Most people have heard that loam soil or loamy soil is the best for gardening, but that leaves the question: what is loam soil and what makes it so good?
The simple answer is that loam soil has all the components that make up soil in the ideal ratios. Because loam soil is so well balanced, it has a lot of attributes that plants need to thrive. But is loamy soil the best choice for every plant? And how can you tell if your soil is loamy?
Loam soil is an ideal balance between soil that holds on to too much water and soil that drains too quickly. Dense soils with a lot of clay hold onto water, and this can lead to root rot in plants. This type of soil is also pretty firm, making it difficult for your plant to spread its roots.
On the other hand, loose, sandy soil doesn't hold on to enough water and dries out too quickly for many plants. Loam soil is somewhere in between, soaking up enough water to support healthy plants but draining well enough to prevent the roots from sitting in too much water.
Loam soil is friable, meaning its texture supports the underground activity plants need for healthy growth. Specifically, its crumbly texture lets plants spread and grow a robust root system.
This support benefits all plants, but it's especially helpful if you're growing root vegetables, like potatoes and carrots. Loam soil allows these edible roots and tubers space to grow.
All soil has the same components: sand, silt, and clay. Sand is large, irregularly shaped particles that don't fit together easily, which is why water drains through sand so quickly. Silt particles are similar but smaller, so silt doesn't allow water to drain quite as much as sand does.
Clay has tiny particles that stick together. Although the spaces between the particles are small, clay has a lot of surface area and holds a lot of water. Clay also breaks down over time into elements like iron, aluminum, silicon, and calcium and may crystallize. It shrinks when it's dry, so in periods of drought, wide cracks often form.
Loamy soil is a mix of all three components, roughly made up of equal parts silt and sand and half as much clay.
Good loam soil needs all three of these components—sand, silt, and clay—because each one does something for your plants. Sand allows for good drainage and aeration, while clay is higher in nutrients than the other components. Silt is somewhere in the middle and helps the sand and clay mix together more easily.
One way to tell if you have loamy soil is by feel, though this may take some practice. Pick up a handful of damp soil and squeeze it into a ball. Then, open your hand and watch what happens.
If the soil immediately collapses, doesn't hold its shape, and sifts through your fingers, it's sandy. Silty soil will stick together but flatten as you open up your hand and eventually crumble as it dries, while clay soil maintains its shape and hardens as it dries. Loam soil will form a ball, but if you press it, it will crumble.
Another way to tell what kind of soil you have is the jar method, but this takes some time and preparation. Get a glass jar with a lid and fill it halfway with your soil. Then, add water until the jar is 3/4 full. Put the lid on tight, then shake the jar to mix everything. Set it aside for about eight hours, then check the jar.
The soil should have separated into layers. Sand is the heaviest, so it sinks to the bottom. The silt will be in the middle and the clay at the top. Remember, you want one part sand (about 40%), one part silt (about 40%), and half a part clay (about 20%). If that's how the layers form in the jar, you have loam soil.
If you test your soil and discover it is more clay or sand than loam, you can correct it. Some people think you can just add sand to clay soil or clay to sandy soil, but clay and sand don't like to mix. Unless you add some organic matter, you will end up with soil that resembles cement.
Creating loam soil takes some time. You likely won't see improvement the first year, but it will get better in time. Maintaining loam soil is not difficult, but it is an ongoing process. Every year, plants use up the nutrients in the soil, so you have to keep replacing them.
There are many ways to add organic materials to your soil to make it loamy. After your crops have died in the fall, add a layer of compost, dead plants, or other organic material to the top of the soil and let it sit over the winter. Use a tiller to work the material into the ground in the spring, and repeat yearly.
You can also plant a cover crop, like clover or alfalfa, and till it into the soil before winter. Again, let it sit, then work it into the top six inches or so of the soil before planting in the spring.
Loamy soil is a good choice for many plants, including many popular large-scale crops like wheat, sugarcane, and cotton. It's also a good choice for many vegetables you might want to grow in your backyard garden, like peppers, green beans, lettuce, tomatoes, and cucumbers.
Many flowers, like snowdrops, daffodils, and grape hyacinths, also love loam soil.
In places that get a lot of rain, people often prefer sandy soil because it has better drainage, especially if they are growing things like potatoes or carrots that may rot if there's too much water in the ground.
Plants like succulents and cacti that store water also do better in sandy soil.