People choose do-it-yourself projects for many reasons. Some like the satisfaction of completing a task on their own, while others like the idea of having absolute control over their materials, methods and finished product. Another reason people choose do-it-yourself projects is price. Generally speaking, providing your own labor will produce a product for a much low price than hiring out the work would.

Building your own organic potting soil is no different than any other do-it-yourself project. It allows the gardener to save money while maintaining control over every aspect of the soil building process. Some might also argue that it produces a superior product.

However, before we dive into soil recipes, let’s first examine some of the more common ingredients used in potting soils. There is no shortage of organic soil amendments to choose from. Once an understanding of the physical properties and nutrient value of each ingredient is reached it then becomes possible to customize soil mixtures not only for particular crops, but also for specific periods in a plant’s life cycle (blooming or flowering periods).

Base Ingredients of Potting Mixes

The base ingredients of a soil are the substances that make up the bulk of the soil itself. These are the ingredients that are most responsible for the soil’s physical properties and texture. Some of these also make up the backbone of the nutrient content.

Sphagnum peat moss

Sphagnum peat moss has been a popular soil additive since the inception of potting soils. The physical properties of peat moss allow for high moisture retention, as well as high oxygen content. This combination of water and oxygen retention makes a great environment for developing roots and is the main reason peat moss is the most popular ingredient in premade potting soils. It is not uncommon for peat moss to make up 30 to 60% of a premade soil mixture.

Coco coir

Many soil companies are incorporating coco coir (coconut husks) as either the base or secondary ingredient in their potting soil mixes. Coco coir is a by-product of the coconut industry and is more environmentally friendly than sphagnum peat moss. It is able to hold moisture and oxygen like peat moss; in fact, it actually has slightly higher oxygen retention. This fact alone has made coco coir’s popularity increase among indoor gardeners and greenhouse horticulturalists.

Compost

Compost is a general term referring to aged and broken down organic matter. It can be made from a number of different sources, but it’s usually derived from plant material or manure. Although compost usually isn’t used in as high of a volume as peat moss or coco coir, its role as a base ingredient is just as crucial. Not only does compost have significant nutrient value, but it also provides an abundance of microbial life to the soil mixture. These beneficial microorganisms are the foundation for nutrient uptake and the stimulation of root development.

Worm castings

Like compost, worm castings—or, vermicompost—are a significant source of nutrient value and beneficial microorganisms. Revered by many organic growers as the best soil additive available, worm castings are known to enrich soils and improve disease resistance in crops. If you choose to use worm castings as an ingredient in your potting soil, be sure to purchase pure worm castings. There are many products on the market that are labeled as worm castings but only contain a small percentage of actual worm castings in their composition.

Aeration additives

Perlite

Perlite is expanded volcanic glass and adds air pockets to soils. Soils with added perlite will dry out quickly between each watering, which gives a grower more control over a feeding regiment. Perlite is light weight and relatively inexpensive, which makes it the most popular choice among commercial potting soil manufacturers.

Pumice

Pumice is a type of volcanic rock that is naturally porous. Like perlite, pumice has the ability to add air pockets in a soil, which results in higher oxygen content around the plant’s roots. Pumice is less commonly used by commercial manufacturers, however, simply because it is heavy and, therefore, expensive to ship.

Individual organic ingredients

By using individual organic ingredients along with the base, a grower can tailor their soil to meet the needs of any crop. Most of the following ingredients can be obtained at your local hydroponic retailer or local garden supply store.

Common nitrogen (N) ingredients:

Blood meal

This is an extremely rich, fast-releasing nitrogen source. Blood meal is a great additive for plants that require high amounts of nitrogen.

Fish meal

Fish meal is another fast-releasing nitrogen source. It’s a great nitrogen additive that enhances microbial life in the soil. Fish meal also contains a significant amount of phosphorus, which helps trigger root development.

Feather meal

Feather meal is a slow-releasing nitrogen source best used on plants that require high amounts of nitrogen over a three to four month period.

