Soil
Soil has rock pieces made small by wind and rain and sun and snow.  The rocks are made of minerals and some of the minerals dissolve in water.  Some of the minerals dissolved in water can be used as food by plants. Soil also has dead and living things (organic matter) in it.  When a plant dies, it is eaten by animals including bacteria in the soil. When the bacteria are done eating, what is left behind is called humus. When the bacteria die the plant food (minerals) goes back into the soil.  A food for plants is called a "plant nutrient".  There are many kinds of plant nutrients.