Gardeners are often advised that a loamy garden soil is best for just about all plants. But just what is a loamy soil?
Soil is composed of many particles of varying sizes. Soil scientists have classified soil particles into three major groups: sand, silt and clay. Sand particles are the largest and tend to hold little water but allow good aeration. Clay particles are very small in size and tend to pack down so that water does not drain well and little or no air can penetrate. Silt particles are medium sized and have properties in between those of sand and clay.
A loamy soil, then, is one that combines all three of these types of particles in relatively equal amounts. 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.
Many gardeners complain of their garden soil being compacted and/or poorly drained. Heavy, compacted soil can be rescued by the enduring gardener. Add a good amount of organic matter, such as compost, animal manure, cover crops or organic mulch materials, each year as the soil is worked. It may take several years, but eventually the soil compaction will be improved. Although adding some sand along with the organic matter is acceptable, adding sand alone is not advised. The organic matter offers several advantages that sand does not, including increased water- and nutrient-holding capabilities, in addition to improved aeration.
Highly sandy soils can be a problem since they do not hold much water and few nutrients, as well. Adding organic materials to a sandy soil will improve its ability to hold water and nutrients. You’ll need to add at least a two-inch layer of material to make a marked improvement. This translates to about 17 cubic feet of organic matter to cover a 100-square-foot area.
And remember that soil improvement is a program, not just a one-shot deal. You’ll need to continue applications at least once a year for several years to really change the nature of the existing soil.
- All You Need to Know About Loamy Soil
- Soil Considerations
- Commercial Mixes
- Make Your Own
- DIY potting soil: 6 Homemade potting mix recipes for the home and garden
- What is potting soil?
- Potting soil ingredients
- Sphagnum peat moss:
- Coir fiber:
- Composted wood chips:
- How to make your own homemade potting soil
- General potting soil recipe for flowers, tropicals, and vegetables
- Potting soil recipe for potted trees and shrubs
- Potting soil recipe for succulents and cactus
- Potting soil recipe for seed starting
- Homemade potting soil for transplanting seedlings
- Potting soil recipe for houseplants
- What is soil?
- Inorganic component
- Organic component
- Further reading
- ARTICLE – What is Clay Loam
- TS1 – Premium sandy loam topsoil
All You Need to Know About Loamy Soil
While you may be concerned with watering or fertilizing during the growing season, are you giving your soil consideration? Loam—a particularly desirable combination of different soil components—is a top achiever in garden plots, capable of producing bumper crops and beautiful blooms.
Still, it’s not a set-and-forget solution that comes into play only at the start of the growing season. Most gardeners struggle with some type of soil issue—often an overabundance of clay or sand—and it’s an ongoing process to achieve and maintain a loamy soil. If you’re looking to improve the soil in your garden or flowerbeds, keep reading. We’ll dive into the importance of loamy soil and how you can get it in your garden by amending your soil.
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Types of soil are classified by the amount of sand, clay, and silt they contain. The composition of these different sized particles determines how well the soil will absorb and retain water. Each component brings something to mix, and loamy soil contains a mixture of all three.
• Sand particles are the largest of the three. While sand does not retain water, its large particles help to create spaces in the soil that permit air to circulate and bring vital oxygen to plant roots (also known as “aeration”).
• Clay particles are very fine, so they tend to pack tightly together, which leaves little room for aeration or drainage. Clay, however, is naturally nutrient-rich.
• Silt has medium-size particles—larger than those found in clay, but smaller than sand. This component is the most fertile of all three.
A BALANCING ACT
By blending all three soil components, loamy soil has the ability to retain enough moisture (as well as an abundance of nutrients) to keep plants healthy but also allow the excess to drain away. That balance is key to preventing standing water conditions, which can smother a plant’s roots. Indeed, loamy soil offers the best of all worlds, and its composition is agriculturally defined as being:
Less than 52 percent sand
Between 7 and 27 percent clay
Between 28 and 50 percent silt
Yes, it’s not an exact ratio. Since the percentages of the three main components can vary and still qualify the soil as loam, a gardener’s rule of thumb when trying to create the perfect loam is to strive for equal parts of sand and silt and half as much clay.
DETERMINING SOIL CONTENT
Achieving loamy soil can be a bit of a guessing game—you need to know what type of soil you currently have in order to know what you’re missing. One way to determine soil content is to collect a soil sample from your garden and take it to your County Extension Office (a branch of the USDA), for testing.
Many gardeners, however, learn to estimate the content of their soil by feel. To get an idea of your soil type, pick up a handful of slightly damp soil and squeeze it tightly in your fist to form a ball; then, open your hand and observe the results.
• Sandy soil will not hold a ball shape—it feels coarse to the touch, and it will sift through your fingers as you open your hand.
• Clay soil will form a firm ball that will retain its shape after you open your hand. If you set the ball aside and let it dry, it will become rock-hard and difficult to break.
• Silty soil will form a loose, slightly slimy ball that will flatten somewhat as you open your hand. If left to dry, the ball will become compact but it will break down into a powdery substance if crumbled between your fingers.
• Loamy soil forms a soft ball that will crumble if you press it with your finger. When dry, the ball will break apart easily.
