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Rhizodeposition efficiency of pearl millet genotypes assessed on short growing period by carbon isotopes (δ13C and F14C)
Soil  (IF5.841),  Pub Date : 2021-09-28, DOI: 10.5194/soil-2021-108
Papa Mamadou Sitor Ndour, Christine Hatté, Wafa Achouak, Thierry Heulin, Laurent Cournac

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 days of growth under semi controlled condition. The Soil organic carbon (SOC) content, δ13C and F14C of soil samples were measured, and the plant-derived C amount and Clost / Cnew ratio in 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 to the soil at early stage of pearl millet growth. The concentration of plant-derived C in 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 was more important for the low-aggregation lines than for the high-aggregation ones indicating a better C sequestration potential of these latter.