Wellsprings of Wisdom, by C.R. Gibson
An ambitious farmer, unhappy about the yield of his crops, heard of a highly recommended new seed corn. He bought some and produced a crop that was so abundant his astonished neighbors asked him to sell them a portion of the new seed. But the farmer, afraid that he would lose a profitable competitive advantage, refused.
The second year the new seed did not produce as good a crop, and when the third-year crop was still worse it dawned upon the farmer that his prize corn was being pollinated by the inferior grade of corn from his neighbors' fields.