Root litterfall is the only input of organics directly to soil layers (i.e. not via the soil surface) except at ploughing when above ground residues are mixed within the ploughing depth (see section Soil Management). The amounts of carbon and nitrogen from the roots to the litter pool, CRoot→Litter and NRoot→Litter, are calculated in the section Plant Growth. Root litter fall always enters litter pool 1, even if a second litter pool is included in the simulation.