Gardening

Is potting mix same as soil? Ingredients of potting mix

When you refer to the soil in gardening it is often a confusion between a potting mix and gardening soil. So what is a potting mix and why it is not soil and it should not be called so?

Plants grow perfectly well in healthy, well-amended garden soil so why can’t we use the same soil in our containers?

• One reason is drainage, on the ground in a garden bed gravity acts on the soil from deep underground, allowing excess water to drain down and away from plants’ roots. But in a container, the force of gravity can only pull water to the bottom of the container, where it may or may not find a drain hole to escape.
• At the same time, water is also drawn upward and is held in the soil by capillary action – the same force that pulls water slightly up the straw as it sits in a cup of water. (Remember ground clearance characteristic of a good container?) And the thinner the straw, the higher the water is pulled.
• Similarly, water gets pulled upward into the pores of soil – particularly in the tiny pores of our clay-heavy soils – where it’s held. So even with a good drain hole, some of the water just won’t be able to escape in a container filled with garden soil. And too much water in the soil for too long can cut off air circulation around the roots, which can stress or even kill a plant.
• Another reason is contamination of soil by chemicals, sewage, chemical fertilizers, and pesticides. To understand why a potting mix over garden soil is preferable, understand what a potting mix is.

Potting mix

Like soil, potting mix provides support & nutrition for plants but it is not soil. It’s a growth medium formulated specifically to help plants live happily in pots forming a comfortable ecosystem to support their growth.

Instead of garden soil, commercial potting mixes contain a combination of peat moss or coco peat, composted material like vermicompost, tree bark, cow manure, perlite, and vermiculite – and sometimes a few other components, depending on the mix.

Because of these ingredients, a good potting mix holds just the right amount of moisture while letting the excess drain away easily. It also maintains an airy, “fluffy” structure whether wet or dry. Potting mix just makes container life a lot easier for plants.

Soil less potting mix

In layman’s terms, soil-less potting mix (media) is something that does not have dirt/garden soil/mitti as an ingredient.

Advantages of soil-less potting mix over the soil- based

• Planters with mixes weigh 50-70% lighter than traditional mixes.
• Plants grow better because its fluffy and loose nature.
• Roots grow better and faster as they have more breathing space.
• Potting mix encourages moisture retention and excess water drainage, roots of the plant breath better.
• Adding periodic manuring or organic additives like bone meal, mustard cake, neem cake, etc. is easy and efficient. You rarely need hoeing. This can mimic the surface of the soil in the forest thus help build a great ecosystem for the plant to grow.
• Goes without saying that this mix holds nutrition longer than regular soil-based mixed.
• To some extent, you can be sure that your mix will have lesser fungal, pest, or insect infestation as normal garden soil/dirt may be contaminated.
• Re-potting becomes easier and efficient.
• Removal of weed is easier.

Ingredients of potting mix

There are no rules when it comes to creating a potting mix but certain organic ingredients have been in use for such a long time in gardening for their obvious benefits. Let’s understand why I chose these organic ingredients for my potting mix recipe

1. Vermicompost

Vermicompost (vermicompost, vermiculture) is the product of the decomposition process using various species of worms, usually red wigglers, white worms, and other earthworms, to create a mixture of decomposing vegetable or food waste, bedding materials, and vermicast (worm poop).

• Vermicompost is a great source of organic carbon and other necessary nutrients for plants.
• You can easily buy vermicompost these days from your local garden store or nursery.
• You may also use garden compost or homemade compost as well. Homemade compost is a great way to reduce kitchen waste.

2. Cow manure

• For decades cow manure (gobar khad in Hindi) has been used extensively in Indian farming methods and gardening because of its ease of availability.
• Cow manure is made up of digested grass and grain. Cow dung is high in organic materials and rich in nutrients. It contains about 3% nitrogen, 2% phosphorus, and 1% potassium (3-2-1 NPK).
• Cow manure also contains high levels of ammonia and potentially dangerous pathogens. Therefore it must be aged or composted before its use as cow manure fertilizer.
• Cow manure is an economic and easily available source of organic carbon, organic matter, and other plant nutrients. Which makes it an excellent ingredient for my potting mix.

3. Coco peat

Coco peat, also known as coir pith. coir fiber pith, coir dust, or simply coir, is made from coconut husks, which are byproducts of other industries that use coconuts.

