How To Make Your Own Organic Gardening Soil

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January 18, 2021

The rising popularity of organic gardening and a desire to naturally achieve big, bountiful, quality crops have many people looking to make homemade soils for use in their gardens.

The best results require some forethought. What will the mix be made of and how can you formulate it for the specific plants being grown? Plants have various requirements; a mix for cacti and succulents would be much different from the soil used for annual, fast-growing herbaceous plants.

For the crops most indoor growers are interested in, a basic soil recipe requires a base, some aeration, compost, and nutrition.

The Base

Ingredients used for base materials include peat moss, coconut coir, and partially composted pine bark. There are pros and cons to each; make a decision based on availability, ingredient efficacy, and the environmental sources and impacts of each option. 

organic soil

The base makes up about one-third of a typical mix, so selecting the right balance is essential. Incorporating a blend of ingredients proves superior to choosing just one.

Aeration

Many ingredients help with aeration. A suitable drainage portion is critical; a mix that won’t drain is a mix that won’t grow!

Common drainage materials include perlite, rice hulls, volcanic rocks such as pumice and Scoria, expanded clay, and granular diatomite. These all have different capacities when it comes to retaining moisture. They also have various physical weights, shelf lives, and micronutrient profiles. Aeration makes up another one-third of the mix.

Before adding this component, consider where your garden will be. If you have an attic grow, for instance, and your soil ends up being super heavy, lugging it up the stairs might be challenging. 

Also, lightweight materials such as rice hulls and perlite are more likely to float to the top of the soil. A blend of elements of various sizes, shapes, and weights will work better than just one. 

Compost

The selection of high-quality compost for the third portion of the recipe is often one of the more challenging parts of building soil. It is easy to find a cheap, low-grade product, but go the extra mile to source something that is well broken down. The compost should have an even texture and be made with quality inputs. Better quality soil leads to healthier, more abundant crops.

Compost inputs vary widely, and building your own provides you with the most control. Plant waste from the garden, such as lawn clippings, fallen leaves, vegetable waste, and manure from cows, poultry, and sheep create high-quality composts that are quite cost-effective. Worm castings are also worth using, but due to their density and weight, you cannot use a lot.

The best-composted materials are aged for a long time. They have gone through the whole range of temperature zones and have been allowed a long maturation period. The final product should be dark, rich, and smell earthy. 

You can use a well-made compost to make up one-third of the mix volume, but try to keep the vermicast around the 10% or 15% mark to avoid making the soil too heavy.

Nutrition

While the compost provides a lot of nutrients, additional organic amendments and minerals can further enrich the soil and balance the pH of any peat moss or pine bark in the mix. A vast number of amendments can be put to use when building the soil: 

Plant-based inputs:

  • Hemp 
  • Soy 
  • Corn 
  • Coconut
  • Barley
  • Neem
  • Alfalfa 

Animal waste inputs: 

  • Blood meal 
  • Bone meal
  • Feather meal 
  • Guanos 

Sea-based inputs:

  • Kelp 
  • Crustacean waste 
  • Fish meal
  • Crushed oyster shells

All of the above pack significant amounts of nutrients and natural growth-promoting compounds capable of boosting plants. 

Find Balance

The trick to using any of these ingredients is not to use too much. Each one on its own is potent and high in nutrients. If the soil is too rich, it will be too hot to grow in. If you plan on using many different ingredients for diversity, it is essential to reduce the total amount of each amendment to achieve the same total volume of fertilizer. The application rate for each component will vary based on several factors. Always err on the side of caution. It is easier to apply less than to remove it when too much has been added. As a starting point, stick to an application rate of around 1% or 2% of the mix volume.

Adding a portion of minerals to complement your amendments is a good idea. These help adjust and buffer the pH of the mix while also providing cation exchanging and a backbone of trace minerals that increase the availability of the organic amendments.

organic soil

Limestone, dolomite, gypsum, potassium, magnesium sulfates, and basalt are among the most commonly utilized minerals. You don’t need an enormous amount of these components; it will vary based on what you are growing. 

For instance, a predominantly coco-based mix will not require much pH adjustment, so using a less reactive calcium source, like gypsum, and adding a little magnesium makes the most sense. In contrast, soil made with peat moss or pine bark often requires limestone or crushed oyster shell (which contain calcium carbonate) to raise the pH to an appropriate level. A quarter of a cup of lime per square meter of soil brings the pH from 5 to 7, so an enormous amount is not necessary. 

Ultimately, building your soil and perfecting it will take time, but starting with these proportions will get you in the right ballpark. Over time, you can continue to experiment and improve. These days, a variety of high quality, ready-to-use soils are also available at your local hydro store, so if you are pressed for time or lack the space to make your own, these are well worth considering.

Happy Growing!

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Cody J Garrett Tait

Cody is the owner of High Powered Organics and a second-generation Australian grower with more than a decade of experience in the horticulture industry. Cody works closely with growers locally and abroad, creating organic solutions for high output cropping. He achieves maximum results by combining aspects from permaculture, biodynamic farming, and Korean natural farming techniques. Cody’s main focus is finding natural, and sustainable ways to produce high-quality plants with a minimum of input.
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