Microbial iron reduction compensates for phosphorus limitation in paddy soils

Limitation of rice growth by low phosphorus (P) availability is a widespread problem in tropical and subtropical soils because of the high content of iron (Fe) (oxyhydr)oxides. Ferric iron-bound P (Fe(III)-P) can serve as a P source in paddies after Fe(III) reduction to Fe(II) and corresponding H2PO4− release. However, the relevance of reductive dissolution of Fe(III)-P for plant and microbial P uptake is still an open question. To quantify this, 32P-labeled ferrihydrite (30.8 mg P kg−1) was added to paddy soil mesocosms with rice to trace the P uptake by microorganisms and plants after Fe(III) reduction. Nearly 2% of 32P was recovered in rice plants, contributing 12% of the total P content in rice shoots and roots after 33 days. In contrast, 32P recovery in microbial biomass decreased from 0.5% to 0.08% of 32P between 10 and 33 days after rice transplantation. Microbial biomass carbon (MBC) and dissolved organic C content decreased from day 10 to 33 by 8–54% and 68–77%, respectively, suggesting that the microbial-mediated Fe(III) reduction was C-limited. The much faster decrease of MBC in rooted (by 54%) vs. bulk soil (8–36%) reflects very fast microbial turnover in the rice rhizosphere (high C and oxygen inputs) resulting in the mineralization of the microbial necromass. In conclusion, Fe(III)-P can serve as small but a relevant P source for rice production and could partly compensate plant P demand. Therefore, the P fertilization strategies should consider the P mobilization from Fe (oxyhydr)oxides in flooded paddy soils during rice growth. An increase in C availability for microorganisms in the rhizosphere intensifies P mobilization, which is especially critical at early stages of rice growth. © 2022 Elsevier B.V.

Wang C.1 , Thielemann L.1 , Dippold M.A.1, 2 , Guggenberger G.3 , Kuzyakov Y. 4, 5, 6 , Banfield C.C.1, 2 , Ge T. 7 , Guenther S.3 , Bork P.8 , Horn M.A.8 , Dorodnikov M.1, 4
Elsevier B.V.
  • 1 Biogeochemistry of Agroecosystems, University of Goettingen, Goettingen, 37077, Germany
  • 2 Geo-Biosphere Interactions, University of Tuebingen, Tuebingen, 72076, Germany
  • 3 Institute of Soil Science, Leibniz University Hannover, Hannover, 30419, Germany
  • 4 Department of Soil Science of Temperate Ecosystems, University of Goettingen, Goettingen, 37077, Germany
  • 5 Agricultural Soil Science, University of Goettingen, Goettingen, 37077, Germany
  • 6 Peoples Friendship University of Russia (RUDN University), Moscow, 117198, Russian Federation
  • 7 State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, Institute of Plant Virology, Ningbo University, Zhejiang, Ningbo, 315211, China
  • 8 Institute of Microbiology, Leibniz University Hannover, Hannover, 30419, Germany
Ключевые слова
Ferric iron reduction; Land use in subtropics; Phosphorus isotopes; Phosphorus pools and availability; Plant-microbial competition; Redox potential
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