A third method for determining the content of your soil is to fill a lidded glass jar halfway to the top with soil and then pour in water until the jar is three-quarters full. Put on the lid and shake the jar vigorously to thoroughly blend the mixture, and then set it aside. After six to 10 hours, check the jar—the soil and water will have separated and settled into layers. Sand (the heaviest) will be at the bottom, silt will be in the middle, and clay will be on top. If the sand and silt layers are relatively equal and the clay layer is about half their thickness, congratulations—you have loamy soil!
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Not as loamy as you’d like? If signs point imbalanced proportions of silt, clay, and sand, you can take steps to bring the soil into a more beneficial balance.
CREATING LOAMY SOIL
While it might seem as though you should be able to balance the components by adding sand to heavy clay soil or clay to sandy soil, it doesn’t work that way. Instead of achieving loam, you’ll end up with something akin to cement, which is very hard to dig and plant.
No matter what imbalance your soil currently has, the key to achieving a fertile loamy soil is to amend it with organic matter. This includes garden compost; peat moss; composted horse, goat, chicken, or cow manure; dried leaves or grass clippings; or shredded tree bark.
Creating optimal loam is an ongoing process—you’ll need to amend your soil annually because growing plants use up nutrients and water that runs off can also take nutrients with it. If your soil is heavy in clay or sand, you won’t fix it the first year—but you will improve it. It can take three to six years to obtain optimal loamy soil.
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Implement one or more of the following methods to get your soil in top shape, and keep it that way:
• Apply a two-inch layer of organic matter to the surface of your garden in late fall, after harvest is over and the plants have died. Wet the growing plot thoroughly until the organic matter is saturated, and then leave it in place to overwinter. In spring, work the soil well by turning it with a shovel or tilling it with a rototiller to a depth of six to eight inches. Repeat the process yearly.
• Plant a cover crop solely for the benefit of enriching the soil in the fall. Typical cover crops include annual ryegrass, alfalfa, sweet clover, and buckwheat; call your County Extension agent if you’re unsure which will grow well in your area. When the cover crop sprouts and reaches a height of three to six inches, till it under and then leave the growing plot undisturbed to overwinter. In spring, turn or till the soil to a depth of six to eight inches in preparation for planting.
• Mulch around plants during the summer growing season with a commercial mulch such as shredded hardwood bark, dry grass clippings, or dry leaves. Adding two to three inches of mulch will help keep the soil cool and moist during a hot summer and protect your plant’s roots while it’s decomposing. After harvest, turn or till the soil to work the now-decomposed mulch deeper into the soil.
• After annual flowers and vegetable plants die in the fall, pull them from the ground and lay them on top of the soil, wetting them down thoroughly. They will break down and decompose over the winter and can be worked into the soil in spring.
Soils vary in their properties and influence what crops will grow. Important soil characteristics include:
- Texture – the percent of sand, silt or clay particles that make up the soil, as depicted in the chart
- pH – acidity or alkalinity of the soil
- Fertility – nutrients available for crop growth
Select the best soil possible for high value specialty and agronomic crops; for hay or pasture, soil quality is slightly less critical.
Developing an understanding of the basics of soil physiology and the factors that affect plant fertility is essential for successful agricultural production.
What is Soil?
In addition to air, water, and nutrients, soils provide mechanical support to growing plants. There are four major components to soil: minerals, organic matter, water, and air. The approximate composition of a soil for optimum plant growth would have the solid space made up of 45% mineral and 5% organic matter, and the remainder would have roughly 25% water and 25% air. The water and air would be contained within the pore spaces of the soil.
Soil texture refers to the size of mineral particles, specifically the relative proportion of various size groups in a given soil. This property helps determine the nutrient-supplying ability of soil solids and the supply of water and air that support plant life.
Soil texture is divided into three parts—sand, silt and clay—based on particle size. Silt and clay soils impart a fine texture and slow water and air movement. They also have high water holding capacity due to the higher percentage of pore spaces. These are referred to as heavy soils, with clay being the heavier of the two. Clay is also the primary plant nutrient-holding mechanism in the soil.
Soil textural names are how we refer to and identify our soils. Sandy to gravelly soils are referred to as lighter soils, as water moves through more rapidly than the heavier soils, and they have lower water holding capacities. Sandy soils contain 70% or more sand by weight. Clay soils have at least 40% clay and may have names like sandy clay or silty clay. Loamy soils possess the desirable qualities of sand and clay without exhibiting the undesirable characteristics of extreme looseness, low water holding capacity and slow water and air movement. Some examples would be clay loam, sand loam, silt loam, and silty clay loam.
Soil pH is used as a measure of its relative alkalinity or acidity. Soil test results for pH are based on a pH scale where 7.0 is neutral, above 7.0 is alkaline and below 7.0 is acidic.
Soil pH is critical to health plant growth. It directly affects the availability of the essential nutrients to plants. It is important to know the optimum pH for the plants to be grown. Soil pH also affects the adaptability of plants in a given soil. Most agricultural plants prefer a slightly acidic pH of 6.4. However there are exceptions so be familiar with the pH and nutritional needs of all the crops to be grown.
The addition of any liming (alkalinizing) or acidifying materials should always be based on the results of a reliable soil test. Over-application of either can lead to crop injury.
