RESIDUAL EFFECTS OF TILLAGE ON COASTAL PLAIN SOIL STRENGTH1

It has been suggested that different tillage methods create soil physical conditions that persist for various lengths of time in the easily compacted soils of the Southeastern Coastal Plain. To test this hypothesis, plots that had been subsoiled and chiseled were conventionally treated (disk-harrowed) for 1 to 3 yr to observe the residual effect of deeper tillage. In the final season, penetration resistances of all plots were measured at field capacity over a 1.90− x 0.55-m cross-sectional cut of soil perpendicular to the rows. This allowed plotting the isostrength patterns of the soil profile of each treatment. Although some residual subsoil tillage effect could still be identified 2 yr after subsoiling, the increase in soil strength (cone index) to 1.5 to 2.5 MPa even after a single year and the inability to position planters precisely over the previous year's subsoiled rows negated any benefit from the previous year's tillage.