Soil building refers to the process of improving and maintaining the quality, health, and fertility of soil through various methods. This can include adding organic matter such as compost or manure, using cover crops to prevent erosion and add nutrients, reducing tillage practices to avoid disturbing the soil structure, and implementing crop rotation techniques to maintain soil fertility. The goal of soil building is to create a sustainable and productive environment for plants to grow, while also preserving the health of the soil ecosystem.