Paddy soils have a much higher microbial biomass content than upland soils: A review of the origin, mechanisms, and drivers

Many studies have shown that the microbial biomass content in paddy soils is much higher than that in upland soils, but a comprehensive review of the underlying mechanisms and processes is lacking. We conducted a meta-analysis of published literature on the microbial biomass content in continuous paddy soils (>1700 data pairs) and paddy-upland rotation soils (>1100 data pairs) as compared to that in adjacent upland soils (>360 data pairs), measured by the fumigation extraction or fumigation incubation method. The microbial biomass carbon (MBC) content in paddy soils was double that in upland soils. This MBC surplus in paddy soils compared to upland soils was explained by (1) higher input of root C and rhizodeposits by rice plants compared with upland crops; (2) lower oxygen availability and consequently slower microbial turnover; (3) higher microbial C assimilation efficiency in paddy soils; and (4) additional C stabilization on iron (oxyhydr)oxides in paddy soils. The proportion of MBC in total soil organic C in paddy-upland rotation, paddy, and upland soils was 3.5%, 2.5%, and 2.1%, respectively. The higher microbial biomass C/N ratio in paddy soils (12.4 ± 0.11) compared to upland soils (9.9 ± 0.21) reflects greater N losses (through nitrate leaching and denitrification) in relation to slower C losses under anoxic conditions. Despite higher temperature and better water availability, microbial biomass turnover was 1.1–1.6 times slower in paddy soils than in upland soils because of oxygen limitation. Multiple stepwise regression and redundancy analyses showed that microbial biomass in continuous paddy and paddy-upland rotation soils was affected by similar soil factors (such as total N and organic C), whereas microbial biomass in upland soils was mainly affected by pH and the organic C content. Paddy-upland rotation soils undergo oxic–anoxic cycles and consequently can absorb and coprecipitate organic compounds with iron (oxyhydr)oxides as an additional advantage for C stabilization. We conclude that the reduced microbial activity and slower microbial turnover under oxygen-limited conditions lead to nearly two times higher microbial biomass content in paddy than in upland soils. © 2021 Elsevier B.V.

Wei L.1, 2 , Ge T. 1, 3 , Zhu Z.1 , Ye R.4 , Peñuelas J.5, 6 , Li Y. 1 , Lynn T.M.1 , Jones D.L.7 , Wu J.1, 2 , Kuzyakov Y. 1, 8, 9, 10
Elsevier B.V.
  • 1 Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of SciencesHunan 410125, China
  • 2 University of Chinese Academy of Sciences, Beijing, 100049, China
  • 3 State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Key Laboratory of Biotechnology in Plant Protection of Ministry of Agriculture and Zhejiang Province, Institute of Plant Virology, Ningbo University, Ningbo, 315211, China
  • 4 Department of Plant & Environmental Sciences, Pee Dee Research & Education Center, Clemson University, Florence, SC 29506, United States
  • 5 CSIC, Global Ecology Unit CREAF-CSIC-UAB, Bellaterra, Catalonia, Spain
  • 6 CREAF, Cerdanyola del Vallès, Catalonia, Spain
  • 7 School of Natural Sciences, Bangor University, Bangor, Gwynedd LL57 2UW, United Kingdom
  • 8 Department of Soil Science of Temperate Ecosystems, Department of Agricultural Soil Science, University of Gottingen, Gottingen, 37077, Germany
  • 9 Institute of Environmental Sciences, Kazan Federal University, Kazan, 420049, Russian Federation
  • 10 Agro-Technological Institute, RUDN University, Moscow, 117198, Russian Federation
Ключевые слова
Carbon sequestration; Microbial biomass and turnover; Microbial turnover; Organic matter stability; Redox changes; Rhizodeposit's utilization
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