Rhizodeposition efficiency of pearl millet genotypes assessed on a short growing period by carbon isotopes (<i>δ</i><sup>13</sup>C and F<sup>14</sup>C)
Author:
Ndour Papa Mamadou SitorORCID, Hatté ChristineORCID, Achouak Wafa, Heulin Thierry, Cournac Laurent
Abstract
Abstract. Rhizosheath size varies significantly with crop genotype,
and root exudation is one among its driving factors. Unravelling the
relationships between rhizosheath formation, root exudation and soil carbon
dynamics may bring interesting perspectives in terms of crop breeding
towards sustainable agriculture. Here we grew four pearl millet (C4
plant type: δ13C of −12.8 ‰, F14C = 1.012) inbred lines showing contrasting rhizosheath sizes in a C3 soil
type (organic matter with δ13C of −22.3 ‰,
F14C = 1.045). We sampled the root-adhering soil (RAS) and bulk soil
after 28 d of growth under a semi-controlled condition. The soil organic carbon (SOC) content and δ13C and F14C of soil samples were measured and the plant-derived C amount and Clost / Cnew ratio in the RAS were calculated. The results showed a significant increase in δ13C in the RAS of the four pearl millet lines compared to the control
soil, suggesting that this approach was able to detect plant C input into the soil at an early stage of pearl millet growth. The concentration of
plant-derived C in the RAS did not vary significantly between pearl millet
lines, but the absolute amount of plant-derived C varied significantly when
we considered the RAS mass of these different lines. Using a conceptual
model and data from the two carbon isotopes' measurements, we evidenced a priming effect for all pearl millet lines. Importantly, the priming effect amplitude (Clost / Cnew ratio) was higher for the small rhizosheath
(low-aggregation) line than for the large rhizosheath (high-aggregation)
ones, indicating a better C sequestration potential of the latter.
Funder
Agence Nationale de la Recherche Commissariat à l'Énergie Atomique et aux Énergies Alternatives
Publisher
Copernicus GmbH
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