The time available for the completion of field operations, commonly referred to as field days, is important to the economic efficiency of crop farms. The effects of field days on economical cropping decisions is complicated by the significant variation which occurs in field days from season to season and year to year. This paper discusses the use of field days data in economic models of crop farms. It presents two linear programming models of a midwestern U.S. corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] farm. The first model treats field days deterministically, with known values in each production period. The second model treats field days as random variables, using the technique of discrete stochastic programming. Optimal solutions from the two models are compared to demonstrate the economic impacts of field days variability [...]