The Impact of Litter Quality in Soil Organic Carbon Stabilization.

The Impact of Litter Quality in Soil Organic Carbon Stabilization Cordova, S.C. 1, Castellano, M. 1, Olk, D.C 2, 1Iowa State University, 2USDA-ARS National Lab. for Agriculture and the Environment, Ames, IA Abstract. Plant litter quality is well known to affect litter decomposition rates. More recently, the relationship between litter quality and decomposition rate has been hypothesized to affect soil organic carbon (SOC) stabilization. As a result, plant litter quality may affect both nutrient availability and long-term SOC stabilization. To determine how litter quality affects C mineralization (litter + SOC) and the transfer of plant litter to stable SOC fractions, we conducted a 184 day laboratory incubation with two low-C subsoils and four plant litters. The soils were B horizons with loam and sandy loam textures. The plant litters included corn, soybean, oat, and alfalfa. The incubation consisted of four 46-day cycles with each cycle receiving new input of plant litter. During each 46- day cycle, CO2 flux was periodically measured to calculate cumulative C mineralization. To calculate SOC stabilization, SOC in the fine mineral fraction (<53 um) was measured prior to and at the end of the incubation. The fine mineral fraction is considered to be chemically stabilized against mineralization. Soil type and plant litter quality affected cumulative C mineralization. Cumulative C mineralization exhibited the following trend: oat > alfalfa > soybean > corn. Our results indicate soil type and plant litter interact to affect C mineralization and the stabilization potential of plant litter C.