Submitted to: Southern Conservation Tillage for Sustainable Agriculture Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/27/2005
Publication Date: 6/27/2005
Citation: Robinson, S.J., Frederick, J., Novak, J.M., Bauer, P.J., Watts, D.W. 2005. Changes in soil P levels with innovative and traditional cropping systems [abstract]. Proceedings of the Southern Conservation Tillage Systems Conference, June 27-29, 2005, Florence, South Carolina. p. 202.
Technical Abstract: Most agricultural fields on the southeastern Coastal Plain contain a diversity of soil types, resulting in a wide-range of crop productivity and consequently, soil fertility levels across the landscape. Conservation tillage results in the accumulation of P near the soil surface, thereby making it susceptible to offsite movement in runoff water. Thus, low-yielding areas of fields planted with conservation tillage may be a significant source of P in runoff water. However, these areas should also show the greatest benefit from the precision application of P fertilizer. In this study, we monitored site-specific changes in soil fertility levels resulting from the use of conservation-tillage (CT) and traditional-tillage (TT) systems. This study was conducted from 1998 through 2005 using a split-field comparison at the Clemson University Pee Dee Research and Education Center in Florence, SC. A 14-acre field was split in half, with one half of the field receiving traditional production practices (disking, in-row subsoiling, traditional herbicides) and the other a conservation-tillage production system (no surface tillage, broadcast deep tillage, Roundup Ready herbicide program). Phosphorus was precision applied on the CT side of the field based upon soil samples taken on a 50-ft grid basis and applied on the TT side of the field at a rate based upon a bulk soil sample taken across that side of the field. Corn (Zea mays L.) was planted in the study in 1999, 2001, 2003 and cotton (Gossypium hirsutum L.) in 2000, 2002, 2004. Phosphorus was the only nutrient we found that could be precision applied. Initially, there were areas high in soil P (greater than 100 lbs/acre) on both sides of the field. These were either low-yielding areas or areas where water ponded after major rainfall events. On the TT side, those areas remained high in soil P for the duration of the study. Other areas in the TT side became deficient in soil P over time. In contrast, areas of the CT side became more uniform in soil P over time, near the 50 to 60 lb/acre level. Results showed precision application of P can effectively reduce soil P to acceptable levels when conservation tillage practices are used on the southeastern Coastal Plain.