Field drying experiments were carried out during the 1975 through 1978 harvest seasons at the University of Minnesota Rosemount Experiment Station. Several combination drying experiments were conducted each season along with a control (conventional drying) experiment. Based on the results of the field experiments, comparisons of energy requirements for combination and conventional drying were made. Performance of the low-temperature, in-storage phase of combination drying was evaluated using computer simulation. Drying performance using ambient air was compared to performance when small amounts of supplemental heat were added, either solar or constant source heat. Long term weather records were used to evaluate variations in performance from year to year.