Regional Assessment of Soil Compaction and Structural Properties under No-tillage Farming
2007
Blanco-Canqui, Humberto | Lal, R.
No-tillage (NT) farming is a proven technology for soil and water conservation, but its impacts on soil compaction and structure development are soil- and site-specific. We conducted a regional assessment of long-term (>5-yr) NT farming impacts on soil compaction, structure, and aggregate-associated soil organic carbon (SOC) concentration across 13 contrasting but representative soils in the eastern USA, each within a Major Land Resource Area (MLRA: 111C, 98, 114B, and 122 in Indiana; 111A, 111B, 111B2, 99, 111D, 124, and 126 in Ohio; and 147 and 127 in Pennsylvania). Each MLRA comprised NT, chisel plow (CP), and woodlot (WL) land uses. Impacts of NT management were moderate on soil compaction, small on soil structural properties, and nonsignificant on aggregate-associated SOC concentration. No-tillage soils had higher cone index (CI) and shear strength than CP in nine out of the 13 MLRAs, and they had the highest CI (∼2 MPa) and shear strength (>180 kPa) within MLRAs 122 and 124. Bulk density (ρb) in NT was higher than in CP soils only in 111B (1.31 vs. 1.18 Mg m⁻³) and 127 (1.37 vs. 1.17 Mg m⁻³). No-tillage farming increased the mean weight diameter (MWD) of aggregates by a factor of 1.6 in MLRA 99, by 3.0 in 124, and by 5.3 in 111A, and reduced their tensile strength (TS) in 114B, 126, and 111B by a factor of ∼2.5. Macroaggregates (>1 mm) contained 15 to 100% more SOC than microaggregates. Woodlot soils had the lowest ρb and TS and the highest MWD and aggregate-associated SOC concentration. The MWD increased with increasing SOC concentration. Overall, the impacts of no-tillage farming on soil compaction and structure were small compared with plow tillage.
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