Another method of enriching the soil is to dig down and fill the hole with layers of aged leaves and manure. Earthworms do most of the work of breaking down these materials into compost.
Build up the soil with compost or make your own organic fertilizer as recommended by garden writer Eliot Coleman: 4 parts blood meal, 2 parts bone meal and 1 part kelp or rock phosphate.
Here’s a good soil food recommended in the book Organic Gardening for the Pacific Northwest: 4 parts seed meal (or 2 parts fish meal), 1 part dolomitic limestone, 1 part rock phosphate or 1/2 part bone meal, 1 part kelp.
If you add bone and blood meal to coir, it will act as a fertilizer. Coir products are made from coconut fibre (from outer husk) and are used as an alternative to peat moss. Though I realize coir products have to be shipped long distances, that’s better than destroying peat bogs.
Leaf mould is an excellent amendment. Bag leaves and place them in a corner to break down, or dig them into a big hole and let them rot, or shred them and add to the compost heap. One thing you don’t do with leaves is throw them out.
Maple leaves tend to mat if you put them on the ground without letting them break down first. Since the leaves of Norway maples contain alkaloids, they should be well composted before you add them to the soil. Oak and beech are acidic and will take longer to break down than other leaves. But they are great if you are building up acid areas in your garden. Black walnut leaves contain juglone, which is toxic to many plants, so you should probably not use these leaves as soil amenders.
Extremely sandy soil is too porous and it won’t support earthworms. Add masses of compost and keep adding as often as possible. Over time the soil will improve.