Jon I. Lizaso, Agronomy, University of Florida, PO Box 110500, Gainesville, FL 32611, Kenneth Boote, Agronomy Dept., 304 Newell Hall, University of Florida, University of Florida, PO Box 110500, Gainesville, FL 32611-0500, James Jones, University of Florida, Agricultural and Biological Engineering Dept, PO Box 110570, Gainesville, FL 32611-0570, and John Lindquist, PO Box 830915, University of Nebraska-Lincoln, University of Nebraska-Lincoln, Department of Agronomy, Lincoln, NE 68583-0915.
In previous work, we developed a maize (Zea mays L.) leaf area simulation model calculating expansion and senescence on a per-leaf basis. We also developed a layered leaf-to-canopy photosynthesis and respiration model calculating the daily assimilate contributions of each leaf. To continue model development we wanted to simulate nitrogen dynamics on a per-leaf basis and to link N and photosynthesis processes. In the present work we linked the daily allocation of carbon resources with leaf area expansion and senescence processes for each individual leaf. We also modified N uptake and allocation, partitioning N to individual leaves. A new in-house maize model was used adapting code from the CSM-CERES distributed with DSSAT 4.0. Specific leaf area (SLA) per-leaf was calculated considering the effects of irradiance and temperature. Individual leaf demand for assimilates in growing leaves was then obtained by dividing the leaf area growth rate by the specific leaf area. When the daily supply of assimilates is not enough to provide the potential demand of organs, carbon allocation is limited to the actual supply and leaf expansion is reduced to maintain the calculated SLA. A maximum N uptake calculated as a fraction of daily assimilation was introduced. Plant N was partitioned among roots, stems, leaves, ears, and grain. N dynamics in individual leaves was linked to leaf area expansion and senescence. The model was tested using field measurements of individual leaves in experiments where population densities were varied in the range 7-22 plant m-2. The N allocation was evaluated using data from 3 years and 3 population densities within the range 7-11 plant m-2. Our results showed reasonable accuracy when the simulated leaf area, leaf dry weight, and leaf N were compared against individual leaves and against whole canopies.
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