Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2004
Publication Date: 12/20/2004
Citation: Raper, R.L., Sharma, A.K. 2004. Soil moisture effects on energy requirements and soil disruption of subsoiling a coastal plain soil. Transactions of the ASAE. 47(6):1899-1905. Interpretive Summary: Breaking up compacted soil layers using tillage is necessary for many U.S. soils. However, the energy costs can be substantial. Also, tillage could result in excessive surface soil disruption that could unnecessarily expose bare soil to rainfall. This experiment was conducted to determine the energy requirements and the soil disturbance caused by two subsoilers, a straight shank and a "minimum-tillage" shank at four moisture contents in a Coastal Plains soil. The results show that increased energy requirements and increased soil disturbance results from subsoiling at extremely dry conditions. A "minimum-tillage" shank required more energy than the straight shank but also caused more soil disturbance on the soil surface. Producers wishing to subsoil to disrupt compacted soil layers should not operate at either extreme of soil moisture. Subsoiling in extremely wet soil conditions may lead to additional compaction due to vehicle traffic. Subsoiling in extremely dry soil conditions may increase energy requirements and surface disruption.
Technical Abstract: An experiment was conducted to determine the optimum moisture content to subsoil based on tillage forces and soil disruption. Two different shanks, a straight shank and a "minimum- tillage" shank, were tested in a Coastal Plain soil in the soil bins of the National Soil Dynamics Laboratory in Auburn, AL. A three-dimensional dynamometer was used to measure tillage forces and a laser profilometer was used to measure soil disruption. Tillage forces and soil disruption measured from the driest moisture content were greater than all other moisture contents tested. The "minimum-tillage" shank required more energy and disrupted less soil than the straight shank. Two indices, the spoil resistance index (SRI) and the trench specific resistance (TSR), were created, respectively, to assist in determining the minimum amount of draft force necessary for minimally disturbing the surface soil and for maximally disrupting the deeper soil profile. Reductions in SRI were found for operating either of the shanks in the wet soil condition, which resulted in minimum values of draft coupled with minimum surface disruption. Reduced values of TSR were found for the straight shank compared to the minimum-tillage shank, which results in minimum values of draft necessary to maximally disturb the soil profile.