Crop simulation models require a minimum set of data in order to be able to provide a reliable and accurate simulation. Different crop models developed by different modeling groups might have slightly different requirements, depending on the internal science of the model or the overall goal and objectives of the model. However, in general crop simulation models require daily weather data, soil surface and soil profile information, and crop management data as input. Genetic information is in most cases also required, but might have to be calibrated based on local knowledged and observations. For crop model calibration and evaluation, additional data are required from either field experiments growth chamber and greenhouse studies, variety trials, or farmers’ fields. These could include yield and yield components, flowering and maturity dates, leaf area index, leaf number and vegetative growth stages, and other detailed observations, such as soil moisture, soil nitrogen concentration, etc. Many of these observations and measurements will depend on the goal and objectives of a particular application or modeling study. For instance, for an irrigation study one might be interested in determining the accuracy of the soil water balance simulation, while for a nitrogen fertilizer study one might be more interested in the accuracy of leaf, stem, or grain nitrogen and soil nitrate and ammonia concentration.

In order to prepare the data for model simulation, specific tools are required for those model users who not very familiar with crop models. In the DSSAT Software, there are tools for entering weather data (WeatherMan), soil data (SBuild), crop management (XBuild) and observational data (ATCreate). Specific tools for model calibration, especially for the genetic specific parameter or cultivar coefficients, are also provided.

Sometimes not all data are available to run a crop simulation models. Therefore, secondary data sources can be used, especially for spatial simulations. Common data sources used are the NASA Power data portal that contains daily weather data and the harmonized world soil database developed by ISRIC – World Soil Information.