The image shows a potato harvest by apprentices at the UCSC Farm and Garden in 1990. Due to the use of copious amounts of compost, the potato beds yielded about one pound of potatoes per square foot, or about 1000 pounds total from these four beds, each 80 feet long. Others actually do their composting in the soil, by burying kitchen wastes and other materials in trenches in the garden. It is also fine to top-dress houseplants occasionally with small handfuls of finished compost. This is essentially the same as a 'top dressing' application, described above, but mulches are typically meant to cover all of the soil around the plants that get mulched.
Mulches protect the soil from erosion.
The also save water by shielding soil from the drying effect of the wind and sun. As they decompose, mulches add nutrients to the soil, and if composed of small-enough particles, worms may slowly eat the mulch and incorporate it into the soil. Compost tea is made by combining equal parts of compost and water and letting it sit for a while. When you're finished making compost tea, use the mucky dregs as a mulch in the garden or landscape. Compost does several things to benefit the soil that synthetic fertilizers cannot do.