There is no one source. It’s mentioned in several SBC Alumnae Magazines (with photos). Jan Osinga, the former dairy manager, wrote a book where he organized his recollections of the Dairy. The bookstore should have a copy of it. I think it’s called “My Story” or “The Best Years of My Life.”
I don’t have any published articles or references on hand. But if you read through Elijah Fletcher’s letter (edited into a volume, available in the library) you can read about the 19thC orchards. By the 1950s the College had phased out all of the orchards.