[2] Caldwell was a member of the American Phytopathological Society, where he served as President of the North Central Division and Treasurer.

They organized a three-crop per year rotation with two crops in the greenhouse and one in the field, including fall planting of grains such as winter wheat, barley, and oats.

As department head, Caldwell also supported programs to study soybean diseases, apple scab resistance, and the impact of the cereal leaf beetle.

[1] Caldwell encouraged open an exchange of information and plant materials from the Purdue program, widely sharing its breeding stocks.

He brought scientists together from the fields of plant pathology, agronomy, and entomology and created an infrastructure for interagency collaboration between Purdue and the USDA.

[1] Caldwell developed disease-resistant cultivars for a wide variety of plants, including small grains, corn, soybeans, tomatoes, and apples.

[1] Cultivars such as Triticum aestivum L. 'Caldwell', released by Purdue in 1981, continue to be used to study the genetic basis of disease resistance to leaf rust caused by Puccinia triticina.