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Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/8/2006 Publication Date: 10/3/2006 Citation: Fleisher, D.H., Timlin, D.J. 2006. Modeling expansion of individual leaves in the potato canopy. Agricultural and Forest Meteorology. 139:84-93. Interpretive Summary: Crop growth models are used to predict plant responses to environmental factors including light and temperature. Scientists and farmers can use these predictions to help make decisions such as when to irrigate or add fertilizer. Crop models for potato use a simple approach to simulate the growth and development of leaves and stems. The accuracy of these models can be improved by adding more detail on potato canopy growth. Experiments were conducted to evaluate the pattern in which potato leaves expand in the canopy as a function of temperature and the carbon dioxide concentration in the atmosphere. A model was developed to simulate leaf growth from this data. The results indicate that the leaf growth simulations are accurate and can be used to improve existing potato models. The leaf growth routine has the potential to be adopted for other crops as well. Farmers, scientists, and policy planners who need improved predictions on potato responses to nutrient, water, climate, and land-use changes will benefit from the research. Technical Abstract: A model to simulate expansion of individual leaves in the potato (Solanum tuberosum cv. Kennebec) canopy was developed by modifying an existing growth model. Data for model development and testing were obtained from three soil-plant-atmosphere-research (SPAR) chamber experiments. The first experiment (D1) used six SPAR chambers with treatments of 14/10, 17/12, 20/15, 23/18, 28/23, or 34/29 degrees C day / night temperatures (16 hour thermoperiod) at an elevated atmospheric carbon dioxide concentration ([CO2]) of 740 ppm. Experiment D2 used two SPAR chambers at 23/18 degrees C at 740 ppm [CO2]. Experiment D3 duplicated the temperature treatments of D1 but at ambient [CO2] (370 ppm). Potato leaf area expansion was sensitive to air temperature, with maximum individual leaf area values increasing with decreasing temperature. Growth duration, defined as the time interval between leaf appearance and when 99 percent of final area was attained, was negatively correlated with increasing temperature. The shortest durations were observed at 34/29 degrees C. Temperature response and leaf aging functions were developed from D1 and used to modify the existing growth model. D2 and D3 data were used to evaluate the model simulations during conditions of non - limited and limited carbohydrate availability. By varying an input to the model that simulates the effect of plant carbohydrate status on leaf expansion, the model was shown to be capable of reproducing leaf growth curves within 8 percent of the measured final area. The leaf expansion model is suitable for integration with existing potato models that simulate canopy leaf appearance. The expansion model provides a mechanistic approach for coupling plant assimilate, water, and nutrient status with canopy expansion. The new response functions in the model can also be modified for use in different crop models. |
