Soil testing

What’s in the Soil?

In my research I read a lot about types of soil. Just looking at the soil in my garden it was clear that it was not rich and dark humus but chalky-pale, powdery and depleted clay. I didn’t think I needed a scientific soil test to tell me what was in it because there was probably nothing much of anything left in it. So I researched some do-it-yourself quickie tests:

  1. Sausage Roll Test

Dampen soil with a little water so it becomes malleable. Try to roll a sausage, take the end between your fingers and let it hang down.
If you can’t form a sausage at all, you have sandy soil. If the sausage breaks apart, it has about 25-50% clay in it. If it does not break at all, it’s clay soil.

2. Vinegar / Soda Test

Mix some soil from your garden and put it into two different containers. Pour some vinegar onto the first sample. If you see white foam, the soil is alcaline. Mix the second sample with some water to make a mud mixture and sprinkle it with baking soda. If you hear a little fizzing sound or see bubbling, the soil is acidic. If nothing happens, the soil is neutral.

2. Jar Test

Combine some soil samples from different areas of the garden, about 20cm deep. Mix it up, take out larger stones or wood chips, and fill it into a tall glass container or jar. Add clear water to fill the jar about three-quarters full, then add about a teaspoon of liquid dish soap. Close the jar well, shake it thoroughly, then let it sit for at least 24 hours. If your soil contains heavy clay, leave the jar for 48 hours – until the water at the top has cleared.

How to read the results:

Sand has the largest and heaviest particles and will collect on the bottom. Above the sand will be the silt particles, and the fine clay will be at the very top.

Sandy soil: relatively large particles sink and collect rapidly at the bottom and the water will become clear quickly.
Clay soil: water remains cloudy and there is only a thin layer of larger particles at the bottom. Silty soils may also mimic this result.
Peaty soil: lots of debris on the surface with only a small amount of sediment on the bottom.
Chalky soil: a layer of white gritty particles on the bottom and pale gray water.
Loamy soil: clearly visible layers of sediment and clear water at the top.

Types of Soil

Sandy soil is usually medium-brown in color and crumbly. It absorbs water quickly but does not retain it or nutrients well. That’s just fine for many drought-resistant plants needing poor, well-drained soil. It heats up quickly in spring and is easy to work. In French it would be called “sol sableux”.

Silt soil is light and fertile. It is soft and powdery to the touch and greyish-brown in color. It drains well but also retains enough moisture. In French this type of soil is called “limoneux”.

Clay soil is usually dark brown and fertile. It is sticky to the touch when wet and hard when dry. Heavy rains cause puddles because it does not absorb water quickly and when wet, it tends to stay wet – causing problems with plants whose roots are sensitive to continuous humidity. It is slow to warm up in spring and hard to work. In French it is called “argileux”.

The ideal soil for most plants consists of 40% sand, 40% silt, and only 20% clay and is known as “loam”. It is a fertile and balanced mixture that drains well, but also holds water sufficiently well.


Peaty soil is usually dark because it is very organic and moist to the touch because it holds water. It is not really rich in nutrients and it is acidic. It works well for a lot of plants whose ancestors grew in moist woods and swamps. In French peaty soil is called “bruyère” or “sol acide”.

Chalky soil is usually light colored. It has a fine concistency when dry, can be sticky when wet. It drains well, which means it does not hold water and dries out quickly. It is alkaline and also does not hold nutrients well. In French it would be called “alcalin”, “basique” or “sol calcaire”.

In France, one distinguishes

– bruyère/acide = for plants who need peaty, acidic soil
– calcaire = for plants who need chalky, alcaline soil
– neutre = for plants that need balanced PH
– tous = for plants that will grow in any soil

Types of soil:
– argileux et lourd = heavy, water-retaining clay soil
– argilo-calcaire = heavy, alcaline clay soil
– argilo-limoneux = rich and light clay-silt soil
– calcaire = poor, draining and alcaline soil
– sableux / caillouteux = poor and draining soil consisting of sand or gravel

What does it mean for my garden?

I’m not really sure. The consistency of the soft top layer seems to indicate silt, which would be good – but unlikely unfortunately. It is much lighter in color and it does not absorb large amounts of water quickly – instead it sticks together so that puddles form. And at about 40-50cm deep comes rockhard clay where a spade doesn’t even make a dent and you need a pickaxe to dig. So all that would indicate chalky and alcaline soil, that I will mix with organic material, gravel and coarse sand to improve its texture and drainage.


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