If you’re at all familiar with gardening you know at least a little bit about loam soil. It seems almost to be the holy grail of gardening. Gardeners swear by it and spend thousands of dollars and years of their time to build good, loamy soil.
If you’re not convinced that soil can spell the difference between success and failure in the garden, keep reading about the miracle soil we call loam.
So what is loam? Loam soil is a mixture of clay, sand, and silt. It has high fertility, good drainage, and moisture retention. It provides excellent aeration and has good workability, perfect for healthy root growth.
If you’re lucky enough to have natural loam soil the work doesn’t end there, but your job is going to be easier than the gardener who isn’t blessed with loam. Luckily, you can build loam soil over time by regularly applying organic compost to your beds and working it into the soil.
Keep reading to understand more about what loam soil is, how it compares to other types of soil, and how to build loam soil in your own garden.
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The different types of soil
There are six major types of soil: loam, silt, clay, sand, peat, and chalk. Each sediment behaves a little bit differently, and each type has its benefits and disadvantages as a growing medium.
Sand
Sand is the largest soil particle, and although sand has excellent aeration and good drainage, it doesn’t contain much nutritional value.
When you do fertilize sandy souls, the nutrients are prone to wash away because sand is so well-draining. Fortunately, sand is easy to cultivate and is among the first soils to warm up in the spring.
Clay
Clay holds water almost too well, and it is rich in minerals and nutrients that plants need. However, clay’s minuscule particles compact very easily, heavily reducing the soil’s capacity for drainage and aeration.
Clay is hard to work and tends to have an acidic pH, which is not ideal for plants.
Silt
Silt is in between sand and clay in terms of both the size of the particles and in nutritional value – silt contains more minerals than sand but less than clay.
Silt is helpful as a bonding agent – it blends sand and clay together in such a way that the benefits of both types are highlighted while the feature the benefits of each while the disadvantages are masked.
Peat
Peat is a porous, spongy soil type with great aeration. Peat soil is very acidic, so you’ll want to amend peat soil with an alkaline substance like lime to neutralize the pH.
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Peat soil isn’t particularly nutritious, so fertilizing is a must.
Chalk
Chalk soil is composed of calcium carbonate and is often very alkaline. Chalk soil is very rocky, making it a difficult growing medium to till or cultivate.
Chalk does have excellent drainage and a is fairly nutritious, but its chunky texture only works as a growing medium for very shallow-rooted plants.
Loam
Loam soil is relatively equal mixture of sand, silt, and clay – it’s the fertile, crumbly soil we all wish we had in our gardens!
According to a report backed by the the University of California’s Agriculture and natural Resources Program, loam soil is roughly 40% sand, 40% silt, and 20% clay.
With these proportions, loam retains the good characteristics of the other soil types without the disadvantages of each, making it ideal for growing just about anything.
When these three cohesive soil types are combined, a crumbly, airy, nutrient-rich medium. Loam soil’s porous texture allows for the perfect exchange of oxygen and water between plant roots.
Loam has good aeration and moisture retention, excellent drainage, and good workability. It’s nutrient-rich composition makes loam a coveted growing medium.
| Soil Type | Traits |
|---|---|
| Sand | Large particles Good aeration Fast drainage Low nutrition Can get too dry |
| Clay | Small particles Low aeration Slow drainage Good nutrition Stays wet Acidic pH |
| Silt | Medium particles Medium aeration Medium drainage Medium nutrition |
| Peat | Porous Spongy Good aeration Low nutrition Very acidic |
| Chalk | Rocky Hard to till Medium nutrition Alkaline pH |
| Loam | Sand/silt/clay mix Good aeration Good drainage Good nutrition |
of each of the 6 basic soil types.
Characteristics of loam soil
In comparison to other soils, loam is widely regarded as the ideal soil for plant growth. Light soil, consisting of mostly sand and silt, is not as nutritious and doesn’t retain moisture.
Clay soils are heavier than loam, have poor aeration, and often require a lot of conditioning to become a decent growing medium.
Loam is much better for gardening projects than clay or sand, or silt soil alone. When compared to peat and chalk soils, loam is the obvious winner for its desirable characteristics.
Loam is much easier to work with, has better drainage and aeration, and usually has a neutral pH. It’s also much more fertile, because of its clay and silt makeup.
In an article published on Purdue University’s Yard and Garden News, Rosie Lerner defines loam as a soil that
“combines all three of these types of particles [sand, silt, and clay] in relatively equal amounts.”
https://www.purdue.edu/hla/sites/yardandgarden/what-is-loam/
She goes on to make the claim that
“Loamy soil is ideal for most garden plants because it holds plenty of moisture but also drains well so that sufficient air can reach the roots.”
https://www.purdue.edu/hla/sites/yardandgarden/what-is-loam/
Loam soil is ideal for most crops because it retains water, but is at the same time a well-draining growing medium.
Loam allows for an adequate exchange of air and water between soil particles and plant roots.
Loam is a nutritious growing medium due to its clay and silt composition. Loam tends to retain nutrients better than other types of soils, so when you fertilize the garden the nutrients remain right where the plants need them.
Loam soil is often described as “friable,” or crumbly, in texture. Loam soil is characterized as being relatively uniform in texture, without major clumps.
