Phenology has guided agricultural decision making since the earliest days of farming. There is the American Indian folklore that one does not plant corn until oak leaves are the size of a squirrel’s ear. Phenology became quantitatively tied to agricultural decision making with the advent of “degree day” calculations more than two hundred years ago. Farmers in these earlier times understood that the start of a growing season was dependent on the accumulated heat from late winter into the early spring and not on calendar days. This accumulated heat could be quantified into degree days by analyzing temperature measurements. The accumulation of degree days could be correlated with crop development or its phenology, either from the time of planting or emergence as in the case of annuals or from the time of bud break as in the case of perennials. The use of accumulated degree days was thought of as “biological” calendar for tracking crop phenology. While degree days still remain by far the most popular method of analysis for crop phenology, other factors began to be accounted for with the advent of computer models in the second half of the twentieth century. Crop phenology models not only became more sophisticated in the simulation of life stages, but they began to play a central role in agricultural decision making. This was especially true of crop phenology predictions that used weather forecasts as input. Growers today can now anticipate the future development of a crop and plan management practices accordingly.

Results/Conclusions

This presentation provides examples of how crop phenology is used today in agricultural decision making. These examples range from a user interacting with an irrigation schedule in a specific field to public, geo-referenced maps, which show crop development patterns over a large geography. With each example, one will appreciate the critical role crop phenology plays in agricultural decision making.