The effect of chemical fertilizer application on carbon input and export in soil—A pot experiment with wheat using natural 13C abundance method

The enhancement of soil organic carbon (SOC) is important for sustainable agriculture, while changes in SOC depend on the balance between carbon (C) input and export. To investigate how chemical fertilizers contribute to C input (e.g. plant-derived C) and export (e.g. original SOC decomposition) in soil, a wheat (a C3 plant) pot experiment was conducted using a Phaeozem that had previously been used to cultivate maize (a C4 plant). The natural 13C abundance method was used to quantify wheat-derived SOC (WSC) and microbial respiration using the original SOC (Rmicrobial) during the wheat growing season. The wheat grain, WSC, wheat-derived C (WDC: including WSC, root and stubble biomass C) and Rmicrobial-derived CO2 emission (SCE) in fertilized treatments increased by 4.8–31.1%, 48.9–122.4%, 21.3–62.2% and 6.0–51.8%, respectively, when compared to unfertilized treatments. The total SOC in the post-experimental soil increased by 0.14–0.97% when compared to pre-experimental soil because the WSC input was larger than the SCE export, and it would be increased further if wheat root and stubble biomass C were included. Therefore, application of chemical fertilizer not only directly increases crop yield, but also indirectly contributes to C sequestration by favoring crop growth and crop-derived C input in soil.

► C input and export in soil were quantified by natural 13C abundance method.
► C input was larger than C export, and led to soil organic C (SOC) increase.
► Fertilization increases SOC by favoring crop growth and crop-derived C input in soil.
► Soil CO2 fluxes were sensitive to air and soil temperatures.