Organic amendments affect delta C-13 signature of soil respiration and soil organic C accumulation in a long-term field experiment in Sweden

• The contribution of young and old soil organic carbon (SOC) pools to soil CO2 fluxes and specific respiration rates of these fluxes was determined by using C-13 signatures in the Ultuna long-term continuous soil organic matter experiment (C-SOME). Initiated in 1956, the experiment had a range of treatments amended organically and with mineral nitrogen fertilizer under C-3 cultivation until 1999, and thereafter under C-4 (maize) cultivation. In 2011, soil respiration was measured in situ prior to planting, during growth and after harvest. The contributions from C-4- and C-3-C as well as their specific respiration rates were estimated from C-13 differences in SOC and CO2 fluxes. The contributions from C-4-C sources were further separated into autotrophic and heterotrophic respiration by comparing respiration rates before and after harvest. Between 165 and 385g C-4-Cm-2 accumulated during 10years of maize growth, contributing between 4.9 and 8.1% to the total SOC stock. Although recent C-4-C had an average specific respiration rate that was 8.4-22.6 times greater than C-3-C, total soil respiration was generally equally split between C-3-C and C-4-C. Both pools are therefore important sources of CO2 in the overall C budget, and a crucial factor in accounting for SOC stock change caused by management. Experimental treatments influenced specific respiration rates of C-4 plant material and accumulation of SOC stock, demonstrating how greater SOC accumulation can be favoured by high-quality C inputs.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Environmental Sciences (hsv//eng)

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Markvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Soil Science (hsv//eng)

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Jordbruksvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Agricultural Science (hsv//eng)

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