While others in her Zimbabwean village agonize over a maize crop seemingly headed for failure, Jestina Nyamukunguvengu picks up a hoe and slices through the soil of her fields that are lush green with a pearl millet crop in the African country’s arid Rushinga district. “These crops don’t get affected by drought, they are quick to flower, and that’s the only way we can beat the drought,” the 59-year old said, smiling broadly. Millets, including sorghum, now take up over two hectares of her land — a patch where maize was once the crop of choice. Farmers like Nyamukunguvengu in...