Agroecosystems / Carbon Sequestration Research Focus |
Nebraska Phase I Progress Report
Executive Summary Land managers have long known the importance of soil organic matter in maintaining the productivity and sustainability of agricultural land. More recently, interest has developed in the potential for using agricultural soils to sequester C and mitigate increasing atmospheric carbon-dioxide by adopting practices that increase standing stocks of carbon in soil organic matter and vegetation. Practices that increase the amount of CO2 taken up by plants (through photosynthesis), which then enter the soil as plant residues, tend to increase soil C stocks. Likewise, management practices that reduce the rate of decay or “turnover” of organic matter in soils will also tend to increase carbon stocks. In 2001, we initiated a state wide assessment (Phase I) of how management decisions involving cropping and tillage systems affect soil organic matter. Our approach utilized a variety of resource data (on climate, soils, landuse and management), long-term field experiment results, and the Century EcoSystem Soil Organic Matter Computer Model (Parton, et al., 1987, 1994; Metherall, et al., 1993). An initial Phase I study of cropland in Nebraska utilized existing information on climate, soils and management factors (e.g., drainage, crops grown, production levels and tillage systems) to estimate current rates of C sequestration in Nebraska and derived a value of 1.7 million metric tonnes per year (MMT). This annual rate of C sequestration can be maintained and increased to 2.3 MMT of C if all cropland is converted to a no tillage management system. Model refinements are continuing to help provide an understanding of inputs due to irrigation in collaboration with the University of Nebraska. From this Phase I study, it was apparent that the individual counties had landuse information, including management histories of cropping rotations, drainage histories, fertilizer rates, and conservation practices that were not available in published databases. It was also ascertained from the Phase 1 study that local land managers wanted additional information about C sequestration, and local natural resource districts were willing to report any C sequestered due to conservation practices to the US Department of Energy (DOE). The Phase II study is on going and involves all 93 counties. This approach of involving every county within a state has been proven effective in Iowa and Indiana. For the project to be successful, it was necessary to devise a means of improving communication with the local land managers and collecting the local data. A survey instrument called the Carbon Sequestration Rural Appraisal (CSRA), has been designed, tested and is presently being implemented in each county. This local data will provided additional inputs into the Century Model that were not available in previously published databases, and refined the output for the individual counties and the soils and crop/tillage systems within each county. |