Burning can be done quickly, in vast swaths of land, or more slowly with the slash-and-burn technique. Slash and burn agriculture entails cutting down a patch of trees, burning them and growing crops on the land. The ash from the burned trees provides some nourishment for the plants and the land is weed-free from the burning. When the soil becomes less nourishing and weeds begin to reappear over years of use, the farmers move on to a new patch of land and begin the process again.