IN-ROW SUBSOILING AND CONTROLLED TRAFFIC EFFECTS ON COASTAL PLAIN SOILS

ABSTRACT. Soil compaction is an acute problem in the southeastern U.S., requiring periodic subsoiling to alleviate densely compacted soils. Controlling vehicle traffic is one method that has been recommended for reducing the negative effects of vehicle traffic. The objective of this study was to determine the differences in soil bulk density and cone index resulting from the interactions of surface tillage, subsoiling, and controlled traffic in a long-term corn-soybean cropping system experiment in a Coastal Plain soil in the southeastern U.S. Traffic or no-traffic treatments were accomplished using an experimental wide-frame tractive vehicle (WFTV), which enabled operations without traffic on 6.1 m wide growing zones. Subsoiling treatments included no subsoiling, annual in-row subsoiling, and initial one-time subsoiling on 25 cm centers to completely disrupt the soil to the 40 cm depth. Surface tillage treatments were no-tillage or disking and field cultivation. Soil measurements were taken after the treatments were imposed for five years. Bulk density and cone index measurements were taken at three positions in the plots: the trafficked row middle, the in-row position, and the non-trafficked row middle. Four significant conclusions from this study can be drawn: (1) vehicle traffic increased soil bulk density nearest the surface in all row positions, with the greatest increases occurring directly in the trafficked row position where equipment traffic was applied; (2) no-tillage caused significantly increased bulk density values near the soil surface in all three row positions; (3)annual in-row subsoiling effectively relieved soil compaction, while the initial complete disruption subsoiling treatment had similar bulk density and cone index values as the no-subsoiling treatment; and (4) in-row subsoiling also loosened th