Reduced belowground allocation of freshly assimilated C contributes to negative plant-soil feedback in successive winter wheat rotations

Abstract

Aims Successively grown winter wheat (WW) is associated with yield reduction, often attributed to the unfavorable soil microbes that persist in the soil through plant residues. How rotational positions of WW affect the allocation of freshly assimilated carbon (C) above and belowground remains largely unknown. Methods A 13CO2 pulse labeling rhizotron experiment was conducted in the greenhouse. WW was grown in soil after oilseed rape (W1), after one season of WW (W2), and after three successive seasons of WW (W4). We used an automatic manifold system to measure the δ13C of soil CO2 at six depths and five different dates. δ13C was measured in the dissolved organic C (DOC), microbial and plant biomass pools. Results Rotational position strongly influenced the root-derived C. Higher δ13C was found in the soil CO2 of W1 compared to W4, especially in the topsoil during the late growth stage. Higher DOC and microbial δ13C was traced in W1 and W4 compared to W2. The WW biomass was more enriched in 13C in W1 compared to W2 and W4. Conclusions Our study demonstrates a potential mechanism through which the rotational position of WW can affect the allocation of freshly fixed C above and belowground.