A Structured Procedure for Assessing How Crop Models Respond to Temperature

Abstract

Crop simulation models are widely used to analyze temperature effects on crop growth, development, and yield. Unfortunately, temperature responses of models often are not examined critically to ensure that a model is appropriate for a given research application. This paper describes a procedure for assessing how models respond to temperature. The procedure treats major processes in a balanced fashion but does not require access to source code. The results are easily interpretable by nonmodelers and readily documented and employed with different models. Sensitivity analyses are run using standardized conditions of nonlimiting water and N with regimes of constant mean temperatures from 3 to 40°C and daily range of 10°C. Daily model outputs define responses that are grouped in seven categories: crop mass (including economic yield), phenology, reproductive growth, canopy development, root growth, resource use efficiency, and water balance. To avoid interactions of duration of life cycle with growth, several responses are assessed before partitioning to reproductive growth reduces total aboveground biomass. Emphasis is on graphical analysis of individual variables vs. mean temperature, but cardinal temperatures and a response index are also estimated. When applied to the CSM‐CERES‐Sorghum and CSM‐CROPGRO‐Drybean models, the procedure readily identified differences in temperature adaptation of the two crops. Various examples were found where modeled responses appeared to differ from data from field or controlled‐environment studies. The proposed procedure will require adjustments for specific situation but provides a foundation for assessing modeled responses to temperature in a structured and reproducible fashion.