According to U.S. De­­part­ment of Agriculture statistics, 30 percent of the 3.3 million U.S. farm operators are women, and women are the principal operators of 14 percent of the nation’s farms. But it might be hard to tell that in photos representing farm life.

Marji Guyler-Alaniz of Urbandale has made it her mission to reflect the country’s female farmers through...