Carbon input and allocation by rice into paddy soils: A review

Knowledge of belowground C input by rice plants and its fate is essential for managing C cycling and sequestration in paddy soils. Previous reviews have summarized C input and the pathways of root-derived C in upland soils by labeling with 14 C or 13 C ( 13/14 C), while rice rhizodeposition and C input in paddy soils have not been comprehensively evaluated. Here, we analyzed the results of 13/14 C pulse and continuous labeling studies using 112 datasets from 13 articles on the allocation and pathways of photosynthesized C by rice plants to assess C input, budget, and amount stabilized in paddy soils. Overall, 13/14 C partitioning estimated by continuous labeling was 72% to the shoots, 17% to the roots, 10% to the soil, and 1.3% was recovered in microbial biomass. Pulse-labeling studies showed a similar C partitioning: 79%, 13%, 5.5%, and 2.1%, respectively. The total belowground C input estimated based on continuous labeling was 1.6 Mg ha −1 after one rice season, of which rhizodeposition accounted for 0.4 Mg C ha −1 . Carbon input assessed by pulse labeling was slightly lower (total belowground C input, 1.4 Mg ha −1 ; rhizodeposition, 0.3 Mg C ha −1 ; 14 days after labeling). Rice C input after one cropping season was lower than that by upland plants (cereals and grasses, 1.5–2.2 Mg ha −1 ). In contrast to upland crops, most paddy systems are located in the subtropics and tropics and have two or three cropping seasons per year. We conclude that (1) pulse labeling underestimates the total belowground C input by 15%, compared with that by continuous labeling, and (2) rhizodeposition of rice accounts for approximately 26% of the total belowground C input, regardless of the labeling method used. Based on allocation ratios, we suggest a simple and practical approach for assessment of the gross C input by rice into the soil, for partitioning among pools and for long-term C stabilization in paddies. © 2019 Elsevier Ltd

Liu Y.1, 2 , Ge T.1 , Zhu Z.1 , Liu S.1 , Luo Y.3 , Li Y.1 , Wang P.2 , Gavrichkova O. 4, 5 , Xu X.6 , Wang J.2 , Wu J.1 , Guggenberger G.1, 7 , Kuzyakov Y. 1, 4, 8
Elsevier Ltd
  • 1 Key Laboratory of Agro-ecological Processes in Subtropical Regions and Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of SciencesHunan 410125, China
  • 2 Key Laboratory of Arable Land Conservation (Northeast China), Ministry of Agriculture and National Engineering Laboratory for Efficient Utilization of Soil and Fertilizer Resources, College of Land and Environment, Shenyang Agricultural University, Shenyang, Liaoning 110866, China
  • 3 Institute of Soil and Water Resources and Environmental Science, Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, 310058, China
  • 4 Agro-Technology Institute, RUDN University, Moscow, Russian Federation
  • 5 Institute of Research on Terrestrial Ecosystems, National Research Council, Porano and Montelibretti, Italy
  • 6 Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
  • 7 Institute of Soil Science, Leibniz Universität Hannover, Hannover, 30419, Germany
  • 8 Department of Soil Science of Temperate Ecosystems, Department of Agricultural Soil Science, University of Goettingen, Goettingen, 37077, Germany
Belowground assimilate allocation; Carbon cycling; Carbon isotope labeling; Carbon sequestration; Rhizodeposition and root exudation; Rice production
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