Soil Organic Fraction
A good, loamy soil contains about one-half pore space (air and water) and one-half solid material. Of this one-half solid material, 90% is composed of minerals (bits of rock). The remaining 10% is the organic fraction. The influence of this small part of the soil on the soil’s ability to support plant growth is significant.
The soil’s organic fraction is dynamic and is always undergoing a process of change. The organic fraction consists of living organisms, plant and animal residues, and plant roots. Adequate levels benefit soil in many ways including; improved physical condition, increased water infiltration, improved soil tilth, decreased erosion losses, enhanced nutrient availability, and retention for plants.
Soil Compaction and Depth
Fine textured soils are more easily compacted than lighter soils, especially when they are wet. Compaction reduces pore spaces that hold air and water. Plant growth in compacted soils will be significantly reduced. Operating equipment on wet soils can create problems in a field for an entire season or longer.
Sometimes a soil is referred to as being deep or shallow. Soil depth can be defined as that depth of soil material favorable for plant root penetration. Deep, well-drained soils of desirable texture and structure are favorable for plant growth. Shallow, poorly drained soils are very restrictive to plant growth.
Soil Testing Services
Agro-One Services will test soil for nutrients and pH and indicate amounts of lime and fertilizer needed. Soil samples can be mailed, shipped via UPS, or taken to Dairy One’s sample pick-up points (see website), where you will fill out forms and pay for the testing. For more information, contact the lab:
Agro-One Agronomic Laboratory Services
http://dairyone.com/ or 800-496-3344
The Cornell Comprehensive Assessment of Soil Health offers soil testing services. They measure soil texture, available water capacity, field penetrometer resistance, wet aggregate stability, organic matter content, soil proteins, respiration, active carbon, and macro- and micro-nutrient content assessment. Additional indicators are available as add-ons, including root pathogen pressure, salinity and sodicity, heavy metals, boron and potentially mineralizable nitrogen. For more information and how to send a sample, contact the department:
Cornell University Comprehensive Assessment of Soil Health
http://soilhealth.cals.cornell.edu/ or [email protected]
Your county extension office may also accept samples; contact them to check. Many CCE offices can mail the samples for you, assist in analyzing results, take payment for testing or provide forms and boxes to farmers if they wish to mail their own samples. Results will be mailed in approximately 2 weeks.
To learn about the soil types on your property, a useful tool available in almost all NY counties is the USDA-NRCS Soil Survey that consists of soil maps and descriptions of soil characteristics and capabilities.
As with any garden, soil preparation is what really counts when it comes to being successful growing in containers. It’s the foundation. It’s the staff of life. Pick your life-giving metaphor and you get the idea.
In other words, select the right potting mix recipe for your plants and they will thrive. Skimp on the soil and you’ll get weak, non-productive plants that require more work to maintain and are susceptible to all kinds of pest problems.
What is the perfect mix? That depends. Every professional gardener has his own “secret” recipe just like every Italian grandmother has her own way of making tomato sauce. However, most experts agree that a good container medium should be lightweight and drain well, yet contain enough organic matter to hold moisture and nutrients even through hot, dry weather.
Get your potted crops off to a great start and keep them healthy with premium quality potting soils. Designed to provide root support, moisture retention and healthy nutrients, these organic mixes will give you maximum results.
Note: Ordinary garden soil is not recommended as a potting mix. It’s usually too heavy and may contain weed seeds, diseases, and insect pests.
Most commercial potting mixes are the seller’s best attempt to provide for aeration, water retention and nutrients. Of course, not all commercial soils are the same. The old adage “you get what you pay for” can really come into play here. Avoid inexpensive soils that just say “topsoil” or “compost” on the label. That mysterious topsoil may be anything and could very well be old, tired soil that comes from land that’s been farmed to death. Poor topsoil can be completely depleted of nutrients, but rich in nasty chemical pesticides and herbicides, another leftover from life down on the farm. Something merely labeled “compost” could very well be made from toxic sludge (often called biosolids) or just ground up wood chips and nothing else. Play it safe and buy quality organic potting soil.
So what should you look for? “Certified Organic,” that’s what. Beyond that, look for specific ingredients. Don’t buy mystery soil. Remember the old sci/fi classic, Soylent Green? It pays to know the contents of your food or the food of your plants.
Tip: Store leftover soil in a tightly sealed bag to keep out soil-dwelling pests, like fungus gnats. Read our article Contaminated Potting Soil and Compost to learn more.
Make Your Own
Of course, you don’t have to purchase potting soil. You can make your own. Sure, it’s more work, but it can be more gratifying, plus you’ll know the exact contents of the soil since you’re the one who has mixed it up. A good potting mix recipe contains sterile garden loam, sand, peat moss (or coconut coir) and other additives as needed.
#1 SOILLESS MIX
Not just any grow medium… FoxFarm® Light Warrior is packed with beneficial microbes (mycorrhizae) to stimulate root growth, humic acid to promote seed germination and earthworm castings to help plants thrive. It’s the perfect fast-draining, lightweight mix for your indoor/ outdoor gardens. Available in a 1.0 cu ft bag.
