Plow Power Requirements for Forestry Site Preparation
Abstract In this field study, data were collected to determine power requirements required by a trailing site preparation plow and the magnitudes of dynamic forces experienced by a plow during normal operation and during impact with stumps or other obstructions. Drawbar pull data were collected from five different tillage treatments on a recently harvested loblolly pine (Pinus taeda) site in central Alabama. The five treatments were: 1) a coulter, ripping shank, and four bedding disks; 2) a coulter, ripping shank, and two bedding disks; 3) a coulter and ripping shank; 4) a coulter alone; and 5) a ripping shank alone. A 330 kN [75 000 lb] capacity tension load cell was used to measure the drawbar load, a GPS receiver recorded tractor speed, four direct current displacement transducers (DCDT’s) monitored the depth of the disks, and two optical tachometers measured the speed of the tractor’s front and rear drive shafts. Each treatment produced significantly different drawbar loads (to alpha levels less than 0.001). The resulting mean loads were 46.0 kN [10 300 lb], 33.5 kN [7530 lb], 31.5 kN [7080 lb], 15.8 kN [3560 lb], and 43.4 kN [9760 lb] for treatments one through five, respectively. Maximum recorded drawbar load during a collision with a stump was 338.9 kN [76 188 lb].
Soil compaction caused by high axle loads— review of concepts and experimental data
Abstract Current concepts, theoretical analysis and experimental data on soil compaction under high axle loads are critically reviewed and analyzed. Based on theoretical considerations and experimental data it is suggested that subsoil compaction is expected to occur under specific conditions (wet, homogeneous, and deep soil under high contact pressures). Measured changes in soil bulk density, physical properties, and crop yields (published in the literature), attributed to high axle load induced soil compaction, are not uniquely proven and can be attributed to other processes as well. Further research directed towards understanding and forecasting changes of soil properties under traffic loads is recommended.
Measurement, interpretation and modelling of soil compaction
. The analysis of some experimental field results is used to illustrate the problem of measuring and evaluating compaction treatment effects below wheel ruts of different depths. A solution to the problem is described which traces vertical soil movement to allow comparisons between treatments to be made using soil elements which derive from the same depth in the undisturbed profile, irrespective of their depths in the compacted profile. 
 
 
 
A soil compaction model, which predicts the changes in dry bulk density resulting from the passage of wheels, is briefly described. Examples are given of its use in comparing the compaction caused by various types and arrangements of wheels and in assessing the contribution made by a particular input variable.