Description and calibration of a dynamic model for lettuce grown in a nitrate-limiting environment

-A three-compartment lettuce model designed to predict growth and nitrate concentration under severe nitrogen stress conditions is described and calibrated using data of N-limitation experiments. Since the limited amount of data does not allow calibration of all the model parameters, sensitivity analysis was used to determine which parameters should be estimated using this data. The calibrated model predicts quite well the main observations associated with severe nitrogen stress: reduced growth, fast depletion of nitrate, gradual reduction of reduced-N content, and considerable increase of dry matter content. After being deprived of nitrate for 21 days, stressed plants are five to ten times smaller than unstressed plants, and their dry matter content is two to three times higher than normal. Nitrate concentration of N-stressed plants drops to an insignificant level within three days, while reduced-N content decreases steadily throughout the experiment. All these observations are correctly predicted by the model. (~) 2004 Elsevier Ltd. All rights reserved. Keywords--Excess carbon, Lactuca sativa L., Nicolet, Nitrogen stress, Sensitivity analysis. N O M E N C L A T U R E bg bp Cjj light extinction coefficient; unit: m2[ground]/mol[C] growth inhibition border photosynthesis inhibition border concentration of constituent J in compartment j ; unit: mol[J]/m 3 exponent in respiration equation; unit: 1/K md