Classic Soil-Based Mix:
- 1 part peat moss or mature compost
- 1 part garden loam or topsoil
- 1 part clean builder’s sand or perlite
The organic material in the above mix provides structure and the sand will improve drainage. A balanced, slow-release organic fertilizer may also be added to the mix.
Cornell Soilless Mix (adapted for organic growers*):
- 1/2 cubic yard peat moss or coconut coir
- 1/2 cubic yard perlite
- 10 lbs. bone meal
- 5 lbs. ground limestone
- 5 lbs. blood meal
* This soilless mix was developed at Cornell University for commercial growers, but is easily adapted for home use. I have substituted select organic fertilizers in place of synthetic fertilizers.
The Perfect Raised Bed Soil Mix
Good organic garden soil is the single most important ingredient for healthy, nutritious vegetables. It is loose and fluffy — filled with air that plant roots need — and has plenty of nutrients and minerals essential for vigorous plant growth and bountiful yields. Filling your raised beds is an opportunity to get high-quality soil and to fine-tune the mix of fertilizers and amendments.
The following soil mix was developed by Planet Natural to fill a 4’ X 8’ raised bed one foot deep (32 cu ft).
5 bags Black Gold Peat Moss, 2.2 cf x 5 = 11 cf
3 bags Teufel’s Organic Compost, 3 cf x 3 = 9 cf
4 bags Worm Castings, 1 cf x 4 = 4 cf
3 bags Organic Chicken Manure, 1 cf x 3 = 3 cf
2 bag Therm-O-Rock Organic Vermiculite, 2 cf x 2 = 4 cf
3-6 lbs Azomite
1-2 lbs Kelp Meal
3-6 lbs Oyster Shell Flour
2-4 lbs All-Purpose Fertilizer
Have on hand all the ingredients for your soil mix before you start filling the beds, and pre-mix as much as possible, on a large tarp if necessary, to avoid pockets of peat, manure or any other ingredients.
Note: Do NOT use pressure treated wood or railroad ties for your raised bed frame because of chemical leaching.
There are a couple places where you can find loam ingredients, even if you live in the city. Loam ingredients will not harm goldfish and mosquito minnows. If you have koi in your pond, then you must choose a sterile soil that is free from parasites. For the rest of us mix…
2 parts clay soil
Can be found at a sand and gravel yard, your backyard, or near a river or lake.
1 part river sand (not ocean sand)
Can be found at a sand and gravel yard or near a river or lake. You can also purchase “playground” sand from a hardware store. Make sure it is not sand used for concrete. The best sand is the kind that has flecks of iron pyrite (which is not in playground sand). River sand often has iron pyrite. Sand and gravel yards also carry river sand.
1/2 to 1 part pea gravel or silt (optional)
Can be found near a river or lake, and your local hardware store. I do not care for pea gravel, because it makes it difficult to fertilize the lily plant.
Cost for a 5 gallon bucket of clay soil and a 5 gallon bucket of river sand from the sand and gravel yard = $6. This is a great deal, because it is far more expensive if you buy it already mixed from a nursery.
DIY potting soil: 6 Homemade potting mix recipes for the home and garden
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I’m a huge fan of container gardening, and I know I’m not alone. Urban and small-space gardening is on the rise, houseplants are strutting their stuff all over Instagram, and few people have the time and energy to dedicate to a large in-ground garden these days. But with hundreds of seedlings to start and over 50 large pots to fill each season, my container gardening habit used to come with a hefty price tag. When I started making my own DIY potting soil, however, I cut my container gardening budget by two-thirds! Here’s how I make homemade potting mix for all of my containers, houseplants, and seed-starting needs.
What is potting soil?
Before I introduce my favorite DIY potting soil recipes, let’s talk about what potting soil actually is. The most important thing to understand about potting soil is that it doesn’t actually contain real soil. Potting soil, also called potting mix, is a soilless blend of ingredients used to grow plants. Whether you’re starting seeds, rooting cuttings, potting up houseplants, or growing patio containers and hanging baskets, potting soil is the ideal growing medium for containerized plants. All good-quality potting mixes, including homemade potting soils, have a few things in common.
- They’re better draining than the average garden soil.
- Potting soil is more lightweight than garden soil.
- It’s easy to handle and consistent.
Making your own potting soil blends is easy and inexpensive.
Like commercial potting soils, you can make many different DIY potting soil blends, each with a different texture, nutritional content, density, and water-holding capacity, all matched to the needs of your plants. Carefully select the ingredients you use and combine them in the correct ratios to tailor each DIY potting soil you make for the specific needs of each plant you’re growing.
- Lighter, finer-textured mixes are best for use when starting seeds and rooting cuttings.
- Mixes containing a high percentage of coarse sand or pine bark are best for potted trees and shrubs.
- DIY potting soil with a sandy or gravely texture is ideal for cactus and succulent growing.
- When growing a mixture of annuals, perennials, vegetables, and tropicals, the best fit is a general, all-purpose potting mix – one that’s suitable for growing lots of different kinds of plants.
There are dozens of specialized potting soil mixes you can make.
Mix and match several ingredients to make your own potting soil blends that are tailored to the needs of the plants you’re growing.
