-covered plots. This reduction in maximum normal stress is equivalent to a reduction in bulk density of 0.12 Mg m⁻³ due to the presence of corn residues. However, because of the soil variability, the bulk density profile showed no significant difference due to the presence of surface residues. In summary, both laboratory and field tests in this study showed minimal beneficial effects of using corn residues in reducing the compression and compaction of soils. This conclusion, however, assumes a maximum amount of 10.1 t/ha chopped corn residue that is approximately equal to a yield of 150 bushel/acre (assuming a grain to straw ratio of 1:1).