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Coupling root dynamics with reactive transport processes in soil-method and example application to phosphorus acquisition from a mineral source in alkaline
soils
Frédéric Gérard, Céline Blitz, Philippe Hinsinger, Loïc Pagès
To cite this version:
Frédéric Gérard, Céline Blitz, Philippe Hinsinger, Loïc Pagès. Coupling root dynamics with reactive transport processes in soil-method and example application to phosphorus acquisition from a mineral source in alkaline soils: Method and example application to phosphorus acquisition from a mineral source. 5. International EcoSummit: Ecological Sustainability: Engineering Change, Aug 2016, Montpellier, France. 2016. �hal-02739636�
Coupling root dynamics with reactive transport processes in soil
Method and example application to phosphorus acquisition from a mineral source
Introduction
Methods
Results
Conclusions
Frédéric Gérard1, Céline Blitz1, Philippe Hinsinger1, and Loïc Pagès2
1. INRA, UMR Eco&Sols, 34060 Montpellier; [email protected]), 2. INRA, UMR PSH, 84914 Avignon
Acknowledgements: The coupling of Min3P and ArchiSimple was performed thanks to the financial support of SYNGENTA Crop
protection (Stein, Suisse) within the framework of the project ‘Pestdynasolroot’ with INRA. The authors are indebted to N. Moitrier for his technical advises on Fortran-C++ interoperability.
References
Our objectives were two-fold (Gérard et al., 2016):
(1) To develop a soil-plant model that comprehensively describe geochemical processes.
(2) To illustrate its relevance for studying soil-plant interactions. We investigated for illustration purposes the problem of P acquisition from a mineral P source as mediated by nutrient uptake and pH changes in the rhizosphere. This is an important ecological process for the sustainable intensification of agro-ecosystems (e.g. Richardson et al. 2011).
The root system model
ArchiSimple (Pagès et al., 2014)
Sequential coupling + data exchange at a daily time step
Macroscopic approach - Root
segments converted into a root surface density in each grid block.
The reactive transport model Min3P (e.g. Mayer et al., 2012)
Alkaline soil Growth of a typical root
system for monocots
Nutrient uptake (Ca/P = 1.5) H+/OH- release (K+ vs. NO 3 -uptake) Equilibrium with hydroxyapatite
Cation and anion
adsorption/desorption
Low P availability (0.1 µM)
Root-induced alkalization Root-induced acidification
P uptake whole plant over time Model Min3P-ArchiSimple
Modelling conditions
+
Root system ArchiSimple
z
(
m
)
Root surface density (m2 m-3)
0 2 4 6 Dissolved P (mol L-1) 1.10-7 1.10-8 5.10-8 x (m) x (m) x (m) z ( m ) z ( m ) pH 8.2 7.8 7.5 8.0
HA dissolution rate (mol day-1)
P uptake rate (mol day-1)
4.10-9 7.10-7 1.4.10-6 -1.10-9 -2.10-7 -4.10-7 x (m) x (m) x (m) 0.E+00 1.E-02 2.E-02 3.E-02 4.E-02 5.E-02 20 30 40 50 60 70 80 Time (days) P u p ta k e ( m o l/ p la n t) Acidification Alkalization No mineral P z ( m ) z ( m ) z ( m ) z ( m ) z ( m ) 0 2 4 6 1.10-7 1.10-6 2.10-6 6.8 7.2 7.5 7.0 1.10-7 2.10-5 4.10-5 -1.10-7 -5.10-6 -1.10-5
Root system ArchiSimple
pH P uptake rate (mol day-1) HA dissolution rate (mol day-1)
x (m) x (m) x (m) x (m) x (m) x (m) z ( m ) z ( m )
Root surface density (m2 m-3) Dissolved P (mol L-1)
We developed an innovative soil-root system model that comprehensively describes chemical processes (reaction thermodynamics and kinetics) coupled with mass transport processes.
The present application showed that most of the plant P can be issued from hydroxyapatite when root-induced alkalization occurs, thanks to the influence of Ca and P uptake, and confirmed that acidification is much more efficient.
•Dunbabin V M, Postma J A, Schnepf A, Pages L, Javaux M, Wu L H, Leitner D, Chen Y L, Rengel Z and Diggle A J 2013 Modelling root-soil interactions using three-dimensional models of root growth, architecture and function. Plant and Soil 372, 93-124.
•Gérard F, Blitz C, Hinsinger P and Pagès L 2016 Modelling the interactions between root system architecture, root functions and reactive transport processes in soil. Plant & Soil Submitted.
•Mayer K U, Amos R T, Molins S and Gérard F 2012 Reactive transport modeling in variably saturated media with MIN3P: Basic model formulation and model enhancements. In Groundwater reactive transport models, Eds F Zhang, G T Yeh, J C Parker and X Shi. pp 187-212. Bentham Science Publishers Ltd.
•Pagès L, Becel C, Boukcim H, Moreau D, Nguyen C and Voisin A S 2014 Calibration and evaluation of ArchiSimple, a simple model of root system architecture. Ecological Modelling 290, 76-84.
•Richardson A E, Lynch J P, Ryan P R, Delhaize E, Smith F A, Smith S E, Harvey P R, Ryan M H, Veneklaas E J, Lambers H, Oberson A, Culvenor R A and Simpson R J 2011 Plant and microbial strategies to improve the phosphorus efficiency of agriculture. Plant and Soil 349, 121-156.
Numerical models that couple root systems and related functions with soil processes are limited with respect to the description of reactive transport processes in soil, particularly with respect to soil chemistry. For example, aqueous speciation is not taken into account (e.g. Dunbabin et al., 2013). This lack precludes with a comprehensive modelling of soil chemistry using chemical thermodynamic and kinetic principles (e.g. law of mass action, chemical affinity).
