Soil Strength Properties Under Four Tillage Systems at Three Long-Term Study Sites in Indiana
There is increasing concern that long-term continuous conservation tillage may cause increased surface soil strength and compaction detrimental to root growth and crop yield. The objective of this study was to characterize distribution of cone index (CI) and vane shear strength (VS) values at three row positions: in row (R), non-wheeltrack interrow (NW), and wheeltrack interrow (WT), under four tillage systems: conventional moldboard plow (PL), chisel plow (CH), ridge-till-plant (RT), and no-till (NT), on three long-term tillage studies on silty soils in Indiana. The Mollisol and Alfisols studied had been under the continuous tillage treatments for 13, 8, and 4 yr, respectively. Maximum cone index (CImax) averaged over three row positions was in the order RT > CH, NT > PL. As less tillage was performed, the zone of maximum strength was closer to the soil surface. Depth of CImax was in the order PL > CH > NT, RT. On the two Alfisols, soil strength in the non-trafficked positions (NW and R) tended to be lower in no-till than in the other tillage treatments, especially in the lower portion (below 15 cm) of the formerly tilled zone. High-strength layers were recorded at 23 to 40 cm and 15 to 22 cm on the PL and CH treatments, respectively. Wheeltrack compaction was more severe under RT and NT than on PL and CH. Vane shear data generally verified the tillage and row position effects found with the cone penetrometer.
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