Allocation of photosynthesized carbon in an intensively farmed winter wheat–soil system as revealed by (14)CO(2) pulse labelling

Understanding the rhizodeposited carbon (C) dynamics of winter wheat (Triticum aestivum L.), is crucial for soil fertility and C sequestration. Pot-grown winter wheat was pulse labelled with (14)CO(2) at the key growth stages. (14)C in the shoots, roots and soil was measured at 5 or 2 days after (14)C-labelling (DAL 5/2) at each growth stage and at harvest. The (14)C in the shoots increased from 4% of the net (14)C recovered (shoots + roots + soil) during tillering to 53% at harvest. Approximately 14–34% of the net (14)C recovered was incorporated into the soil. Allocation of photosynthesized C was extrapolated from the pot experiment to field condition, assuming a planting density of 1.8 million plants ha(−1). The estimated C input to the soil was 1.7 t C ha(−1), and 0.7 t C ha(−1) of root residues was retained after wheat harvest; both values were higher than those previously reported (0.6 and 0.4 t C ha(−1), respectively). Our findings highlight that C tracing during the entire crop season is necessary to quantify the temporal allocation of photosynthesized C, especially the contribution to soil carbon in intensified farming system.