Agroecosystems / Carbon Sequestration Research Focus |
Iowa Final Report
Recommendations For Further Work Our assessment approach was heavily model-based, utilizing a wide range of geographic databases and county-level statistics, complemented by new information on land use and management gathered using the CSRA. The existing network of long-term experiments provides a solid basis for understanding the influence of various management practices on soil carbon dynamics and are invaluable in assessing the validity of assessment models. However, the establishment of on-farm monitoring locations, where soil C changes could be directly measured over time, would enhance the present quantification approach. It would provide additional information on changes for soils and practices that are at present underrepresented in the existing field experimental network, plus it would provide information reflecting actual on-farm conditions, rather than those of research experimental plots. The feasibility and success of such a monitoring component has been demonstrated in the Canadian Prairie Provinces project (B. McConkey, pers. comm.) and it should be possible to begin establishing such monitoring plots in conjunction with other on going activities such as soil survey. Key attributes of monitoring sites are that they be precisely georeferenced (e.g. with GPS and buried plot markers) to enable resampling at the precise location and that information on the management practices used on the site are registered. The potential exists for collaborating with farmer and conservation associations to begin developing such a network in Iowa. Information gathered from such a network could be used to further test and refine the model-based assessments. The potential effects of soil erosion on CO2 emissions and C sequestration were not included in our analysis and the influence of erosion on regional soil C balance represents an area requiring further study. Clearly, erosion can have a major effect on carbon stocks at a particular location through the transport and redistribution of soil and its associated organic matter. However the impacts will vary depending on whether the location is an erosional or depositional surface. At present, there is considerable debate as to the net effects of erosion on soil C sequestration at the landscape or regional scale. On the one hand, erosion can break up soil aggregate structures and expose protected organic matter to enhanced decomposition, which would lead to increased CO2 emissions. On the other hand, deposition and burial of soil in lower parts of the landscape (or in lake and reservoir sediments) could result in decreased CO2 emissions on a landscape basis. Both effects may be significant, however, there is very little information available to judge which process is dominant or whether the effects cancel out. For many of the conservation practices dealt with in our analysis (e.g. CRP, grass conversions, no-till) erosion rates are likely to be very low and thus an explicit treatment of erosion may not be critical. However, further research on carbon dynamics at the landscape scale is merited to address this issue. In any case, there is no question that the benefits of conservation practices for reducing soil erosion are extremely important, regardless of the impacts of erosion on soil C sequestration. The focus of the assessment has been on strategies to mitigate CO2 increase, through carbon sequestration. However, the resource and land use/land management data compiled in this study form a solid basis for more comprehensive estimates of greenhouse gas emissions and mitigation potential, including estimating fluxes of N2 O and CH4 fluxes associated with cropping practices and CO2 emissions associated with agricultural inputs, such as fuel use and fertilizer manufacture. Both standard accounting approaches such as the IPCC inventory methodology and dynamic models of N2O and CH4 emissions can be applied using the resource data and other information collected in the CSRA. Significant options exist for agricultural mitigation of non-CO2 greenhouse gases and assessment of these potentials would be greatly facilitated by the data and information that have been compiled in the present project. |