Subsoiling and Its Effects on Root Yield and Quality of `Beauregard'

Five studies were conducted from 1997 to 1999 to determine the effects of subsoiling on root quality (i.e., root length and shape) and on yield of `Beauregard' sweetpotato. The statistical design for all five studies was a completely randomized block design with six replications (four in Goldsboro in 1997). All studies were conducted on Norfolk fine sandy loam soils. Two studies were done in 1997, one in Kinston and the other in Goldsboro, N.C.; two studies in 1998, one in Kinston and the other in Goldsboro; and one in 1999 in Kinston, N.C. Common treatments in the studies consisted of no subsoiling, V shank subsoil, 30 cm below row (56 cm from peaked ridge) and V shank subsoil, 46 cm below row (71 cm from peaked ridge). Roots were longer, had more creases, and were more misshapen due to ripping (regardless of subsoiling depth) in the 1997 Kinston test. No differences were detected in root quality due to subsoiling in the other four tests. Marketable and total yields were increased in both tests in 1997 with subsoiling; however, a similar yield increase was not obtained with subsoiling in 1998 and 1999. Jumbo yields were increased in Kinston in 1997 and Goldsboro in 1998 with subsoiling; the better response was obtained with 30-cm-depth subsoiling. Jumbo yields in 1999 were the same regardless of treatment. Canner and cull yields were similar in all tests across treatments. Yields may be increased with subsoiling in certain circumstances (i.e, drought or soils with hard pans), and can result in more off-shape roots and longer roots. It appears from these studies that yields may be increased with subsoiling; however, more off-shape roots may be produced, especially under dry conditions or where fields are not routinely subsoiled.