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

authored by

Juanjuan Ai, Callum C. Banfield, Guodong Shao, Kazem Zamanian, Tobias Stürzebecher, Lingling Shi, Lichao Fan, Xia Liu, Sandra Spielvogel, Michaela A. Dippold

Abstract

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.

Organisation(s)

Institute of Soil Science

External Organisation(s)

Shandong Academy of Agricultural Sciences
Shandong Normal University
University of Tübingen
University of Göttingen
Nanjing University of Information Science and Technology
Northwest Agriculture and Forestry University
Kiel University

Type

Article

Journal

Soil Biology and Biochemistry

Volume

185

ISSN

0038-0717

Publication date

10.2023

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Microbiology, Soil Science

Sustainable Development Goals

SDG 2 - Zero Hunger

Electronic version(s)

https://doi.org/10.1016/j.soilbio.2023.109129 (Access: Closed)