RhizoSeqC

Given concerns over climate change and food security, intensive agricultural systems face the challenge of transforming their croplands so that they store rather than emit carbon. Two approaches can be used to achieve net carbon sequestration: directly adding more carbon to soils and improving organic matter stabilisation in soils. Therefore, we must develop cropping systems capable of carrying out both these tasks that are also economically viable. RhizoSeqC will explore how carbon sequestration could be augmented by employing combinations of crops that have been bred to have higher levels of rhizodeposition, thus increasing carbon inputs. The project will also examine the effects of mineral-based carbon stabilisation mechanisms. RhizoSeqC has 6 work packages (WPs), including a coordination WP (WP0). It will explore the idea that, together, plants (WP1), bacterial communities (WP2), and mineral-associated organic matter in soils (WP3) can meet agricultural demands (WP4) while also boosting soil carbon sequestration (WP5). The project will focus on sorghum, a cereal and forage crop of agricultural interest: it can contribute to food security and handle the effects of climate change (water stress and warming). Arenosols were chosen as the reference soil type for WP comparisons because of their naturally poor levels of organic matter content and their broad occurrence across the Global North and South. During WP4, testing will occur on other soil types. WP1 will focus on sorghum rhizodeposition and will identify genomic regions (QTLs) that control the amount of soil organic matter released into the soil. Variety breeding will optimise the formation of rhizodeposits around the roots. In WP2, the project will use stable isotope tracing and omics approaches to assess the impacts of rhizodeposition on microbial communities and on carbon-to-nitrogen stoichiometry in biotransformations. Particular attention will be paid to the priming effect, which could have a negative influence by reducing the initial carbon stocks. WP3 will explore the fate of rhizodeposited carbon in different soil types and the stabilising effects of mineral-associated organic matter. Isotopic labelling will be used to estimate the carbon balance (input/output/net gain) and to monitor carbon fate using in situ imaging techniques. WP4 will evaluate the agricultural properties of sorghum lines bred at experimental sites with contrasting climatic conditions (in France and Senegal). WP5 will draw upon the results of the first four WPs by applying them in the field. It will accurately quantify carbon sequestration using isotopic methods and predict carbon sequestration using modelling. With its 11 partners, RhizoSeqC is building a multidisciplinary community of scientists and operational stakeholders at national and international levels across the Global North and South. The research institutes involved are CNRS, IRD, CIRAD, INRAE, and ISRA (INRAE’s counterpart in Senegal), CEA, ENS, and two universities (Rouen and Paris Sciences et Lettres). RhizoSeqC’s work mainly corresponds to FairCarboN’s axis 3 priorities: (1) increasing carbon stocks in soils; (2) better quantifying how plant roots and rhizospheres effectively contribute to organic matter sequestration; and (3) identifying crop production solutions adapted to future climatic conditions. RhizoSeqC’s results should help inform agroecological innovations in cereal-growing systems in both the Global North and South. These innovations will enhance carbon sequestration in soils and thus help to achieve carbon neutrality while also preparing for future climate constraints.