Soil and plant response to three subsoiling implements

Many Southeastern Coastal Plain soils require deep (>0.45 m) inrow tillage or subsoiling to disrupt dense tillage/traffic pans and/ or eluvial (E) horizons. Three subsoiling implements [Super Seeder (SS), ParaTill (PT), and Kelly (KE)] were compared on Norfolk (Typic Paleudult) loamy sand to assess their effectiveness in developing and maintaining a proper rooting environment for corn (Zen mays L.). Soil strength (cone index) for the implements was evaluated with and without conventional surface tillage (disking). All three subsoiling implements effectively disrupted the E horizon regardless of surface tillage, but the 67% stand establishment in nondisked treatments was significantly lower than for disked treatments (92%). However, yields were not significantly different. Significant differences in soil strength were measured among subsoiling implements at the beginning of each growing season. In 1985 mean profile soil strength was lower (P 0.10) for SS and PT than for KE. In 1986, soil strength was lower (P 0.10) for SS than either PT or KE. The consistent difference between SS and KE occurred because SS disrupted a larger area than the thinner-shanked KE. Nondisked treatments had mean soil strength that was 0.32 MPa lower within the row than disked treatments, but disked treatments had mean soil strength that was 0.37 MPa lower between the rows. Soil strength results suggest that Coastal Plain soils, which have been subsoiled, are less likely to restrict root development regardless of implement with, or without, prior surface tillage