In central Spain, farmers practise the art of so-called dry farming. They have developed a method to grow crops in even very dry conditions. The fields are only cultivated during the winter season when rainfall is just enough to grow crops. Harvesting takes place just before the summer heat dries out the ground. After the harvest and before rainfall, the soil is roughly ploughed to maximize water absorption. It is then sealed with rollers to reduce evaporation. The fields are also surrounded by stone walls and organized in terraces to minimize erosion.