Deep Tillage Effects on Compacted Surface‐Mined Land

Abstract

AbstractFederal law requires that surface‐mined prime farmland be reclaimed and restored to premining productivity for row crops (Surface Mining Control and Reclamation Act, Public Law 95–87). In Illinois, reclamation must include soil horizon replacement (topsoil and subsoil) to a depth of 120 cm. Poor physical condition is the most limiting factor in reclarmation in Illinois. The effects of five deep tillage implements (80–120‐cm tillage depth) and two standard agricultural chisel plows (20–35‐cm tillage depth) were evaluated for 6 yr. The seven tillage treatments were applied to a scraper‐placed minesoil that had a high soil strength (2.5–3.5 MPa) throughout the reconstructed profile. A nearby tract of undisturbed Cisne silt loam (fine, montmorillonitic, mesic Mollic Albaqualf) was used as a prime farmland comparison. Crop yields for both corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] significantly increased with tillage depth. Average soil strength decreased and net water extraction increased with increasing depth of tillage. The 1.2‐m‐deep tillage treatments significantly reduced average 23‐ to 114‐cm soil strength from 2.8 to 0.93 MPa. Significant correlation occurred between 23‐ to 114‐cm average soil strength and 6‐yr mean corn (−0.97** [significant at P = 0.01]) and 4‐yr mean soybean (−0.92**) yields. Deep tillage successfully restored productivity; however, the depth of tillage necessary was influenced by initial levels of soil strength.