title: Demand and supply of N in seed production of soybean (Glycine max) at different N fertilization levels after flowering.
abstract: Nitrogen (N) has been suggested as a determinant of seed production especially in species with high seed N content. Assuming that seed yield was determined as the balance between N demand and supply for seed production, we studied the effect of N fertilization after flowering on soybean (Glycine max L. Merr.) yield. Seed N concentration was nearly constant irrespective of N fertilization, indicating that seed production was proportional to the amount of N available for seed growth. N demand for seed production was analyzed as the product of seed number, the rate of N filling in individual seeds, and the length of the reproductive period. N fertilization increased seed number and the reproductive period, but did not influence the N filling rate. Seed number was positively correlated with dry mass productivity after flowering. Three N sources were distinguished: mineral N uptake, symbiotic N(2) fixation and N remobilization from vegetative body. N fertilization increased N uptake and N remobilization, but lowered N(2) fixation. We concluded that N availability in the reproductive period determined seed yield directly through increasing N supply for seed growth and indirectly through increasing seed N demand with enhanced plant dry mass productivity.
authors.affiliation: Tottori University, 4-101 Koyama-Minami, Tottori 680-8553, Japan. kinugasa@muses.tottori-u.ac.jp
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Kinugasa
authors.forename: Takashi
authors.initials: T
authors.lastname: Sato
authors.forename: Shimpei
authors.initials: S
authors.lastname: Oikawa
authors.forename: Tadaki
authors.initials: T
authors.lastname: Hirose
mesh_terms: D001692:Biological Transport; D018533:Biomass; D005308:Fertilizers; D035264:Flowers / Q000196:embryology / Q000502:physiology; D008954:Models, Biological; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism* / Q000494:pharmacology; D009586:Nitrogen Fixation / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D012098:Reproduction; D053204:Root Nodules, Plant / Q000254:growth & development / Q000378:metabolism; D012639:Seeds / Q000187:drug effects / Q000196:embryology / Q000378:metabolism* / Q000502:physiology; D013025:Glycine max / Q000187:drug effects / Q000196:embryology / Q000378:metabolism* / Q000502:physiology
chemical_list: D005308:Fertilizers; D009584:Nitrogen