Potting soil ingredients
Most commercial and homemade potting soils consist of a blend of the following ingredients:
Sphagnum peat moss:
The primary ingredient in most potting soils is sphagnum peat moss. A very stable material, peat takes a long time to breakdown and is widely available and inexpensive. It bulks up potting mixes without adding a lot of weight, and once wet, it holds water fairly well.
Sphagnum peat moss is well-draining and well-aerated, but it’s very low in available nutrients and it has an acidic pH, typically ranging between 3.5 and 4.5. Limestone is added to peat-based potting mixes to help balance the pH. I use bales of Premier brand peat moss for my homemade potting soil, blended with crushed limestone at a rate of 1/4 cup lime for every 6 gallons of peat moss.
Sphagnum peat moss is the most prevalent ingredient in potting soil.
A by-product of the coconut industry, coir looks and acts a lot like sphagnum peat moss in both commercial and DIY potting soil blends. It has more nutrients than peat moss and lasts even longer, but it’s more expensive to purchase. Coir fiber’s pH is close to neutral.
Often sold in compressed bricks, coir fiber is considered by many to be more sustainable than sphagnum peat moss. BotaniCare is one available brand of compressed coir fiber.
Perlite is a mined, volcanic rock. When it’s heated, it expands, making perlite particles look like small, white balls of Styrofoam. Perlite is a lightweight, sterile addition to bagged and homemade potting mixes.
It holds three to four times its weight in water, increases pore space, and improves drainage. With a neutral pH, perlite is easy to find at nurseries and garden centers. One popular brand of perlite is Espoma perlite.
Perlite is a volcanic mineral that’s mined and then heated until it expands.
Vermiculite is a mined mineral that is conditioned by heating until it expands into light particles. It’s used to increase the porosity of commercial and DIY potting soil mixes. In potting soil, vermiculite also adds calcium and magnesium, and increases the mix’s water-holding capacity.
Though asbestos contamination was once a concern with vermiculite, mines are now regulated and regularly tested. Organic bagged vermiculite is my favorite source.
Vermiculite particles are much more fine than perlite, but it, too, is a mined mineral deposit.
Coarse sand improves drainage and adds weight to potting mixes. Mixes formulated for cacti and other succulents tend to have a higher percentage of coarse sand in their composition to ensure ample drainage.
Add pulverized calcitic limestone or dolomitic limestone to peat-based potting soils to neutralize their pH. Use about 1/4 cup for every 6 gallons of peat moss. These minerals are mined from natural deposits and are readily available and inexpensive. Jobe’s is a good brand of lime for use in DIY potting soil.
Add fertilizers to peat-based potting soils because these mixes don’t naturally contain enough nutrients to support optimum plant growth. A good DIY potting soil recipe includes a natural fertilizer, derived from a combination of mined minerals, animal by-products, plant materials, or manures, rather than a fertilizer that’s comprised of synthetic chemicals.
I use a combination of several natural fertilizer sources for my homemade potting mixes. Sometimes I add a commercially-made, complete organic granular fertilizer, such as Dr. Earth or Plant-Tone, and other times I blend my own fertilizer from cottonseed meal, bone meal, and other ingredients (my favorite fertilizer recipe is provided below).
Commercial granular fertilizers make fine additions to DIY potting soil, if you don’t want to blend your own fertilizer.
Composted wood chips:
Composted wood chips lighten up potting mixes by increasing the pore sizes, and allowing air and water to travel freely in the mix. They’re slow to breakdown but may rob nitrogen from the soil as they do, so the addition of a small amount of blood meal or alfalfa meal is necessary when using composted wood chips as an ingredient in DIY potting soil recipes. Use composted wood chips in potting mixes designed for potted perennials and shrubs. To make your own, get a load of wood chips from an arborist and let them compost for a year, turning the pile every few weeks.
Containing billions of beneficial microbes, and with superior water-holding capacity and nutrient content, compost is an excellent addition to DIY potting soil. Because it plays such a huge role in promoting healthy plant growth, I use it in all of my general homemade potting soil recipes. But, I don’t include it in recipes for seed-starting as it’s too heavy for young seedlings. I use leaf compost from a local landscape supply yard, but bagged compost from Dr. Earth Compost or Coast of Maine are other favorites.
Good quality, DIY potting soil should be light and fluffy, with a well-blended mixture of ingredients. When it’s dried out, it does not shrink significantly or pull away from the sides of the container.
By blending the right ingredients together in the correct ratios, it’s easy to make DIY potting soil recipes.
How to make your own homemade potting soil
Mixing your own potting soil blend is easy, and it means you have complete control of one of the most critical steps in the growing process. For container gardeners, a high-quality potting soil is a must. Making your own potting soil allows you to better cater to the needs of your plants. The results are more stable and consistent, and you save a ton of money.
The following DIY potting soil recipes use a combination of the ingredients I listed above. Mix large volumes of homemade potting soil in a cement mixer or a spinning compost tumbler. To make smaller quantities, blend the ingredients in a wheelbarrow, mortar mixing tub, or a large bucket. Be sure to mix everything thoroughly to ensure a consistent result.
I mix my homemade potting soil ingredients in my tractor cart, but you can use a wheelbarrow or large bucket, too.
