Nitrogen fixation and soil N level during maturation affect the contents of storage compounds of soybean seeds

We compared the concentrations and contents of protein and oil in mature se eds from nodulated and non-nodulated soybean plants grown on soils with fou r different N levels during maturation. We observed a positive correlation between the contents of protein and oil in seeds from nodulated plants, See ds from nodulated plants grown on urea-treated soil showed higher protein a nd lower oil contents than those from plants grown on soil treated with coa ted slow release N fertilizer (LP-100). Contents of these compounds in seed s from nodulated plants grown on LP-100 soil were almost the same as those from non-nodulated plants on the same soil, These observations indicated th at N economy in roots during seed maturation affects the contents of storag e compounds. We suggested that the control of the N-2 fixation activity of soybean plants and management of soil N level during seed maturation are im portant to determine the contents of protein and oil in seeds.