TY - JOUR

T1 - What controls the availability of organic and inorganic P sources in top- and subsoils? A 33P isotopic labeling study with root exudate addition

AU - Ai, Juanjuan

AU - Banfield, Callum C.

AU - Shao, Guodong

AU - Zamanian, Kazem

AU - Stürzebecher, Tobias

AU - Shi, Lingling

AU - Fan, Lichao

AU - Liu, Xia

AU - Spielvogel, Sandra

AU - Dippold, Michaela A.

N1 - Funding Information: This work was financially supported by the project “RootWays” (project number: 031B0911C ) of the BMBF funded Rhizo4Bio initative coordinated by the BONARES center. Michaela Dippold was funded by the Robert-Bosch- Foundation (More crop per drop for sub-Saharan Africa). Kazem Zamanian was funded by Research Fund for International Young Scientists of National Natural Science Foundation of China (NSFC) ( 42050410320 ), and Xia Liu funded by Shandong Provincial Major Scientific and Technological Innovation Project ( 2022CXGC010607 ), Shandong Provincial “Bohai Granary” Science and Technology Demonstration Project ( 2019BHLC003 ), Shandong Provincial Agricultural Major Applied Technology Innovation Project ( SD2019ZZ013 ). We gratefully acknowledge the funding by the Bayer Foundation for Juanjuan Ai. We also thank the China Scholarship Council (CSC) for funding Juanjuan Ai's stay in Germany. The authors would like to thank Meisam Nazari for providing maize mucilage, and also Xiaona Song, Jie Zhou, Xuechen Zhang for help and support during data analysis, Karin Schmidt and Susann Enzmann for laboratory assistance.

PY - 2023/10

Y1 - 2023/10

N2 - Phosphorus (P) is a major limiting nutrient for plant growth implying an often-intensive competition between microorganisms and plants in the rhizosphere. Increasing the P availability in subsoils may help to mitigate potential future P fertilizer shortages and to overcome P limitations due to droughts, which mainly affect topsoils. Root exudates provide easily available carbon and energy sources for microorganisms to mobilize soil nutrients. Nonetheless, details regarding the distinct processes underlying P mobilization from various P sources (free vs. sorbed PO43−; low molecular vs. complex organic P, e.g. ATP vs. plant litter P) as affected by root exudates are poorly understood, especially in subsoils. This study aimed to identify the controlling factors and microbial processes regulating the availability of organic and inorganic P in top- and subsoils by 33P isotopic labeling. The focus was on the potential key role of root exudates in P mobilization. We found that microbial communities in top- and subsoils used high- and low-available mineral P to a similar extent, but that the subsoil communities were much more efficient in mobilizing and incorporating complex litter-derived organic P. This capability of subsoil communities was even enhanced when root exudates were present. Microbial activity and nutrient-mobilizing mechanisms (e.g., P-related enzymes) clearly increased by root exudate addition, an effect that was generally higher in sub-than in topsoils. We conclude that subsoil communities are well capable of mobilizing and using complex organic P sources, especially if root exudates accelerate overall activity and P cycling. Thus, high root exudation is highly relevant for crops, which depend on subsoil nutrients and litter-derived P. Accordingly, detritusphere P, e.g. in subsoil root channels, is likely to be plant-available because of exudate-induced microbial P (re-)cycling processes.

AB - Phosphorus (P) is a major limiting nutrient for plant growth implying an often-intensive competition between microorganisms and plants in the rhizosphere. Increasing the P availability in subsoils may help to mitigate potential future P fertilizer shortages and to overcome P limitations due to droughts, which mainly affect topsoils. Root exudates provide easily available carbon and energy sources for microorganisms to mobilize soil nutrients. Nonetheless, details regarding the distinct processes underlying P mobilization from various P sources (free vs. sorbed PO43−; low molecular vs. complex organic P, e.g. ATP vs. plant litter P) as affected by root exudates are poorly understood, especially in subsoils. This study aimed to identify the controlling factors and microbial processes regulating the availability of organic and inorganic P in top- and subsoils by 33P isotopic labeling. The focus was on the potential key role of root exudates in P mobilization. We found that microbial communities in top- and subsoils used high- and low-available mineral P to a similar extent, but that the subsoil communities were much more efficient in mobilizing and incorporating complex litter-derived organic P. This capability of subsoil communities was even enhanced when root exudates were present. Microbial activity and nutrient-mobilizing mechanisms (e.g., P-related enzymes) clearly increased by root exudate addition, an effect that was generally higher in sub-than in topsoils. We conclude that subsoil communities are well capable of mobilizing and using complex organic P sources, especially if root exudates accelerate overall activity and P cycling. Thus, high root exudation is highly relevant for crops, which depend on subsoil nutrients and litter-derived P. Accordingly, detritusphere P, e.g. in subsoil root channels, is likely to be plant-available because of exudate-induced microbial P (re-)cycling processes.

KW - P labeling

KW - Enzyme activity

KW - Microbial biomass

KW - Microbial community

KW - Root exudates

KW - Subsoil

UR - http://www.scopus.com/inward/record.url?scp=85166655219&partnerID=8YFLogxK

U2 - 10.1016/j.soilbio.2023.109129

DO - 10.1016/j.soilbio.2023.109129

M3 - Article

AN - SCOPUS:85166655219

VL - 185

JO - Soil Biology and Biochemistry

JF - Soil Biology and Biochemistry

SN - 0038-0717

M1 - 109129

ER -