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Soil Organic Carbon Sequestration Rates by Tillage and Crop Rotation

A Global Data Analysis

Environmental Sciences Division, Oak Ridge National Lab., P.O. Box 2008, Oak Ridge, TN 37831-6335

View larger version (33K): [in a new window]   Fig. 1. Comparison between changes in soil organic C (SOC) based on measured soil bulk densities and soil bulk densities estimated using equations from Adams (1973) and Chen et al. (1998). Dashed line indicates 1:1 relationship.

View larger version (31K): [in a new window]   Fig. 2. Soil organic C (SOC) at different soil depths as a result of changing from conventional tillage to no-till. Dashed line indicates 1:1 relationship.

View larger version (20K): [in a new window]   Fig. 3. Comparison of soil organic C (SOC) between conventional tillage and no-till. This analysis includes all tillage experiments except those involving wheat-fallow rotation systems (see text for explanation). Dashed line indicates 1:1 relationship.

View larger version (21K): [in a new window]   Fig. 4. Comparison of soil organic C (SOC) between initial and enhanced rotation cropping systems, which include comparisons between (i) monoculture and continuous rotation, (ii) wheat–fallow and continuous monoculture or rotation cropping, and (iii) rotation with two crops and rotation with three or more crops. This analysis includes all rotation enhancement experiments except those involving a change from continuous corn to corn–soybean rotation (see text for explanation). Dashed line indicates 1:1 relationship.

View larger version (18K): [in a new window]   Fig. 5. The percentage change in annual soil organic C (SOC) sequestration rates under NT, relative to CT. Solid line represents data (solid circles) using a nonlinear regression equation (see Eq. [4] in text). Dashed line represents the 75% quantile of mean values (open squares) using a nonlinear regression equation (see Eq. [5] in text). A data point at Year 8 and 1236% has been excluded from the graph, for easier visual interpretation, but was included in the analysis.

View larger version (19K): [in a new window]   Fig. 6. The percentage change in annual soil organic C (SOC) sequestration rates under enhanced rotation, relative to monoculture or rotation with a lesser number of crops (see text for further explanation). Solid line represents data (solid circles) using a hyperbolic decay regression equation (see Eq. [6] in text). Dashed line represents the 75% quantile of mean values (open squares) using a hyperbolic decay regression equation (see Eq. [7] in text).