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What kind of a Soil?

So you have a pot for your chili seedlings, and now it's time to put them to soil. But what kind of a soil is optimal for them?

If you start looking you'll find a vast number of chili growing articles each having their own little subsection about soils. Not surprisingly the advise is a bit different in each case depending on what writer believes to be correct. Let's delve into the soil question here. I'll cover most of the basics.


The easy way - Potting mixes

Botanical fact: Chilies, potatoes and tomatoes are close relatives. If you want the easy and hussle-free way to grow chilies just go to a gardening store and look for a potting mix for tomatoes or "vegetable growing mix". Most of them will do pretty well. They usually contain a mix of soil, organic matter and fertiliser in all in one.

Many reliable sources recommend using a simple good quality potting mix, added with a bit of compost, coconut coir or other organic materials.

In short, there's two easy choices for chili potting soils: 1. Use a pre-mixed vegetable potting mix 2. Mix organic materials to potting soil yourself

Simple as that!

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Ideal soil nutrient balance and pH

Most pre-made vegetable potting mixes will have a somewhat correct nutrient balance and pH balance. If possible, try to find potting mix that that has N-P-K value of roughly 3-1-2:

(N) Nitrogen

(P) Phosphorus

(K) Potassium

When plants grow they will consume the nutrients from the soil. Heavy growth of foliage and branches will require mainly Nitrogen. Phosphorus and Potassium will be consumed more at the time of flowering and fruiting. Later articles will discuss the quantities and timing of adding fertiliser on the soil.

Key takeaway: When the plant has been put to new soil and it is still small do not add fertilisers! Excessive fertilising will not make the plant grow faster if it already has enough nutrients.

The pH balance refers to acidity level of the soil. Remember when you were at school chemistry class and the teacher had a litmus test? That's it. Chilies and tomatoes prefer a slightly acidic pH between around pH 5.5-7 range. If you are interested you can buy a soil pH meter online to test it yourself. Or buy a litmus test from aquarium store. In Singapore where I live the tap water pH is rather alkaline at pH 7.5-8. This will cause the potting soil to become slightly too alkaline by time. The soil does have a buffering capacity and the pH will shift very slowly. Note that plants will thrive and grow even if the pH isn't optimal. But if you're looking to get the best growth conditions pH will be one factor worth of your attention. In practice pH is a critical success factor only in hydroponic systems. Hydroponics will be discussed in detail in later articles. Read on!

Tip: if you want to retain the most ideal pH balance for potted plants add pH down solution to to the water to bring it to right pH range. You can buy pH solutions in aquarium stores.

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Mixing your own soil mixture

I've done this both ways - mixed my own soils and used the commercial pre-mixed ones. Today I hardly have any opinion on the matter either way. Let's admit, we like it! A gardener has an innate feeling that he must shove his fingers deep in the soil and feel it! Some say that if you don't have some soil under your nails you're hardly a gardener at all!

Most chili growing guides advise mixing some sort of organic matter with the soil to improve its quality. Basically almost any kind of decomposed organic matter can suffice.

Common organic additives are: Peat, compost and coconut coir.

Peat-based additives

Growing peat (not raw peat) is an organic decomposed material that's harvested from drained marches. It's great for germination and growing chilies. It usually has the right pH value around 6 which helps with tomato and chili growth. Some growers feel that this material is the best possible add-on, and some even user it exclusively for their plants. Just bear in mind that when using peat you're using a non-renewable material. Marches and peat will not renew quickly. Luckily there are alternatives that do the job adequately and don't destroy non-renewable nature resources. Read on!

Using compost

You can buy potting compost in bags of different sizes and add it to your soil. The process is pretty simple - add soil and compost to a bag and mix until you reach an even mix. Add roughly one third - to half compost and fill the rest with potting soil.

Perlite and coconut coir

Coconut coir is worth mentioning because it is an alternative to using peat. It's a renewable waste product from coconut industry. Coconut coir holds a lot of water and maintains good aerination in the soil. This can be a way to avoid using so much peat in the soil, and hence, reducing the need to use non-renewable resources.

Some people recommend adding perlite to soil. Perlite is a very light crushed rocky material that can hold large amounts of moisture. Otherwise it is inert and does not affect the plants in any way. People add small amounts to soil to improve moisture retention. Think about it this way - chilies like to have a well drained soil that allows aerination. Adding perlite will allow it to hold more moisture all the way from top to bottom, reducing the need for watering often. Bear in mind that perlite is also a non-renewable material.

Below picture: I'm transplating a Carolina Reaper here to a growing bag. Notice my mistake - I had put leca balls at the bottom of the pot. Later I learned one should never put coarse material to the bottom of pots. (lol). The mix for this plant was 50-50 potting soil and compost. I removed the useless and harmful leca balls. If you look very closely you notice that roots have reached the bottom of the previous pot. It's a good sign because it means the watering has been done right.

Key takeaway: Organic matter improves soil aerination, moisture retention and drainage.

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Drainage, moisture and watering

Chilies like to be watered regularly but sparingly. It is important to let the top soil dry up completely before watering. Some say that slight stressing of the plants will produce hotter peppers. Others say that chilies grow best when there is a constant cycle of wet and dryness.

Let the top soil dry up completely before watering

Pro tip: Lift up the pot before you water it and feel the weight. Then water the pot and feel the weight again. Do this often and you'll learn to directly measure the amount of water in the soil just by lifting up the pot! Don't water until the pot feels light again.

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In accordance to the pot or planter, fill in the soil and let the plant settle. Seedlings or small seeds need light, soilless mix while african violets require soil with some debris (i.e. dead leaves or shredded bard.) Here is a resource from NASA that will help you understand soil in air pollution prevention further.

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