01762naa a2200157 a 450000100080000000500110000800800410001910000200006024500550008026000090013552013280014470000180147270000170149070000220150777300750152914690462004-11-23       2003    bl ---       0--  u    #d1 aSINCLAIR, T. R.  aModeling nitrogen accumulation and use by soybean.  c2003  aSimulation of soybean growth and yield requires an accurate representation of nitrogen accumulation and distribution in the developing crop. Approaches to simulate nitrogen accumulation by soybean have been complicated by the need to account for both soil nitrate uptake and symbiotic nitrogen fixation. Past approaches to simulating soybean have generally been empirical requiring ?calibration? for each new environment. Recently, Jamieson and Semonov [Field Crops Res. 68 (2000) 21] proposed a relatively simple approach for simulating nitrogen accumulation by wheat based on the nitrogen demand imposed separately by the development of leaf area and the growth of stems. This paper assesses this approach for soybean. This approach was further simplified by assuming that nitrogen availability to the plant was limited only by soil moisture conditions and a maximum uptake rate and that it was not necessary to distinguish between nitrate uptake and symbiotic nitrogen fixation. The simplified model generally resulted in simulations that corresponded to experimental observations on nitrogen and mass accumulation through the growing season, and on yield over a number of years. Sensitivity analysis of the model indicated that storage of nitrogen in the stem might be a key trait in increasing soybean yield potential.1 aFARIAS, J. R.1 aNEUMAIER, N.1 aNEPOMUCENO, A. L.  tField Crops Research, Amsterdamgv. 81, n. 2/3, p. 149-158, Feb. 2003.