SimTraces : A Numerical simulator for predicting the accumulation of Trace Elements (TE's) by crops

Accumulation of soil trace elements by cultivated plants is a threat for food and feed quality but on the other hand, it is also a valuable solution for cleaning-up polluted soils. In order to guarantee the quality of crops or to optimize phytoextraction, it is necessary to identify the key mechanisms that govern the geochemistry of the trace elements in soils, their uptake by a growing root system and their partitioning between plant organs.

The main objective of the SimTrace project is to integrate all the key mechanisms governing the accumulation of trace elements in plant parts into a simulation model that also considers the environmental conditions of the crop : climate, and agricultural practices.

Besides being a scientific tool, the simulation model should allow farmers and environmental stakeholders not only to assess the risk that crops do not comply the regulations for their content in trace elements but also to test scenarios of agricultural practices in order i) to make the crops comply with the regulation and ii) to optimize the phytoextraction of trace elements from polluted soils by dedicated crops.

SimTraces is a research project dedicated to be transferred to applications in the field. It has been coordinated by UMR 1391 INRA ISPA (Ch. Nguyen). It relied on a scientific consortium of five INRA groups (UMR ISPA Bordeaux, LSE Nancy, PSH, Agroclim and BioSP, Avignon). The project started in January 2012 and lasted four years and a half.

SimTraces was funded by the French National Research Agency (ANR) (448 810€) and the total cost was around 2 663 964€.

The key feature of the SimTraces project is to integrate knowledges in soil science, geochemistry, plant ecophysiology and crop science. The main mechanisms governing the transfer of trace elements from soil to plant organs have first been conceptualized and then modeled mathematically : availability of trace element in soil (Working Package 1), uptake by the growing root system (including root architecture (Working Package 2) and partitioning between plant organs along with plant growth (Working Package 3).

Theses models were coupled together and  to the Stics crop model in order to consider the effect of climate and of the agricultural practices on the plant growth. The whole is the SimTraces model that can be used to manage crops for optimizing crop quality or phytoextraction efficiency (Working Package 4).

The project focussed on cadmium (Cd) as a model trace element, on sunflower Helianthus annuus and on the hyperaccumulator Alpine Penny-cress Noccea caerulescens as plant models for crop quality and phytoextraction, respectively.

Thanks to the power of computer-assisted intensive calculation, it was possible to perform a huge number of simulations in order to rank input variables, to test hypotheses, to understand the relative importance of the mechanisms.

The SimTraces integrated model and submodels (phytoavailability, uptake, partitioning) will soon be available as a R package.