PHOENIX-Thirty miles south of Phoenix, Arizona, green fields of alfalfa and pima cotton stretch toward the sun producing triple-digit heat. Hundreds of yellow butterflies dance above the purple flowers that dapple the tops of the young alfalfa stalks-to expert eyes, the flowers signal that the plants are heat-stressed and should be harvested soon.
Gila River Farms near Sacaton-which is named after the Pima people who inhabited the Gila and Salt River valleys-has been growing alfalfa and high-end cotton for 50 years. That seems a long time but is merely a flash considering that the roots of Ari...