Nitrogen-sulfur relationships in corn as affected by landscape attributes and tillage

Corn (Zea mays L.) root access to the B horizon is needed for adequate sulfur nutrition on sandy, highly leachable Coastal Plain soils with tillage pans. Deep tillage increases rooting depth on these soils, but the interaction of deep tillage with landscape attributes in complex toposequences is not well understood. The effect of chisel plowing 35 cm deep, subsoiling 25 cm deep, and disking 12 cm deep on N and S accumulation by corn on a well-drained toposequence of Coastal Plain soil was studied in 1984 and 1985. Nitrogen and S concentrations of above-ground biomass were measured at anthesis (N-a and S-a, respectively) and at harvest (N-a and S-a, respectively). Soil surface curvature (CRV) (i.e., its convexity or concavity), and depth to the B horizon (BDEP) were correlated with S-a in both years. Extreme drought in early 1985 resulted in a stronger negative linear response of S-a with BDEP in the chisel plow and disk treatments compared with the subsoil treatment. The N-a/S-a ratio was negatively correlated with BDEP for all treatments and with CRV for chisel plow and disk tillage. Deep tillage had the greatest positive effect on S accumulation by corn at the linear slope position, which was the landscape position with the greatest depth to the B horizon.