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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOP KNOWLEDGE BASE AND QUANTITATIVE TOOLS FOR OPTIMAL CROPS AND MGMT PRACTICES FOR VARIABLE LTD WATER CONDITIONS IN THE GREAT PLAINS

Location: Agricultural Systems Research Unit

Title: A rapid and cost effective method for soil carbon mineralization under static incubations

Authors
item Sherrod, Lucretia
item Reeder, Jean -
item Hunter, William
item Ahuja, Lajpat

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: August 15, 2009
Publication Date: November 1, 2009
Citation: Sherrod, L.A., Reeder, J.D., Hunter, W.J., Ahuja, L.R. 2009. A rapid and cost effective method for soil carbon mineralization under static incubations. ASA-CSSA-SSSA Annual Meeting Abstracts.

Technical Abstract: Soil incubations with subsequent determination of carbon dioxide (CO2) are common soil assays used to estimate C mineralization rates and active organic C pools. Two common methods used to detect CO2 in laboratory incubations are gas chromatography (GC) and alkali absorption followed by titration (NaOH). These methods have various strengths and weaknesses that are realized in cost of equipment and analysis time. A new approach makes use of an infrared gas analyzer (IRGA) with a simple single path analysis. This is significantly less costly than a dual channel system. The objectives of this study were (i) evaluate if the IRGA, GC and NaOH methods for CO2 determination obtain the same concentrations over 4 time periods (1, 3, 10 and 21 day); (ii) how well do these methods correlate to each other across incubation times; (iii) estimate the limit of quantitation (LOQ); and (iv) estimate the concentration of CO2 and O2 gases in the chamber headspace that shows respiration suppression. Soil samples were collected from along a catena sequence from 4 cropping systems within 2 field replications (n=24) to obtain a range of labile organic matter. The IRGA method had similar results as GC and NaOH methods with no significant differences by day 21 of the incubation. The GC had the lowest LOQ of 90 followed by 115 and 600 ppm CO2 for IRGA and NaOH methods respectively. Correlations of GC vs. NaOH, GC vs. IRGA, and NaOH vs. IRGA over the 21 days had R2 values of 0.93, 0.94, and 0.92 respectively. The headspace CO2 and O2 that showed respiratory suppression was 9.1% and 10.9 % respectively. The single cell IRGA system is a rapid and economic estimation of C mineralization and active soil organic C pools.

Last Modified: 7/24/2014
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