Plant Soil Environ., 2012, 58(6):249-255 | DOI: 10.17221/532/2011-PSE

Distribution of recently fixed photosynthate in a switchgrass plant-soil system

D.R. Chaudhary^1,2, J. Saxena¹, N. Lorenz¹, R.P. Dick¹

¹ School of Environment and Natural Resources, Ohio State University, Columbus, USA

² Discipline of Wasteland Research, Central Salt and Marine Chemicals Research Institute, Council of Scientific and Industrial Research, Gujarat, India

The use of switchgrass (Panicum virgatum L.) as an energy crop has gained great importance in past two decades due to its high biomass yields on marginal lands with low agricultural inputs and low maintenance requirements. Information on the allocation of photosynthetically fixed C in the switchgrass-soil system is important to understand the C flow and to quantify the sequestration of C in soils. The allocation of ¹³C labeled photosynthates in shoot, root, soil, and in microbial biomass carbon (MBC) of rhizosphere and bulk soil of 45 days old, greenhouse grown-switchgrass was examined during 20 days ¹³C-CO₂ pulse labeling period. The total ¹³C recovered in the plant-soil system varied from 79% after 1 day to 42% after 20 days of labeling. After labeling, 54%, 40%, and 6% excess ¹³C resided in shoot, root and soil, respectively on day 1; 27%, 61% and 11%, respectively on day 5 and 20%, 63% and 17%, respectively day 20 after labeling. The maximum incorporation of ¹³C from roots into the MB of rhizosphere soil occurred within the first 24 h of labeling. The excess ¹³C values of rhizosphere soil and rhizosphere MBC were significantly higher than excess ¹³C values of bulk soil and the bulk soil MBC, respectively. The proportion of excess ¹³C in soil as MBC declined from 92 to 15% in rhizosphere soil and from 79 to 18% in bulk soil, for 1 day and 20 days after labeling, respectively. The present study showed the effectiveness of ¹³C labeling to examine the fate of recently photosynthesized C in soil-plant (switchgrass) system and dynamics of MBC.

Keywords: Panicum virgatum L.; 13C pulse labeling; microbial biomass; rhizodeposition; carbon allocation; C sequestration

Published: June 30, 2012  Show citation