Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: November 12, 2006
Publication Date: N/A
Technical Abstract: Active and passive uptake mechanisms are important for nitrogen (N) uptake in plants. Active uptake includes N entering a plant via a diffusive flow process in the roots. This process is believed to be controlled by the plant and depends on plant demand for N. Passive uptake includes N that enters the plant as mass flow mixed with water that enters the root system in the transpiration flow. Little is known about how the plant regulates N influx or the relative importance of the two processes as N content varies. The two dimensional water and solute transport model 2DSOIL was modified to simulate active and passive transport. Measured data were from a N experiment with potato in sunlit controlled environment chambers. Six N levels from 2 to 14 mmol per liter N were applied. The experimental data showed that N uptake varied with carbon assimilation rate and the mean carbon to nitrogen ratio (C/N) of the plant. Total measured N uptake varied from 20 to 90 mg N per plant per day during the exponential growth period. Furthermore, passive N uptake was a small component of total N uptake but increased as N concentration in the soil increased. The simulated data showed similar relationships. These results suggest that active uptake is an important component of total N uptake and that the C/N ratio and carbon assimilation rates can be used to estimate N demand.