PHYSICAL-PROPERTIES OF A CLAYEY COASTAL-PLAIN SOIL AS AFFECTED BY TILLAGE

A 4-year study was conducted to determine the effects of different til lage systems on physical properties of a clayey Coastal Plain soil. Th e systems no-till NT), fall moldboard plow-spring disk barrow (MB), an d fall chisel plow-spring disk barrow (CP) were used in a winter wheat (Triticum aestivium L.), summer grain sorghum (Sorghum bicolor L. Moe nch) rotation on a Greenville sandy clay loam. Bulk density, saturated hydraulic conductivity, and soil moisture retention were determined o n soil samples collected from the no traffic interrow areas of plots u sed concurrently for a rainfall simulator study of surface runoff and N movement. Examination of changes in the physical properties of the t op soil zone (2.5-10.1 cm) showed that, after 1-1/2 years of tillage t reatment and thereafter, the NT soil was different from the other two treatments. The NT top soil zone had significantly greater bulk densit y, lower saturated hydraulic conductivity, and held more water than th e same soil zone on the other two treatments. Without tillage, the top soil zone of the interrow areas of this sandy clay loam soil bence wa s denser, harder, and bad more smaller sized pores than the same zone on the other two treatments. A final sampling using soil pits showed t he NT treatment to be denser and have lower saturated hydraulic conduc tivity in the 15-38 cm depth zone. The NT had greater soil moisture re tention than the other two treatments at depths greater than 30 cm. Ra infall simulator work on these same treatments showed greater infiltra tion into and less surface runoff from the NT treatment than for the o ther treatments. With greater water-bolding capacity, less surface run off and more water infiltrating during rainfall events, and reduced ev apotranspiration from under the mulch layer, as indicated by observed greater soil surface moisture contents, the NT treatment on this soil was beneficial to soil erosion protection and promoted increased crop production.