Tilling compacted forest soils following ground-based logging in Oregon

Graduation date: 1982Implements for tilling compacted forest soils were\ud tested on sites logged with ground-based machines in\ud Oregon. The sites covered a variety of soil conditions\ud ranging from a clay loam to a rock7 2C2 iplemeflts\ud tested included disk harrows (four aies), brusa blades\ud (three sites), standard subsoiler tines (two sites), wing.-\ud ed subsoiler tines (two sites), and rock ripper tines\ud (five sites).\ud Soil density and strength measurements made prior\ud to the tillage operatIons indicated that the depth of\ud compacted soil within primary skid trails exceeded 12 inches\ud and was often detectable to a depth of 18 inches.\ud Logging debris typically was incorporated into the skid\ud trail surfaces.\ud The disk harrow proved ineffective for loosening compacted\ud forest soils at depth when: 1) the soil had a high\ud rock content, 2) disk weighting was insufficient, or\ud 3) the trail cross-section was concave and the harrow\ud wide.\ud The brush blade failed to loosen the deeper layers of\ud compaction and resulted in transfer of some of the loosened\ud soil to the trail edges. The short closely-spaced\ud tines did not allow loosened soil and logging debris to\ud pass between the tines.\ud The performance of subsoiler and rock ripper tines\ud was favorable in the rocky coarse-grained soils and some\ud of the cohesive soils. However, plastic flow rather than\ud shatterin.g occurred when tines operated below their crit-..\ud ical depth. The critical depth was controlled by soil\ud conditions and tue geometry. The winged subsoiler tines\ud resulted in 30 to 64 percent greater shattering than did\ud standard subsoiler tines at a ripping depth of 1.5 feet.\ud Close tine spacing caused logging debris to accumulate in\ud front of the tines. The tines produced large angular clods\ud when working in a cohesive soil. These clods did not\ud break down after heavy rains. Clods from coarse-grain\ud soils broke down readily when moistened.\ud A trapezoid-shaped representatjoii of the soil sbattering\ud pattern produced by tines was shown to compare adequately\ud with actual shattering patterns. A computer program\ud was developed to analyze ripping depth and tine\ud spacing combinations resulting in maximum shattering\ud across the skid trail width.\ud The cost of the tillage operations ranged from $89\ud to $228 per mile of skid trail (1980-1981 dollars)