General potting soil recipe for flowers, tropicals, and vegetables
6 gallons sphagnum peat moss or coir fiber
4.5 gallons perlite
6 gallons compost
1/4 cup lime (if using peat moss)
1 & 1/2 cup of the DIY container fertilizer blend found below OR 1 & 1/2 cups of any granular, complete, organic fertilizer.
DIY container fertilizer blend:
2 cups rock phosphate
2 cups greensand
½ cup bone meal
¼ cup kelp meal
Potting soil recipe for potted trees and shrubs
3 gallons compost
2.5 gallons coarse sand
3 gallons sphagnum peat moss or coir fiber
2.5 gallons composted pine bark
3 gallons perlite
2 TBSP of lime (if using peat moss)
1 cup granular, organic fertilizer (or 1 cup of the DIY container fertilizer blend found above)
1/4 cup organic cottonseed meal, if growing acid-loving trees and shrubs
Potting soil recipe for succulents and cactus
3 gallons sphagnum peat moss or coir fiber
1 gallon perlite
1 gallon vermiculite
2 gallons coarse sand
2 TBSP lime (if using peat moss)
Potting soil recipe for seed starting
2 gallons sphagnum peat moss or coir fiber
2 gallons vermiculite
1 gallon coarse sand
3 TBSP lime (if using peat moss)
Seed-starting mixes are lighter and finer in texture. Vermiculite is a better choice than perlite due to its smaller particle size.
Homemade potting soil for transplanting seedlings
2 gallons sphagnum peat moss or coir fiber
2 gallons vermiculite
1 gallon finely screened compost
3 TBSP lime (if using peat moss)
2 TBSP granular, organic fertilizer (or 2 TBSP of the DIY container fertilizer blend found above)
Potting soil recipe for houseplants
2 gallons sphagnum peat moss or coir fiber
1.5 gallons perlite
2 cups coarse sand
3 TBSP lime (if using peat moss)
2 TBSP granular, organic fertilizer (or 2 TBSP of the DIY container fertilizer blend found above)
When repotting houseplants, use your own homemade mix for great results.
When making DIY potting soil, use the batch as quickly as possible. But if storage is necessary, place the mix in sealed plastic bags in a cool, dry place.
Watch this quick little video for a lesson on how I mix a batch of my DIY potting soil:
For more on how to garden successfully in containers, check out my book, Container Gardening Complete (Cool Springs Press, 2017).
If you enjoy growing in containers, you might also enjoy these related posts:
- The best vegetable varieties for growing in containers
- Easy container rose gardening
- A container gardening tip list for success
- The best organic fertilizers for container gardening
- How to maintain container plantings
Have you made your own homemade potting soil before? Share your experience with us in the comment section below.
What is soil?
Note Number: AG0058
Published: May 1998
Updated: May 2009
Soil is the loose surface material consisting of inorganic particles and organic matter that covers most of the land surface. Soil provides the structural support and the source of water and nutrients for plants used in agriculture.
Soils vary greatly in their chemical and physical properties which depend on their age and on the conditions (parent material, climate, topography and vegetation) under which they were formed.
Processes such as leaching, weathering and microbial activity combine to make a whole range of different soil types, each of which has particular strengths and weaknesses for agricultural production.
This Agriculture Note provides a brief introduction to soils and the major soil components.
Inorganic material is the major component of most soils. It consists largely of mineral particles with specific physical and chemical properties which vary depending on the parent material and conditions under which the soil was formed. It is the inorganic fraction of soils which determines soil physical properties such as texture and has a large effect on structure, density and water retention.
The texture of soil is a property which is determined largely by the relative proportions of inorganic particles of different sizes.
In Australia the following five size fractions are used to describe the inorganic fraction of soils:
- Gravel – particles greater than 2 mm in diameter.
- Coarse sand – particles less than 2 mm and greater than 0.2 mm in diameter.
- Fine sand – particles between 0.2 mm and 0.02 mm in diameter.
- Silt – particles between 0.02 mm and 0.002 mm in diameter
- Clay – particles less than 0.002 mm in diameter.
Quartz is the predominant mineral in the sand fraction of most soils. Sand particles have a relatively small surface area per unit weight, low water retention and little chemical activity compared with silt and clay.
Silt has a relatively limited surface area and little chemical activity. Soils high in silt may compact under heavy traffic and this affects the movement of air and water in the soil.
Clays have very large surface areas compared with the other inorganic fractions. As a result clays are chemically very active and are able to hold nutrients on their surfaces. These nutrients can be released into soil water from where they can be used by plants. Like nutrients, water also attaches to the surfaces of clays but this water can be hard for plants to use.
There are many different types of clays. The ability of clays to swell and to retain a shape into which they have been formed, as well as their sticky nature, distinguish them from sand and silt.
Soil textural class
The relative proportion of sand, silt and clay particles determines the physical properties of soil including the texture. The surface area of a given amount of soil increases significantly as the particle size decreases. Consequently, the soil textural class also gives an indication of some soil chemical properties.
The exact proportions of sand, silt and clay in a soil can only be determined in a laboratory but a naming system has been developed to approximately describe the relative proportions of sand, silt and clay in soil. This classification of soil can be undertaken in the field where particular properties indicate possible textural classes.
