ABSTRACT:Field-scale experiments on degraded soils comparing management systems would facilitate a better understanding of the soil organic carbon (C) landscape dynamics associated with transition to conservation systems. We assessed the effects of soil management practices and terrain attributes on soil organic C in a 9 ha (22.2 ac) Alabama field (Typic and Aquic Paleudults). Treatments were established in strips across the landscape in a corn (Zea mays L.)-cotton (Gossypium hirsutum L.) rotation. Treatments included a conventional system (chisel plowing/disking without cover crops) with or without dairy manure, and a conservation system (no-till and cover crops) with and without manure. A soil survey, topography, soil electrical conductivity, initial soil organic C and soil texture were used to delineate management zones or clusters. After one rotation cycle (30 months), averaged across 240 positions distributed over the entire field, no-till or conventional tillage + manure increased soil organic C (0 to 5 cm; 0 to 2 in depth) by ~50 percent compared to conventional tillage (7.34 and 7.62 vs. 5.02 Mg ha-1; 3.28 and 3.40 vs. 2.24 t ac-1, respectively); but no-till+manure increased soil organic C by 157 percent. Initial soil organic C content was the most common correlated variable with soil organic C changes (?SOC) across the landscape for all treatments and conservation systems had greater soil organic C increases relative to conventional systems at low soil quality landscape positions. Our results show the potential to sequester C using high-residue producing conservation systems and manure is scale dependent, and may be higher than previously expected for degraded soils in the southeastern United States.