Zaï holes are holes dug in the soil. They also catch water, but in a different way. They used to only be used a little bit to make land better for growing plants. Yacouba Sawadogo had the idea to fill the holes with manure and other things to make food for the plants. The manure attracts termites, whose tunnels help break up the soil even more. He also made the holes slightly bigger than the traditional ones. Zaï holes have been used to help cultivate trees, and crops like sorghum and millet.