There are only a few basic soil types, all of which are a combination of three ingredients: sand, silt and clay. The mixture is called a “loam,” which is ideal for plant growth.
The combination determines how soil feels and holds water. As well as how it must be worked and which plants will grow well.
Soil tends to favor one material over the other two. Loamy sand, for example, is about 40 percent sand, 40 percent silt and 20 percent clay. It’s good for root vegetables such as carrots and beets. Plus leafy vegetables and tomatoes.
Let’s take a look at each of the main soil types. They are identified by the majority of mineral elements found in them.
Clay soil is fertile but needs preparation structurally. It is composed of tiny mineral particles. They reduce the air space in the soil This causes it to retain water and become easily compacted.
When wet, it becomes packed, poorly aerated and difficult to work. When dry, it can crack. And that damages roots, sometimes forcing plants from the soil.
Clay soil and the water within are cold. So, they need time to warm up in the spring. This delays planting schedules. In summer, it can turn hard, compact and difficult to turn.
You can turn clay soil into a looser, crumblier medium by mixing in large amounts of organic matter. This stabilizes the topsoil and reduces crusting. It also improves drainage, retains nutrients and lessens runoff. Once good soil structure is achieved, it won’t need annual amending like a sandy soil.
Green composting materials that rot quickly, such as young leaves, work well. Organic fertilizers can improve soil structure. Such as blood meal, kelp extracts, cottonseed meal and fish emulsion. The best time to till is in autumn. That’s when clay is at the right moisture level for handling.
Drip irrigation works best with clay soil. It delivers water slowly to soak roots and drain away. Use a soaker hose trickling a cup of water per minute across garden beds for one to three weeks. This will distribute water evenly, reducing bare spots.
Here are a few plants that take naturally to clay soil:
- Edibles: cabbage, bean varieties, broccoli, cauliflower; plus yarrow, red valerian, barberry, currant and dwarf quince
- Trees: coffee, balsam fir, box elder, blue beech, hawthorn, ginkgo biloba, butternut, apple, crabapple, pear, willow, oak, aspen, cottonwood, elm, cherry, maple and black walnut
- Shrubs: lilac, honeysuckle, juniper, witch hazel, potentilla, Russian olive and burning bush
- Flowers: aster, black-eyed Susan, coreopsis, daylily and Japanese iris
- Ornamental grasses: Canadian wild rye, switch grass, Indian grass, fountain grass, and prairie cord grass
Silty soil is a close second to loam, the gold standard of gardening.
The small, irregular-shaped soil particles allow for good aeration. Silt holds water like clay soil but also drains well. It stores nutrients well because it is compactable. Silty soils have a weak structure. They are easily broken up and worked in a garden.
Silty soil is often a native to river valleys. A garden near a river or what was once a riverbed may be this soil type. Silty soil can compress and become saturated. Air can’t circulate. This drowns roots and prevents absorption of nutrients.
Amend silty soil annually with an inch of organic matter like compost. Or thoroughly decayed sawdust or wood shavings. Add organic fertilizers when needed and cover the soil with two to three inches of mulch. Periodically turn over several inches of the top layer of the soil. That will keep it crumbly and easily worked.
Minimize walking on garden beds to prevent compacting the soil. Build a walkway of narrow boards between plots, especially in vegetable gardens. That will reduce stepping on the soil. Water when a pinch of topsoil is dry to the touch. Give the soil time to dry between waterings so roots dig deeper into the soil.
Plants that love silty soil include:
- Crops: beets, lettuce, onions, garlic, cabbage, carrots, turnips, parsnip and many other cruciferous and root vegetables; plus strawberries, raspberries, blackberries, citrus trees and pomegranate trees.
- Trees and shrubs: weeping willow, bald cypress, red twig dogwood, river birch, red chokeberry, and American elder
- Flowers: yellow iris, Japanese iris and swamp milkweed.
Sandy soil is light to work and warms quickly in the spring. It has the largest particles – up to 1,000 times bigger than clay. And it drains freely because of air spaces between them.
Sandy soil feels light and gritty. It cannot be molded into a shape. It dries easily and fertility is low as nutrients simply wash away.
Water drains rapidly out of the reach of seedlings. Annually adding organic matter such as compost or peat will help the soil retain water. And it will add nutrients to sustain healthy plants.
Till and turn over plants such as clover, vetch, oats, young weeds and nettles of any kind. Also consider peat moss, compost and old sawdust. Or sod, straw, native peat and other garden refuse.
Mulch helps the soil retain water during hot, dry seasons. Apply mulch after transplanting and when plants are already growing. Apply to a two-inch depth annually in late autumn for perennials and shrubs.
Water plants frequently at shorter intervals. Soaker hoses and drip irrigation systems work well. For water-hungry plants like tomatoes, consider burying pine logs about three feet deep. The decaying wood slows drainage and adds nutrients to the soil.
Sand-tolerant plants include:
- Root vegetables and leafy greens: Carrots, lettuce, potatoes, turnips, parsnips, collard greens, strawberries, zucchini, squash, peppers
- Herbs: Bush clover, bayberry, creeping juniper and thyme
- Other plants: artemisia, euphorbia, oregano, perennial flax, Russian sage, Rosemary, thyme, lavender and tulip
- Trees: Eastern white pine, red cedars, pomegranate and fig trees
- Shrubs: Japanese barberry, Siberian pea shrub, flowering quince, gray dogwood, common smoke tree, privets, bayberry, bush clover and red chokeberry
- Ornamental vines: trumpet vine, Oriental and American bittersweet, winter creeper, trumpet and Hall’s Japanese honeysuckle, and hardy grapes
- Blooms: blanket flower, California poppy, cleome, crape myrtle and lavender.
If after reading the information above you’re still not sure what type of soil you have, try this test.
Dig into the ground about six inches deep and fill a mason jar with it. Pour as much water into the jar as you can, replace the cover and shake well.
The mixture will settle and you’ll see layers of the composition of your soil type. Clay will stay at the top, sand will sink to the bottom and silt will sit in the middle.
Another option is using a soil testing kit, but you’ll have to mail it back to the company that made it to get your answer.
In addition to determining what type of soil you’re working with, you should learn its pH level. That will help you decide which plants to grow. The pH level is a measure of the soil’s acidity or alkalinity. It ranges from 1 to 14.
Most plants grow best in soil with a pH level between 5.8 and 6.8. You can identify your soil’s pH level with a testing kit.
For this test, use small samples of soil from various areas of your garden or vegetable plot. Don’t take samples from waterlogged areas.
Place each sample in a separate polythene bag and label it by where in the garden it was taken. Allow each sample to dry out before following the kit instructions.
No matter what kind of soil you have, you can plant, nurture and harvest food for you and your family. So, get out there and get growing!