Crop Yield and Nitrogen Accumulation Response to Tillage of a Coastal Plain Soil

Delineation of the benefit derived from either surface or subsoil tillage is important for the advancement of soil-conserving crop production systems in the Coastal Plain. The objective of this experiment was to measure the impact of surface and subsoil tillage of a sandy Coastal Plain soil (fine-loamy, siliceous, thermic Typic Kandiudult) on grain yield and nitrogen accumulation for a 2-yr rotation of corn (Zea mays) and wheat–double-cropped soybean {(Triticum aestivum L.) and [Glycine max (L.) Merr.]}. Soils of the experimental plots initially possessed different surface residue and organic matter characteristics because they had received in-row subsoiling with either surface-disking tillage or no surface tillage for the previous 18-consecutive years. The current experiment was conducted from 1997 to 2001, which was an exceptionally dry period. Thus, results of this experiment provide insight into how these cropping and tillage treatments performed during one of the driest 5-yr periods of the last half century. In each year, both phases of the crop rotation were grown in plots with the following tillage treatments: (i) neither surface nor subsoil tillage, (ii) paratill subsoiling without surface tillage, (iii) surface tillage without subsoiling, and (iv) both surface tillage and paratill subsoiling. Soybean was not significantly affected by any tillage treatment. With subsoiling, corn grain yields (4-yr means) were not significantly different with surface-disking tillage versus no surface tillage (4.98 and 4.92 Mg ha⁻¹, respectively). Without subsoiling, corn yields were higher with no surface tillage (4.24 Mg ha⁻¹) than with surface-disking tillage (3.51 Mg ha⁻¹). Likewise, with subsoiling, wheat grain yields (5-yr means) were not significantly different with surface-disking tillage versus no surface tillage (3.12 and 3.24 Mg ha⁻¹, respectively). Without subsoiling, wheat grain yields were higher with no surface tillage (2.80 Mg ha⁻¹) than with surface-disking tillage (2.59 Mg ha⁻¹). Nitrogen accumulations in both shoot dry matter and grain generally followed the treatment responses of grain yield. Thus, during this dry period, surface no-till and the associated accumulation of organic matter could only somewhat compensate for the need to subsoil. With or without surface tillage, paratill subsoiling was very beneficial for corn and wheat yields.