Nitrogen nutrition, yield and protein content in soybean

Soybean recombinant inbred lines derived from a cross between two cultivars of different genetic origins, each with a high seed protein content? were analyzed for their dinitrogen fixation and nitrate assimilation abilities and for their seed traits. The influence of both nitrogen sources on yield and protein content was evaluated. The importance of symbiotic N-2 fixation in yield and seed protein content was corroborated. Dinitrogen fixation efficiency during the reproductive growth period until late stages (R2-R6 + 10 d) is involved in seed protein content. The yield is more directly related to mineral nitrogen assimilation in the first stages of the reproductive growth period (R2) and to high dinitrogen fixation rates at stage R6. Nitrogen nutrition abilities are independent and can be used as complementary criteria when selecting for agronomic seed traits. (C) 2000 Published by Elsevier Science Ireland Ltd. All rights reserved.