Rhizodeposition through root senescence and root exudation of atmospheric C and N by legumes is controlled by traits indicative of resource acquisition and root development

Legume crop production has many benefits for agricultural systems. Through the rhizodeposition process, they release a significant amount of C and N into the soil, increasing soil organic C and reducing the use of N fertilizer. Rhizodeposition is known as a dynamic process influenced by many factors. The aim of this study was to study the contribution of root exudation and root senescence to the rhizodeposition of atmospheric C and N during vegetative and reproductive growth in annual and perennial legumes and to understand how this is linked to the fixation capacities of C and N and root functional traits. An original approach that combined 13CO2 labeling and the 15N dilution method was developed to measure the rhizodeposition of atmospheric C and N throughout plant growth by two annual grain legumes (pea and faba bean) and two perennial forage legumes (white and crimson clovers). C rhizodeposition was found to increase proportionally with N rhizodeposition during reproductive develop..., Two annual grain legumes and two perennial forage legumes were grown and labeled with 13CO2 to measure fixation (Total fixed C, g/m2) and rhizodeposition (CdfR, g/m2) of photosynthetically fixed C. The 15N dilution method was used to measure biological N fixation (Ndfa, g/m2) and transfer of N (NdfR, g/m2) from the atmosphere to the soil. Root traits were also measured with the winrhizo method: (1) total shoot and root dry biomass (g), (2) root mass ratio (RMR ;Â g/g), the ratio of root dry mass to total plant dry mass, (3) root dry matter content (RDMC; mg/g), the ratio of total root dry biomass to total root fresh biomass, (4) root tissue density (RTD ; mg/cm3), the ratio of root dry biomass to total root volume, (5) root diameter corresponding to the mean diameter of the total root system, (6) specific root length (SRL; m/g), the ratio between total root length and dry biomass, (7) root C content (RCC ; mg/g), the ratio of amount of root C to root dry mass, (8) root N content (RNC ; ..., All data are expressed here in a csv format