Journal article
Carbon dynamics determined by natural C-13 abundance in microcosm experiments with soils from long-term maize and rye monocultures

Publication Details
Ludwig, B.
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Soil Biology and Biochemistry
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Understanding carbon dynamics in soil is the key to managing soil organic matter. Our objective was to quantify the carbon dynamics in microcosm experiments with soils from long-term rye and maize monocultures using natural C-13 abundance. Microcosms with undisturbed soil columns from the surface soil (0-25 cm) and subsoil (25-50 cm) of plots cultivated with rye (C-3-plant) since 1878 and maize (C-4-plant) since 1961 with and without NPK fertilization from the long-term experiment 'Ewiger Roggen' in Halle, Germany, were incubated for 230 days at 8 degreesC and irrigated with 2 mm 10(-2) M CaCl2 per day. Younger, C-4-derived and older, C-3-derived percentages of soil organic carbon (SOC), dissolved organic carbon (DOC), microbial biomass (C-mic) and CO2 from heterothropic respiration were determined by natural C-13 abundance. The percentage of maize-derived carbon was highest in CO2 (42-79%), followed by C-mic (23-46%), DOC (5-30%) and SOC (5-14%) in the surface soils and subsoils of the maize plots. The percentage of maize-derived C was higher for the NPK plot than for the unfertilized plot and higher for the surface soils than for the subsoils. Specific production rates of DOC, CO2-C and C-mic from the maize-derived SOC were 0.06-0.08% for DOC, 1.6-2.6% for CO2-C and 1.9-2.7% for Cmic, respectively, and specific production rates from rye-derived SOC of the continuous maize plot were 0.03-0.05% for DOC, 0.1-0.2% for CO2-C and 0.3-0.5% for C-mic. NPK fertilization did not affect the specific production rates. Strong correlations were found between C-4-derived C-mic and C-4-derived SOC, DOC and CO2-C (r greater than or equal to 0.90), whereas the relationship between C-3-derived C-mic and C-3-derived SOC, DOC and CO2-C was not as pronounced (r less than or equal to 0.67). The results stress the different importance of former (older than 40 years) and recent (younger than 40 years) litter C inputs for the formation of different C pools in the soil. (C) 2003 Elsevier Ltd. All rights reserved.


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