RESIDUAL EFFECTS OF DEEP TILLAGE VS NO-TILL ON CORN ROOT-GROWTH AND GRAIN-YIELD

Tillage pans occur in many coarse-textured soils and must be ripped by a form of deep tillage to maximize yields. This study compared the lo ngevity of slits produced by subsoiling and slit-till (both to 16 in.) to a no-till treatment, and related slit longevity to corn (Zea mays L.) grain yield and root development. The soil was a Typic Kandiudult with a tillage pan. Both deep tillage treatments were last performed i n 1989; this study was conducted from 1990 through 1992. Roots were ex amined at tasselling each year, and in 1992 thin sections were examine d to determine the effects of the tillage slits on root penetration. C orn grain yields were not significantly different among the three till age treatments in any of the 3 yr. Concentrations of roots in soil pro files did not differ significantly among treatments and roots extended to depths > 40 in. Root observations indicated that the tillage slits affected root development 2 yr after tillage was performed. Residual effects of both subsoiling and slit-tillage on root growth could be se en for up to 2 yr after tillage was imposed, but the effects were gone by the third year. The residual effects of tillage did not affect yie ld in any year.