Microbial iron reduction compensates for phosphorus limitation in paddy soils

authored by
Chaoqun Wang, Lukas Thielemann, Michaela A Dippold, Georg Guggenberger, Yakov Kuzyakov, Callum C Banfield, Tida Ge, Stephanie Guenther, Patrick Bork, Marcus A Horn, Maxim Dorodnikov

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.

Institute of Soil Science
Institute of Microbiology
External Organisation(s)
University of Göttingen
University of Tübingen
Ningbo University
Science of the Total Environment
Publication date
Publication status
Peer reviewed
ASJC Scopus subject areas
Environmental Engineering, Environmental Chemistry, Waste Management and Disposal, Pollution
Sustainable Development Goals
SDG 15 - Life on Land
Electronic version(s)
https://doi.org/10.1016/j.scitotenv.2022.155810 (Access: Closed)