Leaves are full of minerals and once they are added to the garden they feed earthworms and other microbes. They can also lighten heavy clay soils and help to retain moisture in lighter sandy soils.
The benefits of a garden mulched like this are the reduction of soil erosion, less weeds to compete for nutrients, and better water retention. Most other soil amendments can simply be placed on top or gently raked into the wood chips.
Your kitchen is a gold mine for improving your soil quality! Your morning coffee grounds. Your daily banana peel. All those egg shells! All of these things will add something different to you soil in terms of nutrients.
Coffee grounds, when mixed into the soil or compost, will improve your soil structure, tilth, and even help to repel certain pests. The grounds are high in nitrogen, which is great for those heavy feeders in your garden.
Manure from all sorts of animals can be added to your garden beds and fill it with nutrients to help improve your garden soil and feed your plants.