Monday, November 13, 2006

Tillage System Impacts on Soil Carbon Stocks in Northcentral Illinois.

C.A. Sabdo and M.E. Konen. Northern Illinois Univ, Dept of Geography, 118 Davis Hall, DeKalb, IL 60115

Illinois no-till management systems are currently being credited a rate of 0.34 Mg C/ha/yr through the Illinois Conservation and Climate Initiative’s carbon credit program.  This is a fixed value for all of Illinois regardless of differences in management levels and soil properties.  At present there are 626 different soil series mapped in Illinois with a wide range of properties and carbon sequestration potential.  Three spatially significant northern Illinois soils were examined in order to quantify the impact of 16 years of continuous no-till on soil organic carbon (SOC) stocks.  The soils were the Catlin (Oxyaquic Argiudoll), Drummer (Typic Endoaquoll), and Elpaso (Typic Endoaquoll) series.  We quantified SOC stocks in adjacent no-till and conventional or reduced-till fields.  SOC stocks were determined in 10 cm increments down to 50 cm.  Maximum A horizon thickness in these soils extended to 49 cm.  We will discuss how the depth of quantification (10, 20, 30, 40, or 50cm) determined whether a no-till soil had less, more, or the same SOC content as its paired neighbor.  No significant difference was observed in SOC stocks for the 0-50 cm depth for the Drummer soil under conventional and no-till management.  The Catlin and Elpaso soils did exhibit carbon sequestration under no-till but the amount and rate is highly dependant on the reporting interval.  Carbon sequestration rates over the 16 year period for the 0-50 cm depth interval were calculated to be 2.7 Mg/ha/yr in the Elpaso soil and 2.0 Mg/ha/yr in the Catlin soil.  Utilizing a single carbon credit rate for Illinois no-till systems with different soils within and among fields is not realistic.  Significant advances in field and laboratory quantification of SOC stocks needs to be implemented for specific soils and management systems as carbon trading expands in the future.