Rhizodeposition Drives One Third of Belowground Carbon Input in Agroecosystems
Zhengjun Yan, Yuan Wen, Jie Zhou, Yakov Kuzyakov, Damien Beillouin, Johannes Lehmann, Yadong Yang, Yiqi Luo, Pete Smith, Zhaohai Zeng, Huadong ZangABSTRACT
Soil carbon (C) accumulation, an important mitigation solution to climate change, critically depends on plant C inputs. However, the allocation of belowground C inputs between root biomass and labile rhizodeposits remains poorly quantified. By synthesizing 746 global observations using 13 C/ 14 C tracing, we reveal that 17% of plant assimilated C is allocated belowground, with rhizodeposition accounting for one‐third of the net belowground C input. Legumes primarily allocate assimilated C to belowground via rhizodeposition, whereas other crops, including barley, wheat, rice, maize, and grasses, invest more in root biomass. Rhizodeposition increases with soil organic C up to a peak at 16–19 g C kg − 1 (reaching 8%–10% of assimilated C) and declines thereafter, reflecting a nonlinear relationship between soil fertility and belowground C investment. Environmental change modifies these dynamics as warming suppresses belowground C input by 36%, while drought increases rhizodeposition by 21%. Globally, wheat, maize, and rice contribute 2.70 ± 1.40, 1.76 ± 1.39, and 2.38 ± 1.78 Tg C year − 1 to belowground net C input, respectively. These findings fill critical knowledge gaps in the global C cycle and establish crop‐specific belowground C partitioning coefficients, providing updated empirical parameters to improve process‐based soil C modeling and precise C accounting for climate‐smart agriculture.