To estimate texture in the field, crush a small sample of soil (10 to 20g) in one hand. After removing any gravel or root matter, work the soil in the fingers to break down any aggregates which may be present. With the sample moist but not sticky, the textural class can be estimated by the feel of the sample between the fingers
Classes of Texture – in order of increasing clay content (Adapted from Leeper and Uren, 1993)
Textural class description
Sand – A sand has a loose gritty feel and does not stick together. Individual sand grains can be seen or felt.
Loamy Sand – In a loamy sand particles barely stick together and a moulded piece of soil just holds its shape.
Sandy Loam – A sandy loam sticks together more than a loamy sand but can be easily broken. Individual sand grains can be felt and heard if a wet sample is rubbed between the index finger and thumb and held close to the ear.
Silty Loam – A silty loam is like a loam but has a smooth silky feel when a moist sample is pushed between the index finger and thumb. On drying a sample can form a hard lump but this may be broken by hand.
Loam – A loam breaks into crumbs but will tend to stick together. Sand grains cannot be felt in a moist sample which when squeezed will retain its shape when handled freely. Loams are usually soft to the feel.
Sandy Clay Loam – A sandy clay loam is like a clay loam but sand grains can be felt (and heard – see Sandy Loam)
Silty Clay Loam – A silty clay loam is like a clay loam but silty as well and smooth to the touch.
Clay Loam – More easily moulded into a shape than a loam, a clay loam rolls out to a thin ribbon between the palms while a loam will break-up. When dry a clay loam will form a lump but is not as tough to break as a clay.
Sandy Clay – A sandy clay is like a clay but sand grains can be felt (and heard – see Sandy Loam).
Silty Clay – A silty clay is like a clay but smoother.
Clay – Clays are tough and can be moulded into shapes when moist. Clays form a long flexible ribbon when rubbed between the palms and the ribbon can often be bent into a “U” shape without breaking. Clays dry into very hard clods.
It should always be remembered that soil texture often varies with depth and that the properties of the topsoil are affected by the properties of the subsoil.
Structure is the arrangement of soil particles and the pore spaces between them. A soil with structure which is beneficial to plant growth has stable aggregates between 0.5 and 2 mm in diameter. Such soils have good aeration and drainage.
The inorganic minerals of soils consist primarily of silicon, iron and aluminium which do not contribute greatly to the nutritional needs of plants. Those in the clay fraction have the capacity to retain nutrients in forms which are potentially available for plants to use.
The organic matter of soil usually makes up less than 10% by weight of soil. It can be subdivided into the living and the non-living fractions. The non-living fraction contributes to the soil’s ability to retain water and some nutrients and to the formation of stable aggregates.
The organic matter fraction of soils comes from the decomposition of animal or plant products such as faeces and leaves. Soil organic matter contributes to stable soil aggregates by binding soil particles together.
Plants living in soil continually add organic matter in the form of roots and debris. Decomposition of this organic matter by microbial activity releases nutrients for the growth of other plants.
The organic matter content of a soil depends on the rates of organic matter addition and decomposition. Soil micro-organisms are the primary agents responsible for the decomposition of organic matter such as plant residues. Initially, the sugars, starch and certain proteins are readily attacked by a number of different micro-organisms. The more resistant structural components of the cell wall are decomposed relatively slowly. The less easily decomposed compounds, such as lignin and tannin, impart a dark colour to soils containing a significant organic matter content.
The decomposition rate of organic materials depends on how favourable the soil environment is for microbial activity. Higher decomposition rates occur where there are warm, moist conditions, good aeration, a favourable ratio of nutrients, a pH near neutral and freedom from toxic compounds.
The soil contains numerous organisms ranging from microscopic bacteria to large soil animals such as earthworms. The soil micro-organisms include bacteria, fungi, actinomycetes, algae, protozoa and nematodes.
The diversity of soil organisms can both assist and hinder plant growth. Beneficial activities include organic matter decomposition, nitrogen fixation, transformation of essential elements from one form to another, improvement in soil structure through soil aggregation, and improved drainage and aeration.
Under some circumstances soil organisms compete with plants for nutrients.
Bacteria are the smallest and most numerous micro-organisms in the soil.
They make an important contribution to organic matter decomposition, nitrogen fixation and the transformation of nitrogen and sulphur.
The fungi and actinomycetes contribute beneficially to organic matter decomposition. The group of large soil animals includes earthworms, which incorporate organic matter into the soil as well as improving aeration and drainage by means of their channels. Some soil fungi, nematodes, and insects feed on roots and lateral shoots to the detriment of plants.
LEEPER, G.W. and UREN, N.C. (1993) Soil Science, An Introduction. 5th edition, Melbourne University Press.
The previous version of this Information Note was published in May 2008.
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Soils are formed through a very complex process involving the nature of the parent bedrock, climate, animals, vegetation, slope of the landform, and length of time the soil has been in existence. Most of Michigans soils were developed from glacial sediments deposited during the Ice Age. As the huge ice sheets moved southward over Michigan, they picked up, eroded, and deposited rocks, sand, gravel, and silt. When the ice receded the material collected in and underneath the ice sheets was left behind. Since then the surface layers have been changed by the action of water, ice, wind, plants, animals, and people. Thus, there are a great variety of soils, and in Michigan, soil characteristics may differ dramatically from region to region, from field to field, or even within a single field.
