Agroecosystems / Carbon Sequestration Research Focus |
Iowa Final Report
Phase I: Results Conservation practices were initially estimated as sequestrating 2.3 MMT of C in 1996 (Table 3). Estimates of areas for the conservation practices were provided from databases described above and NRCS personnel. Crops being grown using conventional tillage (includes all acres under reduced tillage systems) accounted for 81% of the area, but these lands were only providing 31% of the C being sequestered. Cropland using no tillage accounted for 8% of the area and provided 17% of the C being sequestered. The amount of land that has been converted to CRP was similar to the no tillage area, but CRP lands were providing 37% of the sequestered C. Soil C changes associated with wetland restoration or cultivation of organic soils were not simulated by Century; instead, mean rates of C change (on a per hectare basis) for cropland conversion to wetland and cultivation of organic soils were taken from Armentano and Menges (1986). Cropland converted to wetland accounted for 0.2% of the area evaluated and sequesters 13,000 tonnes C yr-1 (14,330 tons C yr-1). Organic soils that support crops account for 0.2% of the land evaluated, but these soils are responsible for 170,000 tonnes C yr-1 (187,393 tons C yr-1) given back to the atmosphere. More research is needed on these soils to determine the affect of different management practices. Table 3: Phase I: Summary of C sequestration rates
The existing databases on land-use history, drainage, fertilizer amendments, crop rotations and tillage systems provided a good basis for the Phase I study, but they were limited in their ability to characterize local conditions. Thus a Phase II study was designed to help in bringing C sequestration information to the local land manager. The Phase II study utilized the information gained from the Phase I study, and expanded the scope and complexity of the analysis to include the local land managers’ decision-making and expert knowledge to assist in providing inputs into the Century model. This additional information was gathered for each county in the state, using a new survey instrument -- the Carbon Sequestration Rural Appraisal (CSRA) -- (Brenner et al. 2001). |
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