Amos, Brigid (Univ. of Nebraska – Lincoln, 236 Kiem Hall, Dept. of Agronomy and Horticulture, Lincoln, NE, 68583-0915; Phone: 402-472-7989; Email: bamos2@unlnotes.unl.edu)

Approaches to Separating Autotrophic and Heterotrophic Contributions to Soil Respiration in Maize-Based Agroecosystems

B. Amos*, D.T. Walters, S. Madhavan, T.J. Arkebauer, D.L. Scoby

We will present two approaches to separating soil respiration into two specific sources: an autotrophic source (R_a), defined as combined root respiration and the respiration of soil microorganisms residing in the rhizosphere and deriving energy from root exudation and turnover, and a heterotrophic source (R_h), defined as the respiration of soil microorganisms and macroorganisms not directly under the influence of the live root system and deriving energy from soil organic matter. The two approaches discussed are the root exclusion technique (i.e., measuring soil respiration with and without roots) and a method in which delta ¹³C measurements are made of soil respiration samples collected from root-excluded and non root-excluded soil. These methods were used to separate R_a and R_h in irrigated and rainfed maize-based agroecosystems in the western USA Corn Belt. We will present preliminary results and consider the advantages and potential pitfalls of both methods.