• Coco peat does not have any nutritional value but it’s completely organic and has great water holding capacity. It also acts as a neutralizer for heavy mediums like vermicomposting and cow manures.
• Coco peat is used to add further light-ness, water holding capacity, and conditioning to the potting mix.

Commercially available cocopeat blocks have a higher level of salt contains which may affect the quality of your potting mix and therefore subsequently hinder the growth of your plant, therefore before mixing it into your mix, soak cocopeat overnight in a tub or bucket with a hole in it to wash away salts.

4. Perlite/vermiculite

Perlite is the name of a naturally occurring mineral. A type of volcanic glass, created when the volcanic obsidian glass gets saturated with water over a long time. Natural perlite is dark black or grey colored amorphous glass. For use in gardening, the hard mineral glass needs to be processed into a light, white color, that resembles styrofoam, To complete the transformation, crushed perlite needs to be heated quickly to 900 degrees Celsius.

The process leads to the expansion of the crushed pieces of the mineral between 7 and 16 times their original size and volume, creating that lightweight tiny popcorn.

Advantages of using perlite in your potting mix:

• Perlite retains its shape even when pressed into the soil.
• It has a neutral pH level
• It is non-toxic and natural
• It is super porous and contains pockets of space inside for air. It can retain some amount of water promoting moisture in the mix and while allowing the rest to drain away

Similar to perlite, Vermiculite is a hydrous phyllosilicate mineral that undergoes significant expansion when heated.

Differences between perlite and vermiculite:

• Both are naturally occurring mineral additives that have many of the same qualities.
• Both improve soil quality, especially aiding with aeration.
• Perlite is known to be more effective at aerating soil.
• Vermiculite is better at retaining moisture.
• Perlite is somewhat cheaper than vermiculite.

Neem cake powder

Neem cake is organic manure is a bio product obtained in the process of cold pressing of neem tree fruit and kernels, and the solvent extraction process for neem oil cake.

The AZADIRACHTIN content in neem cake organic manure protects plant roots from various fungi & pests and also works as a soil conditioner. Due to this Neem cakes have been reported to have been (a) antifeedant (b) attractant (c) repellent (d) insecticide (e) nematicide (f) growth disruptor and (g) antimicrobial.

Neem cake manure performs the dual function of both fertilizer and pesticides.

Advantages of using Neem Cake Powder in your potting mix:

• Protects the root from various fungal infections.
• Neem cake improves the organic matter content of the soil, helping improve soil texture, water retention capacity, and soil aeration for better root development.
• Neem cake manure can also reduce alkalinity in the soil by producing organic acids when mixed with the soil hence ensure the fertility of the soil. It’s a great acidity enhancer for plants needing acidic soils.

Bone meal powder

Bone meal is a mixture of finely and coarsely ground animal bones and slaughterhouse waste products. Bone meal is primarily used as a source of phosphorus, calcium, and protein.

As a fertilizer, the N-P-K (Nitrogen-Phosphorus-Potassium) ratio of bone meal can vary greatly, depending on the source. From a low of 3-15-0 to as high as 2-22-0. , though some steamed bone meals have N- P-Ks of 1-13-0.

IMPORTANT: According to recent Colorado State University research, plants can only get phosphorus from bone meal if the soil pH is below 7.0 (acidic soil). That is because in alkaline soil high calcium content will bind to phosphorus and create calcium-phosphate that is unavailable to the plant. Therefore adjusting bone meal quantity for potting mix specific to plants is desirable.

Another thing to note is that while buying bone meal as powder, make sure that it is sterilized/steamed. This is important for proper storage and to avoid the development of fungus on the powder itself.

Mustard cake powder

Like Neem Cake, the mustard cake is also a byproduct obtained from mustard seeds after extracting the oil from the seeds. When mixed as an additive to potting mix, it adds to essential both macro-nutrients and micro-nutrients.

Potting mix recipe example

Here’s my tried and tested potting mix recipe.

• 30% Vermicompost
• 30% Cow Manure
• 20% Cocopeat (Washed)
• 10-15% Perlite/Vermiculite
• 10% Additive (Mix of neem cake powder + bone-meal powder + mustard cake powder)

Mix all the ingredients and if possible put them in a sealed large barrel or bag and leave them to brew for about a week. This is optional but I have experienced that it gives good results.

IMPORTANT: While this recipe works for a large variety of plants I can’t say that it is a universal mix. For example, some plants need more moisture, while some don’t. Adjustment in cocopeat and/or perlite is advisable for particular plants.