|Gonzalez, Javier - IOWA STATE UNIVERSITY|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 4, 1999
Publication Date: N/A
Technical Abstract: An understanding of C dynamics in soils is necessary to develop management options to enhance C sequestration. The objective of this study was to relate the clay mineralogy of a silt loam soil to the dynamics of C sequestration. Oats grown in the soil were pulsed labeled with **14CO2. After senescence, the surface residue was removed and the labeled roots were incubated for 360 days. The soil clay fraction (<2 um) was separated into coarse, medium and fine clay size-fractions (02-2.0, 0.06-0.2 and <0.06 um, respectively) by centrifugation. X-ray diffraction indicated that quartz, illite and kaolinite are the dominant mineral phases in the coarse clay fraction while smectite is the dominant phase in the fine clay fraction. Scintillation analysis indicated that **14C activity increased for all fractions from 0 to 360 days of incubation. The highest specific **14C activity occurred in the fine clay fraction. The results suggest that smectite play a critical role in humification and C sequestration in soils.