Throughout a plants life cycle, nutrients from the soil are used to sustain the plant. Before Agriculture, most plants would grow and die. The dead materials from the plant would eventually decompose and become soil. Which other plants would then use and the cycle would then continue. In the present day plants are harvested (specifically vegetable crops) and the nutrients in the plant will never become part of the soil again. Composting organic materials is like recreating the natural occurrence of decomposition making new soil, that is rich in nutrients which plants can again use. A huge advantage compost has over commercial fertilizers is that commercial fertilizers have a tendency to leach out of the soil becoming unavailable to the plant. Compost is highly stable so it maintains its chemical composition. Nutrients are only released when the plants need them so it is naturally a slow release fertilizer.
Here are some organic gardens
