In western Kenya, a Kellogg MBA is using ‘microequity’ to improve the lives of local farmers.

Andrew Youn was not happy about the passion fruit. The electric green ovules hung on the vine, each the size of a child’s fist. Not yet ripe, the fruits showed bumps and brown spots, suggesting they hadn’t been properly watered. They grew on vertical vines hanging off a larger stem strung about six feet above the ground. Some of the untrimmed leaves scraped the dirt, forming a staircase for soil-borne diseases. In a greenhouse a few kilometers away, 50,000 small plants awaited grafting and planting.

Youn visited several vineyards on a magnificent day in January, and the problems were always the same. He was good-natured but firm as he explained to farmers, through a translator, the need to trim the vines. One farmer, a woman in a headscarf standing on the red-brown soil, seemed to agree. Youn, a Yale University graduate from Minnesota, wasn’t intimidating. At 29, he’s skinny and wears T-shirts and sandals with socks. But in this corner of western Kenya people listen to him. He’s the guy who’s making them money.

A former consultant, Youn is the founder and head of One Acre Fund, a two-year-old nonprofit which aims to link the poorest farmers—those with one acre of land or less—to commercial markets. The concept of microfinance gained international attention in 2006 when its chief pioneer, Muhammad Yunus, won a Nobel Prize. It is practiced by a diverse group of organizations, ranging from huge banks to small NGOs such as One Acre. Each has its own approach but believes, at bottom, that providing capital to the world’s poorest people will create millions of new entrepreneurs.