How To: Build Soil
The creation of soil requires several things: a basic starting point, building blocks and correctives, and time. None of these things are negotiable, although all can be fudged based on your needs, your land, and your process.
The photo on the far left shows our original soil: compacted, acidic clay. It is not only wet, but water is pooling on the surface of the ground where it doesn’t have a way to drain. The other photos show a four-inch layer of wood chips going over the soil. The chips break down from the bottom up, enriching and loosening the soil bit by bit. As they are worked into the soil and disappear, I simply top them off with new.
1. The basic starting point — This is whatever soil you have right now. Bad, good, acidic, alkaline, chalk, sand or clay. Whatever you have, that’s where you begin. But what you have does determine your next steps. As an example, let’s say that you have acidic, clay soil (like me).
2. Building blocks — These are things that improve soil structure. In parts of my yard, I can dig up clay that is moldable and waterproof, the type of clay you make pots out of. The soil structure of clay is extremely tight. The particles of clay soil are small, and that allows them to slide and compress very easily. This is why clay is heavy and wet; it’s why clay holds water. In gardening, that means that clay soil won’t drain well … and that can lead to all kinds of problems, from fungal infections to root rot. This of it this way: if you can use your soil to make a bowl that will hold water without a leak, it does that exact same thing in the ground. You’re trying to grow plants in a bowl of water.
To improve the structure of heavy, wet, clay, I would want to introduce things that have a larger particle size. This breaks up the tiny particles of clay — thus making the soil looser and allowing drainage.
So, to my clay, I would add leaf mould (a fancy term for partially-decomposed fallen leaves) and woodchips. Both leaves and woodchips compost into the soil — leaf mould very rapidly — and help to break apart the clay. I could also add rock grit or sharp sand to my soil to help improve drainage, if I were so inclined, or if my soil weren’t also rocky. My soil is also rocky, so I don’t do this. Finally, I would add compost to my soil. Compost is the miracle drug of soil. It will do almost anything, including immediately improving soil structure. After all, compost is similar to soil itself. It doesn’t need to break down first; it will be rapidly incorporated into the soil by bugs, fungi and earthworms.
As a side note, you don’t need to dig up your soil to improve it. Some people do, and those people have more energy than I do. We’re also now learning that digging up the ground can actually disrupt soil creation. Most soil life (bugs, fungi, worms) are in the top few inches. By digging up and burying that soil life, we’re disrupting natural cycles. The better option is to simply layer mulches and other building blocks on top of the soil. Soil life will break it down for you, and this technique will result in the rapid creation of soil. That’s what we want.
3. Correctives — These are the things that improve soil composition or type. If I needed to correct my acidic soil, I might add mushroom compost or sulfur. If I had chalky, alkaline soil, I might add lots of compost and mulch with pine needles. Your soil may also be lacking in micronutrients, and even without a soil test, you can identify and correct simple deficiencies. Most deficiencies cause unique and notable issues for the plants growing in that spot. For instance, phosphorus deficiencies cause many plants to develop a purple tint in their stems or leaves, while boron deficiencies cause distinct brown spots on leaves and brown, soft, rotting cores in root crops and brassicas.
Common mineral deficiencies occur in nitrogen, phosphorus, potassium, magnesium, calcium, boron, and iron.
4. Time — Ah, time. This is the step over which you have least control. You can help time along, but soil still needs time to improve.
The main trick to speeding time is to intensively build and correct your soil. In other words, the more you add to your soil, the faster it will improve. The ten-inch layer of leaves and woodchips that I put onto my soil in 2020 had decomposed to four inches in 2021, and the tight clay of the soil beneath it had become darker and looser. I added another four inches of leaves in late 2021 and the soil continued to improve. In 2022, I’m going to do another 10-inch layer. After a few more years, this soil will be like similar soil I’ve been working for 5 years: rich, crumbly and so rich it’s black. The more I continue to enrich the soil, the deeper that richness will go.
The more you give your soil to work with, the more work it will do and the less time your soil will need to improve.
Although it seems counterintuitive, soil also improves when you grow things in it: whether that’s roses or grass or weeds or mushrooms. Grow whatever you can, keep amending and building your soil, and it will get better. I promise. The only soil that will never improve is soil you treat with chemicals.