Enhancement of subsoiling effect on soil strength by conservation tillage

The effects of deep tillage are believed to differ for conventional vs. conservation tillage in the sandy Ultisols of the southeastern Coastal Plains of the United States. To test this, cone indices were measured for a conventional tillage and a conservation tillage treatment before and after in-row subsoil-planting. In the first year of the study, the conservation tillage treatment had a significantly higher moisture content (15.1 vs 12.1% on a dry weight basis) and a mean soil strength that was 0.70 MPa less than the conventional treatment. In the second year, the conservation tillage treatment had a lower moisture content (13.2 vs. 14.9%) and a mean soil strength that was 0.29 MPa greater than the conventional treatment. However, after conventional treatment strengths were corrected for soil moisture content differences, the mean strengths were about the same. The differences in the distribution of the strengths favored the conservation tillage treatment which was evenly distributed while the conventional tillage treatment had areas of higher strength that could more easily inhibit root growth