Soybean meal

This slow-releasing nitrogen source is not quite as slow as feather meal. It’s a great additive for plants that require adequate nitrogen for two to three months and that need a little phosphorus boost to help promote fruiting or flowering.

Bat guano (high nitrogen)

There are many compositions of bat guano on the market, including high-nitrogen bat guano. High-nitrogen bat guano is rich in micronutrients, beneficial microbes and, of course, nitrogen. This beneficial diversity combined with fast-releasing nitrogen makes high-nitrogen bat guano the fertilizer of choice for many organic growers.

Common phosphorus (P) ingredients:

Bat guano (high phosphorus)

High-phosphorus bat guano is an excellent source of phosphorus that is known to not only increase flower and fruit sets, but also their size, aroma and flavor. Many brands of high-phosphorus bat guano are also a great source of calcium.

Bone meal

This excellent source of phosphorous is revered for its ability to promote strong root development. Bone meal is also a great source of calcium.

Fish bone meal

Fish bone meal is basically the same thing as bone meal except it is derived from fish. It is a great source of phosphorus and calcium.

Seabird guano

Seabird guano, like bat guano, is known to increase the amount and size of flower and fruit sets. It is also an excellent source of phosphorus and micronutrients.

Rock phosphate

Rock phosphate is a slow-releasing phosphorus source that is commonly extracted into a liquid form to increase availability. It is best used for plants that need a slow and constant release of phosphorus.

Common potassium (K) ingredients:

Hardwood ash

This is the original source of potash fertilizers. Hardwood ash can be used as a direct soil additive to increase potassium levels; however, most of the time, it has already been added to the compost for that same purpose.

Kelp meal

Kelp meal is a source of readily available potassium and a variety of micronutrients and plant hormones. This great soil additive can increase overall plant health and vigor.

Greensand

Greensand is a slow-releasing potassium source. Generally speaking, greensand is used to improve soil’s condition rather than boost potassium content.

Langbeinite

Langbeinite is a natural occurring mineral which is water soluble. It is a good source of potassium, sulfur and magnesium.

Secondary and trace elements:

Oyster shell

This is an excellent source of calcium that will accelerate root development and, in turn, improve nutrient uptake. Oyster shell also works as a pH buffer, helping to keep the soil from becoming too acidic.

Dolomite lime (sweet lime)

Dolomite lime is a great pH buffer for any soil composition and—like oyster shell—it ensures the soil’s pH doesn’t turn too acidic. It also a rich source of calcium and magnesium.

Glacier Rock Dust

This soil amendment revitalizes trace elements and provides a foundation of minerals for healthy plant growth.

Alfalfa meal

Alfalfa meal is rich in trace elements, but it’s the abundance of natural growth stimulators in this product that has gained recognition among organic horticulturalists. Alfalfa meal will accelerate growth rates while promoting abundant fruit or flowers.

Beneficial microorganisms

Although many common soil ingredients already contain a good amount of beneficial microorganisms, it has become second nature for many organic gardeners to supplement additional microorganisms into their soil. Three beneficial microorganisms are commonly used by horticulturalists are trichoderma, mycorrhiza and bacteria.

Soil recipes

As written, the recipes below will produce around 2 cu. ft. of soil—or, roughly the amount you would find in a single large bag of potting soil. Of course, the ingredients can be proportionally increased or decreased to produce the desired amount of potting soil. Also, feel free to add your favorite beneficial microorganism supplement to increase the beneficial microbial population.

Indeed, do not take these recipes as though they were written in stone. Use them as a reference or as a way to inspire some thought into the nutrient content of your own potting soil and how this coincides with the life cycle of your plants.

To make each mix, simply combine all of the ingredients by hand, rake or shovel in a kiddie pool, tarp, large wash bin or plastic storage container. Just make sure to mix the ingredients thoroughly to ensure a uniform soil mixture.

Basic potting soil recipe

This basic recipe creates a soil with a high air-to-water ratio and can be used for almost any variety of plant. This is a great soil recipe for growers wishing to complement their homemade soils with liquid teas or fertilizers. This is also a great starting recipe to use as the foundation for custom, plant-specific soils, which can be created by with addition of other individual ingredients.

