Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 3/22/2013
Publication Date: N/A
Technical Abstract: Throughout the years, many studies have evaluated changes in soil organic carbon (SOC) mass on a fixed-depth (FD) basis without considering changes in soil mass caused by changing in bulk density. In two study sites, we investigated the effect of different management practices on SOC changes calculated as a (i) concentration, (ii) on a fixed-depth (FD), (ii) on an equivalent soil mass (ESM), and on a minimum equivalent soil mass (ESM-min). The long-term (39 yr) treatments sampled from the first site were: conventional tillage (CT); moldboard plow (MP); no-tillage (NT); and reduced tillage (RT) with winter wheat (Triticum aestivum L.) summer fallow (WF) system. The short-term (7 yr) treatments sampled from the second site were from NT and chisel plow (CP) with multiple crop rotation and continuous corn. Soil samples were collected from 0- to 30-cm depths in both sites. The changes in soils bulk densities were also evaluated. For the first site and on a fixed depth basis, SOC was 21% greater in NT and RT than CT and MP. However, on ESM basis, SOC was 11% greater with NT, MP, and RT compared with CT. At the second site, the changes in SOC concentration was 19.7% greater after seven years of managements compared with initial. Standardizing the soil masses on an ESM showed an average gain in SOC of 5.8 Mg C ha-1 after seven years compared with initial. Estimating SOC levels on an ESM-min showed that SOC stock was not influenced by tillage practices. In general, the ESM calculation scenario appears to be more effective in evaluating SOC stock compared with other scenarios.