Wednesday, November 15, 2006

Iowa Carbon Index Development and Potential Use to Evaluate Soil Carbon Stocks.

Mahdi Al-Kaisi and Thomas Fenton. Iowa State University, 2104 Agronomy Hall, Ames, IA 50011-1010

Soil organic carbon (SOC) content plays a crucial role in sustaining environmental quality and crop production by improving soil physical, chemical and biological properties such as soil water retention, nutrient cycling, erosion control, gas flux and plant root growth. The Iowa Carbon Index (ICI) was developed to evaluate SOC and potential changes due to management of different soil associations within the state. The ICI is affected by variables such as climate, time, parent material, topography and organisms including humans. The importance of SOC to environmental quality and crop production makes the ICI a useful tool for evaluating soil carbon stocks. The objectives of this project were to 1) determine SOC of major soil map units in Iowa for the top one meter and 2) develop an ICI that can be utilized in characterizing different soil map units based on soil carbon stocks. The ICI was developed based on three major components; SOC concentration, soil bulk density and horizon thickness. The ICI was developed only for mineral soils within Iowa that have been cultivated for the past 20 years or more. The study included approximately 410 soil series and 2,300 soil map units across the state. Initial findings show that ICI values reflect the influence of soil forming factors, landforms and human activity on soil carbon stocks. Also, it was found that ICI can explain 70% of soil productivity across the state based on the corn suitability ratings in Iowa.