  • 1/2 cu. ft. (60 cups) compost
  • 1/2 cu. ft. (60 cups) sphagnum peat moss
  • 1/2 cu. ft. (60 cups) coco coir
  • 20 cups perlite
  • 5 cups worm castings
  • 1/2 cup oyster shell
  • 2 tbsp. langbeinite
  • 1 tbsp. glacier rock dust

Enhanced vegetative potting soil recipe

This nitrogen-rich soil mixture is great for the vegetative stage of fast-growing annual plants that will later be transplanted, or for green leafy crops that spend their whole life cycle in a perpetual vegetative stage. This mix is very well-aerated and will promote strong root growth and vigorous vegetative growth.

  • 1/2 cu. ft. (60 cups) sphagnum peat moss
  • 1/4 cu. ft. (30 cups) coco coir
  • 1/4 cu. ft. (30 cups) compost
  • 1/4 cu. ft. (30 cups) perlite
  • 10 cups worm castings
  • 10 cups pumice
  • 2 cups fish meal
  • 1 cup oyster shell
  • 1/2 cup alfalfa meal
  • 1/2 cup soybean meal
  • 1/4 cup kelp meal
  • 1/4 cup fish bone meal
  • 2 tbsp. langbeinite
  • 1 tbsp. glacier rock dust

Enhanced fruit/flower potting soil recipe

This soil recipe is designed for plants that are ready to fruit or flower. In particular, this recipe works great for ornamentals that are already in bloom and for fast-growing annuals that are entering their fruiting or flowering stage.

  • 1/2 cu. ft. (60 cups) sphagnum peat moss
  • 1/4 cu. ft. (30 cups) coco coir
  • 1/4 cu. ft. (30 cups) compost
  • 1/4 cu. ft. (30 cups) perlite
  • 10 cups pumice
  • 5 cups worm castings
  • 3 cups bat guano (high phosphorus)
  • 1 cup fish bone meal
  • 1 cup oyster shell
  • 1/2 cup seabird guano
  • 1/4 cup alfalfa meal
  • 1/4 cup fish meal
  • 2 tbsp. langbeinite
  • 1 tbsp. glacier rock dust

Entire life cycle soil recipe (for heavy feeders)

This soil mixture is designed to meet the demands of heavy feeding, fast-growing annual plants throughout their entire life cycle. This soil is powerful and should only be used on plant varieties that are known to be heavy feeders. The organic fertilizers in this soil mixture will sustain a heavy-feeding crop for about three months. The soil is designed to break down in a manner that first delivers readily available nitrogen for a vigorous vegetative stage (for about a month) then, as the soil’s composition changes, it will start to release more elements specific to fruiting/flowering.

  • 1/2 cu. ft. (60 cups) compost
  • 1/2 cu. ft. (60 cups) sphagnum peat moss
  • 1/2 cu. ft. (60 cups) coco coir
  • 1/4 cu. ft. (30 cups) perlite
  • 20 cups pumice
  • 15 cups worm castings
  • 2 cups blood meal
  • 2 cups fish meal
  • 2 cups bat guano (high phosphorus)
  • 1 cup oyster shell
  • 1 cup dolomite lime
  • 1 cup soybean meal
  • 1 cup bat guano (high nitrogen)
  • 1 cup bone meal
  • 1 cup fish bone meal
  • 1 cup rock phosphate
  • 3 tbsp. langbeinite
  • 1.5 tbsp. glacier rock dust

Although the process of building your own organic potting soil can be somewhat labor intensive (especially on a large scale), it is a relatively easy process overall that can be extremely rewarding. Not only is there a sense of accomplishment when you complete a homemade potting soil, but it is also a stride forward in creating the ultimate diet for your plants.

Growers who build soils specific to their crop’s ideal nutritional intake will not only see heightened garden performance, but less nutrient deficiencies, diseases, insect infestations and any other problems associated with an incomplete diet. Through your own experiments, you can find the perfect blend of ingredients required by your plants to enhance their performance and achieve optimal results.