Influence of Nitrogen Accumulation and Redistribution on Seed Yield in Soybean during Seed Filling

It is well known that soybean plants need to take up large amount of nitrogen for its high content of protein. Generally the seed yield of soybean does not respond to the nitrogen fertilization clearly, because soybean plants could acquire nitrogen from nodules by nitrogen fixation. Therefore, the importance of nitrogen fertilization in soybean production is not well considered. However, the cost of nitrogen fixation is the consumption of assimilate, indicating the competition in assimilate between nitrogen fixation and seed production. This paper reviewed the functions of nitrogen accumulation and redistribution during seed filling and its relationship with seed yield in soybean, based on our recent works and published reports. It indicated that nitrogen remobilization from vegetative organs to seeds during seed filling could support the seed yield, while it also results in the earlier plant senescence, shortens the seed filling duration, and thus limits seed production. This review provides some information relating with the functions of nitrogen accumulation and redistribution during seed filling, and guidelines for how to use nitrogen fertilizer effectively for high seed yielding soybean production.