G05_03

Global warming mitigation capacity of plant lines assessed by ¹³C and ¹⁴C. The case of rhizodeposition efficiency of pearl millet.

HATTÉ C^1,2,  SITOR NDOUR P^3,4, ACHOUAK W⁵, HEULIN T⁵, COURNAC L³

¹LSCE - CEA, Gif-sur-Yvette, France, ²Silesian University of Technology, Gliwice, Poland, ³Eco&Sols, Montpellier, France, ⁴Mohammed VI Polytechnic University, Ben Guerir, Morocco, ⁵LEMIRE BIAM, 13115 Saint-Paul-Lez-Durance, France

In the context of climate change, a new challenge for agriculture is to sequester more carbon in the soil to mitigate CO₂ increase in the atmosphere. Then, plant breeding for root traits (architecture and root exudation) could be an original strategy to enhance SOC sequestration.

In order to evaluate how it may contribute to the carbon sequestration objective, the carbon input into the soil should be determined. However, due to the heterogeneous nature of the soil and particularly in-field conditions, conventional carbon measurement methods could not answer this question in short-term experiments such as those used for screening plant genotypes. The change in carbon concentration would remain below the natural variability. Furthermore, the so-called priming effect that contributes to extra mineralization of molecules derived from soil old carbon, has also to be evaluated.

As an alternative method, we’ve measured carbon deposition in the pearl millet (Pennisetum glaucum) rhizosphere using carbon isotopes (¹³C and ¹⁴C) that are much less sensitive to soil heterogeneity. This is furthermore indicative of the age of the primed carbon. Four pearl millet lines were tested and associated soil was analyzed after only one month of growth. Using a conceptual model, we evidenced a priming effect for all pearl millet lines. Importantly, the priming effect amplitude was higher for the small rhizosheath (low-aggregation) line than for the large rhizosheath (high-aggregation) ones, indicating a better carbon sequestration potential of the latter.