Linking phosphorus and carbon in rhizosphere nutrient cycling
EMSL Project ID
50395
Abstract
Plant root exudates provide a significant carbon (C) source for rhizosphere microbial communities. In return, these communities help mobilize nutrients needed for plant growth. For instance, biogeochemical cycling of phosphorus (P) in the rhizosphere is directed by a suite of bacterial, fungal, and root processes acting on geochemical sources of P which themselves are heterogeneously distributed in soil. While previous studies have identified increased root exudation as one strategy plants use to stimulate P mobilization in response to limitation, most of these studies were at the larger, integrated scale and not spatially focused. We hypothesize that spatial localization of root exudation is used to maximize P return to a plant by leveraging dispersed microbial and geochemical microenvironments within the rhizosphere. We propose to evaluate this hypothesis using switchgrass microcosms in an effort to better understand the fundamental controls of nutrient delivery from soil to this bioenergy crop. Enhanced understanding of the linkages between C and P cycling in the rhizosphere will support switchgrass growth from marginal lands in support of DOE's mission focus in bioenergy production.
We will use a series of spatially-specific measurements to track the linkage between plant C delivery to and the resulting P mobilization within the rhizosphere. We will implant P resource islands within our microcosms and initially track root response to the added resource. We will then use 13C labeling with a number of spatially-resolved techniques to track plant uptake of CO2 and release of resulting organic C through root exudation. We will identify spatial foci of root exudation and track the dominant microbial taxa active in these locations. We will then map the total and bioavailable P pools and determine how the locations of these pools relate to both plant and microbial activity. We anticipate observing spatial correlation between C delivery and P bioavailability within the rhizosphere.
Taken together, our planned analyses will leverage spatial assessment to better understand the linkage between C delivery and consumption within the rhizosphere and resulting nutrient (P) mobilization to support plant growth. While P can be fairly abundant in many soils, most of this P is not bioavailable and thus does not stimulate plant biomass production. Fertilizer application can be used to circumvent P limitations. However, economic constraints, concerns over environmental impact, and fundamental limits in P reserves suitable for mining can limit future P application to soils. A better understanding of interactions between plants, microbial communities, and the geochemical environments within the rhizosphere will be able to guide future efforts to improve P delivery from natural soils to bioenergy crops and thereby improve the viability of biomass production on marginal lands.
Project Details
Project type
FICUS Research
Start Date
2018-10-01
End Date
2021-03-31
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Velickovic D., V.S. Lin, A. Rivas-Ubach, C.R. Anderton, and J.J. Moran. 2020. "An approach for broad molecular imaging of the root-soil interface via indirect matrix-assisted laser desorption/ionization mass spectrometry." Soil Biology and Biochemistry 146. PNNL-SA-150080. doi:10.1016/j.soilbio.2020.107804