Agroecosystems / Carbon Sequestration Research Focus |
Iowa Final Report
C Sequestration Rates For Conservation Practices The database ‘Iowa Carbon Potentials’ allows land managers to quantify soil C changes for present land management systems and shows what effects various conservation treatments will have on soil C changes. Table 9 provides an example of inputs needed to quantify changes in soil C due to management changes for a corn-soybean crop rotation, and also includes cropland converted to CRP. This example is for a non-hydric, silty clay loam (SICL) soil in Adair County. Table 9: Example query methods for the ‘Iowa Carbon Potentials’ database
Table 10 summarizes the soil C changes (2004 value) due to management options as outlined in Table 9. Soil C increases as tillage disturbances decrease in options 1 and 2. Options 3 and 4 show large increases in soil C when cropland is converted to permanent grass, such as buffers and grass waterways. Both grass options illustrate that by combining legumes and grasses together, the soil C increase is almost double. The CRP example also includes both grass options. If legumes were seeded when the CRP was established, then the 50% legume, 50% grass option should be used. Options 5-7 reflect what happens when CRP lands, which were planted using 100% grasses are returned to crop production. When a crop rotation of corn-soybean using an intensive tillage system is used, soil C decreases by 0.52 tonnes ha-1 yr-1 (0.23 tons ac-1). A moderate tillage system shows little change, while a no tillage system is increasing soil C at a rate of 0.12 tonnes ha-1 yr-1 (0.05 tons ac-1 yr-1). Options 8-10 reflect the result of CRP lands, planted to 50% legumes and 50% grasses, returned to crop production. When a crop rotation of corn-beans using an intensive tillage system is used, soil C decreases by 1.55 tonnes ha-1 yr-1 (0.69 tons ac-1 yr-1). A moderate tillage system shows a decrease of 1.01 tonnes ha-1 yr-1 (0.45 tons ac-1 yr-1), while a no tillage system shows a decrease of soil C of 0.84 tonnes ha-1 yr-1 (0.37 tons ac-1 yr-1). These results demonstrate how management decisions can increase or decrease soil C. Using the database and the approaches outlined in this report, land managers working with local conservation planners will be better equipped to address local conditions for cropping, tillage, soils, and management systems desired by the customer. Table 10: C sequestration rates for the first ten years after a management change
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