It is important to note that the qualities of loam soil vary depending on the plant species and geographic area. The ideal ingredients for loam soil can vary from one area to the next.
For instance, loam soil in a wet area may contain more clay than loam soil in a dry area.
Loam is the perfect soil for most annual flowers and vegetables. It’s heavy enough to anchor tall plants like sunflowers and tomatoes, but it’s also light enough to allow for healthy growth of root crops like carrots and beets.
Of course, loam is an excellent growing medium for perennials, too! Perennials and herbs tend to be a bit more forgiving of poor soils, and some fruits like blueberries and strawberries prefer acidic soil, so even loam may need to be amended to suit specific crop needs.
But as far as the typical garden goes, it doesn’t get better than loam.
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Disadvantages of loam soil
The main disadvantage of loam is that it can quickly become water-logged and can even become anaerobic in certain conditions. After heavy rains or irrigation, loam may require tilling, loosening, and additional drainage structures to allow excess water to escape.
Compacting and crusting can occur, so it is important to keep an eye out for these things and remedy them as soon as possible. For more information about preventing soil compaction, check out this article.
Loam may also become over-saturated with water which can lead to root rot. Take care not to over water your garden to prevent the onset of soil-borne fungal diseases.
Where is loam soil found?
To find out the soil makeup of your area (and to see if you already have loam soil) check out the USDA Web Soil Survery.
Click on the green “Start WSS” button and use the “Quick Navigation” column on the next page to search for your garden by address. You can also double-click the map to zoom in until you find your property.
Once you’ve located your property, you’ll notice several buttons in the map legend. Choose either of the ADI button (one draws rectangles and the other draws freehand shapes), and outline your garden.
At the top of the page, click on the “Soil Map” tab to reveal your garden’s native soil, according to the USDA study.
Do a soil test to find out if you have loam soil
Find out how much of your native soil is loam by doing a ball test.
First, pick up a handful of native soil and make a fist with your hand. Release your fist and notice how the soil reacts.
Does it hold its shape, even when you move your hand? If so you have clay soil.
Does the soil never form a ball? You likely have sandy soil.
If your soil ball holds its shape for a moment or two before crumbling, congratulations! You have loam soil.
You can also contact your local extension office for instructions on how to do your own soil test at home. Usually you will dig up a sample from a few different places in your garden, and then ship the sample to whichever lab your extension office recommends.
How to make loam soil
If you don’t already have loam soil, don’t fret – you can make your own, but it isn’t a quick process. It may take some time and effort to get the right mix but with patience, you can create your own loam soil. And it doesn’t involve mixing sand, silt, and clay together in a wheelbarrow.
The best way to create loam is by building good soil. The best way to build good soil is by amending your garden beds with organic compost at the beginning of each growing season.
Compost contains valuable nutrients and hardworking microorganisms that will break down the organic matter into a nutrient-rich humus, also called loam.
Use your own compost, if you have some, and if not (or as a supplement) you can buy nutrient-rich compost. Check with area farmers or with your local garden supply store for organic compost or manure.
- Add nutrient-rich compost – Apply least two inches of compost to you garden beds at least once a year. If you have extra compost, amend the garden beds more often. You can add more compost every time you rotate crops.
- Add organic mulches – Throughout the season add organic mulches like straw and shredded leaves, which will eventually decompose and become loam. These organic mulches control the spread of weeds, as well as add nutrients and texture to your soil. As the seasons go by, you’re likely to notice a more fluffy texture in your garden, and the soil itself make take on a darker, richer color.
- Cultivate the soil by hand – Speed up the decomposition process by working your soil with a broad fork to a depth of six or seven inches at the beginning of the growing season. This will help to aerate the soil, break up any compaction, and help protect the soil from losing nutrients with the onset of winter weather.
Whatever you do, avoid mixing sand into directly into your native clay soil — that won’t have the same effect as it would in already loamy soil. Sand and clay form a material akin to concrete, and one that won’t be easy to remedy.
Amending your native soil with compost and silt is the easiest way to ease into loam soil. A single application of compost will not transform your soil to loam overnight, but it will certainly improve it.
You may never have perfectly equal proportions, but the more organic matter you add, the better off your native soil will be.
Conclusion
As a general rule, loam is the best type of soil for a garden because of its balanced and supportive environment for plant growth. To get soil that is as close to a “perfect loam” as possible, it is important to understand what kind of soil you have and to add amendments accordingly.
You can learn about some of the best plants to grow in poor soil here.
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Resources
Web Soil Survey – Home, https://websoilsurvey.nrcs.usda.gov/app/HomePage.htm. Accessed 11 January 2023.
Lerner, Rosie. “What is Loam? – Indiana Yard and Garden – Purdue Consumer HorticulturePurdue University Indiana Yard and Garden – Purdue Consumer Horticulture.” Purdue University, 6 January 2000, https://www.purdue.edu/hla/sites/yardandgarden/what-is-loam/. Accessed 11 January 2023.
Londeree, Nanette. “Garden Good Guys – Soil.” UC ANR, https://ucanr.edu/sites/MarinMG/files/116762.pdf. Accessed 11 January 2023.
About the author:
When not writing content or growing flowers in her native Virginia, you can find Sarah hiking a long-distance trail deep in the woods. Follow along with Sarah’s adventures at http://sarahcolliecreative.com.
