Fig. 1.

Areal image showing crop and rangelands in glaciated regions of South Dakota and soil bulk density map derived from the STATSGO database. The Missouri River is the western edge of the regions.

 


Fig. 2.

A flow chart showing the different information layers used to calculate the C sequestration amounts (δSOC/δt) and partial C footprints.

 


Fig. 3.

SOC model validation using data reported by Larson et al. (1972), Barber (1979), and Huggins et al. (1998). Carbon amount in the surface (0–15 cm) soils after long-term studies are compared. The 95% confidence interval is the dashed lines on the chart.

 


Fig. 4.

The relationship between the number of annual soil mixing events (tillage, disking, and cultivations) vs. the first-order SOC mineralization rate constant (kSOC [g (g × yr)−1]. The 95% confidence interval is shown on the chart.

 


Fig. 5.

The influence of year and five sampling regions on the average amount of SOC contained in the surface 15 cm. The number of samples in the NC, C, NE. EC, and SE regions was 20,217, 10,278, 23,891, 34,832, and 14,218, respectively. The 95% confidence interval is shown on the graph.

 


Fig. 6.

Temporal changes in the South Dakota state-wide wheat (Triticum aestivum L.), soybean [Glycine max (L.) Merr.] and corn (Zea mays L.) yield per hectare (NASS, 2011).

 


Fig. 7.

Simulated temporal changes in SOC resulting from conservation and no-tillage adoption and increasing amount of NHC returned to soil. In this chart, the NHC value is multiplied by 10, whereas the sequestered C value is multiplied by 20. The initial conditions for this simulation were kSOC = [0.030 g (g × yr)−1], SOC = 60,000 kg C ha−1; and kNHC = 0.20 g [(g × yr)−1].