Background and Aims Previous studies have clearly
shown substantial increases of soil organic carbon
(SOC) in agricultural soils of Yellow River reaches.
Those soils did not receive organic fertilizer input, but
did receive chemical fertilizer inputs. Thus, to
investigate the hypothesis that the observed SOC
increases were driven by chemical fertilizer additions,
a maize pot experiment was conducted using a
Fluvisol that developed under C3 vegetation in the
Yellow River reaches.
Methods Using the natural 13C abundance method we
calculated the SOC renewal ratio (Crenewal), and
separated total soil organic carbon (TOC) into maizederived
soil organic carbon (SOCmaize) and original soil
organic carbon (SOCoriginal). Carbon dioxide fluxes
and microbial biomass carbon (MBC) were determined
by closed chamber method and fumigationextraction
method, respectively. The experiment
included five treatments: (1) NPK: application of