Peter Mwete, an angular Zimbabwean man in his 20s, was weeding his tiny vegetable plot in the settlement of Marimari when I met him in 2002. The 100-square-meter plot--about the size of a typical suburban backyard--was enclosed by a two-meter-high fence of stout poles cut from the bush and wired together to keep wild and domestic animals out. Peter lived with his father and a 19-year-old brother; his mother had died from AIDS, and his brother was also dying. To feed his family and earn a living with fewer hands to do the work, Peter had installed a low-cost, gravity-fed drip-irrigation kit provided by International Development Enterprises (IDE), the organization I started in 1981.

Peter's plot consisted of eight raised beds neatly planted with rape leaves, cabbage and corn. In the middle of each bed, a movable drip line delivered water from a 40-liter plastic tank placed atop a wooden stand. Because the drip system brought water directly to the roots, it was far more efficient than watering the plants by bucket. As a result, the small plot produced enough corn and vegetables to meet most of the family's needs, and Peter expected to earn at least $90--a substantial income for a farmer in Zimbabwe--from selling the surplus. He told me that in the following year he planned to double the size of his plot and triple his income by replacing some of the leafy vegetables with more valuable crops, such as tomatoes and Irish potatoes. He also planned to raise his plot's productivity by fertilizing it. Because he could not afford chemical fertilizers, he intended to dunk a burlap bag filled with cow manure into a water drum and apply this "manure tea" to the roots of his vegetables through the drip system.