Soils are characterized by the differences in the various layers (horizons). In natural settings, the mineral soil is overlain by the O (organic) soil horizon, which is made up of decaying leaves, twigs, etc. (see below).
The topmost mineral horizon is called the A horizon and contains the partially decomposed vegetable matter called humus, which helps to hold moisture and provide food for plants to grow. In forest soils, the dark A horizon is underlain by a light-colored E horizon, from which various amounts of clay, Fe and Al have been removed by infiltrating water. The B horizon (below the E and A) is the zone that accumulates these compounds. It is often brown in color.
The soils of Michigan vary greatly. Sandy soils are dominant in the western and northern portions of the Lower Peninsula; clays and loams, in the southern Lower Peninsula. The size of particles, or texture, varies in different kinds of soil. Soils with a loam texture have a combination of soil particle sizes; there are sandy loams, silty loams, loamy sand, and clay loams.
Loam soils are best for plant growth because sand, silt, and clay together provide desirable characteristics. First, the different-sized particles leave spaces in the soil for air and water to flow and roots to penetrate. The roots feed on the minerals in the suspended water. Deep sands do not hold moisture well and are often infertile. Clays hold moisture better than sands and may be more fertile, but they tend to swell when they get wet, which may limit the movement of water and roots. Clays crack when they dry and the clods become very hard and difficult to manage (for humans as well as plants!). A desirable soil is a loam with enough sand to drain well yet with enough clay and silt to hold to hold moisture. Silt-sized grains also contain nutrients and help make a soil workable.
Some soils (Histosols) contain a large amount of partially decayed vegetation (humus) and are called peat or muck. They are often used for growing vegetables because of their high fertility. Thus, the distribution of various kinds of soils in Michigan relates closely to the various types of crops grown and how productive the agriculture is.
Soil maps can be created, and the soils of a region examined, along a number of different scales and with differing degrees of accuracy and complexity. The map below shows the soils of the western Great Lakes region at a very general level, in fact at the broadest and most generalized level: soil orders (of which there are only 12 in the world). The six major soil orders in Michigan each have their own web page (use the “back” key to get to the list).
The soil information used for the three soil maps below, in this section of the GEO 333 web page, was Natural Resource Conservation Service 1994 STATSGO data. STATSGO was compiled at 1:250,000 and designed to be used primarily for regional, multistate, State, and river basin resource planning, management and monitoring.
(Web source: http://www.ftw.nrcs.usda.gov/stat_data.html; Metadata: http://www.ftw.nrcs.usda.gov/metadata/mi.html)
A more accurate map of the major soil orders in Michigan is shown below. Note how Spodosols dominate the UP and northern lower peninsula, except of clayey landscapes (here you’d find Alfisols) and the wettest swamps (here you’d find Histosols), and how Alfisols dominate the southern lower peninsula.
The two maps below show even more detail, breaking the soil orders down into suborders and then Great Groups.
Another way to look at soils is by their major associations. A soil association represents several types of soil that commonly are found together.
But what about soils in neighboring areas and states? The map below provides some information along these lines.
Parts of the text on this page have been modified from L.M. Sommers’ book entitled, “Michigan: A Geography”.
This material has been compiled for educational use only, and may not be reproduced without permission. One copy may be printed for personal use. Please contact Randall Schaetzl ([email protected]) for more information or permissions.
ARTICLE – What is Clay Loam
Clay loam is a soil mixture that contains more clay than other types of rock or minerals. A loam is a soil mixtures that is named for the type of soil that is present in the greatest amount. The particles of clay are very small, which is one of its most important characteristics. For this reason, loams that contain a great deal of clay tend to be heavy, because they are so dense. While this soil type can be difficult to work with, it can also be improved to be a very good growing medium.
The density of clay is the cause of the two biggest drawbacks of clay loam. When it is very wet, it swells to retains water, which makes it difficult to work with. Over time, this poor drainage can also stunt plant growth. Dry clay shrinks but stays packed, forming dense clods and cracking the soil surface. These drawbacks can be lessened by adding organic matter over time.
Usually clay loam contains a good deal of plant nutrients and supports most types of plants and crops. Clay loams can be improved to create better drainage without too much difficulty. In some wet weather or climates, the drainage problems may be harder to overcome.
Probably the best way to improve clay loam is to regularly add organic matter in the form of compost or humus. Another good idea is to dig in more bulky matter, such as shredded leaves. This will help to keep clods from forming when dry. When wet, it will allow more water and air to pass through, leading to a less packed, better drained texture. As clay already contains a good deal of nutrients, improving the texture makes it a perfectly good soil mixture for most plants.
There are other methods that can be used to improve clay loam. One is to plant yearly in the same places. Old roots that are left behind will create extra space in the soil. Digging in plants that died on the spot will also help. It’s often easier to dig clay in the fall, when the loam is drier. This can be done in the spring, but there may be fewer opportunities.
Clay soil can be identified by the fact that it is sticky when wet. Then it can be easily rolled between the fingers to form lumps or balls. These will retain their shape without crumbling.
TS1 – Premium sandy loam topsoil
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