Soil Physical Properties and Bromide Movement in Relation to Tillage System

Abstract

Conventional (CT) and no‐tillage (NT) effects on soil physical properties and bromide (Br) movement were studied at two locations in North Carolina. The soils were a Norfolk sandy loam (fine‐loamy, siliceous, thermic Typic Paleudult) at a North American eastern Coastal Plain location and a Pacolet sandy clay loam (clayey, kaolinitic, thermic Typic Kanhapludult) at a Piedmont location. Bulk density (Db), macroporosity (Mp), and saturated hydraulic conductivity (Ks) were measured in the plant row (R) and trafficked (T) or untrafficked (N) interrow positions. Simulated rain was applied at two intensities to 1−m² plots after KBr was surface applied. The first simulated rain (30 min) consisted of a low (1.27 cm h⁻¹) or a high (5.08 cm h⁻¹) intensity applied 24 h after Br application. One week later, the high rainfall rate was repeated on all plots. Soil samples for Br determinations were taken 2 days after each rain simulation event to a depth of 40 cm and at the end of the growing season to 120 cm. Soil physical properties were affected by both tillage and position. Bulk density was greater for NT than for CT and in the T compared with R and N row positions. Mp was significantly greater in NT than CT at Coastal Plain location, but the results were opposite at the Piedmont location. Saturated hydraulic conductivity was highly variable ranging from 0.36 cm h⁻¹ to 14.4 cm h⁻¹ at the Coastal Plain location and from 0.06 cm h⁻¹ to 7.12 cm h⁻¹ at the Piedmont location. Saturated hydraulic conductivity at T position was about 100% lower than Ks at N and R positions, but the effect of tillage system was not significant on Ks. The surface 10 cm of soil contained the greatest Br concentration for both tillage systems. For the first and second sampling dates, greater Br movement occurred under NT vs. CT. However, no significant differences were observed in Br movement in the end of season sampling. Because of the coarser soil texture, greater Ks and Mp at the Coastal Plain location, Br moved, to a greater depth at this site than at the Piedmont site.

Keywords:

• Bulk density
• hydraulic conductivity
• porosity
• Br movement
• conventional tillage
• no‐tillage