Determine soil types: loam soil, clay soil & Co.

Sometimes it is important to know what type or type of soil you have in your own garden. But what types of soil are there anyway? The soil can be tested and determined with a finger test.

Do you have “good soil”? Many - especially freshly baked - garden owners can hardly answer this question, or only with great uncertainty. From hearsay you know what soil is in the area. But what if someone else's land was once distributed on your own property? And is what the neighbors say is true?
You can find out what type of soil you have with our quick guide to checking soil type. This enables you to see how comfortable certain plants or even the lawn feel on your soil.

What types of soil are there?

Soils are made from very different raw materials, i.e. rocks, and have been shaped over thousands of years. Weather, temperatures, water movement and the entry of rock dust and organic materials left their traces. Each floor is unique due to its individual history. Nevertheless, for the comparability of soils it is important to subdivide them - into soil types.

The soil types are based on the different grain sizes that occur in a soil. So they reflect how many very small, medium-sized or very large particles make up the soil. Soil particles can be far less than a micrometer or over 20 cm in size.
The many different grain sizes are summarized in fractions, i.e. groups with similar grain size, and called sand, silt and clay. Sand is the coarsest grain size, silt is medium-sized and clay is the finest grain size. The type of soil depends on the ratio in which these three soil components are mixed. The soil type triangle is a useful tool for visualizing this.

Tip: Clay is not a separate grain size fraction. Soils are called loam, which combine all three grain sizes in similar proportions. So loam consists - roughly speaking - of sand, silt and clay in similar proportions. They are considered particularly fertile soils. In contrast, soils that consist primarily of one grain size are rated as unfavorable for plant growth.

Sandy soil

Sands can be found in the soil type triangle in the bottom left corner. Soils with a high proportion of sand are very water-permeable due to their primarily coarse grain size, so they can hardly store any water. However, waterlogging almost never occurs on such floors.

Sandy soils are very well ventilated, and oxygen can penetrate well between the coarse grains of sand. Plant roots can very easily take root in sandy soils and air-breathing microorganisms also feel extremely comfortable here. Due to the very active microorganisms, organic residues in the soil are quickly broken down, but unfortunately there is hardly any humus. Due to the mostly low humus content, on the other hand, sandy soils can hardly store nutrients and are generally considered to be poor in nutrients.
Sandy soils are easy to work on because the sand does not stick to each other or to garden tools. In addition, it does not become heavy when it rains, because it hardly absorbs any water. When speaking of light soils, sandy soils are always meant.

Sandy soils have an unstable pH value and can be easily influenced by lime and acids.
The sands include the pure sands, loam sands and silt sands. Very sandy soils can be found in Germany, for example, in the Lüneburg Heath and the entire Heidekreis, where they emerged from the terminal moraine of the glaciers of the last Ice Age.

By the way: Because of their low storage capacity, sandy soils have to be fertilized and watered regularly, but in small doses.

Silt soil

Silts are drawn in at the top of the soil type triangle. Due to its mean grain size, silt lies in the middle between clay and sand in terms of its properties. The pore size of silt is particularly good for plant growth: the spaces between the individual soil particles are of a size that absorbs water well, similar to a sponge. But because the pores are not too small, they release the water without much resistance, for example when plant roots create a negative pressure to absorb water. For this reason, silt soils are often particularly good locations for plants and develop into the most fertile fields, meadows and natural landscapes. Similar to clay soils, silt soils provide a satisfactory habitat for microorganisms and also tend to build up a lot of humus. As a result, silt soils are good stores of nutrients and water that are very loose and easy to work with.

The silts include the sand silts, clay silts, and clay silts.
Fertile clay silts can be found, for example, in the foothills of the Alps around Memmingen in Bavaria.

By the way: Unfortunately, silt is at risk of being blown away in drought due to its low level of adhesion. A silt soil should therefore always be planted and never lie fallow.

Clay soil

Clays can be found in the soil type triangle at the bottom right. Clay particles are the smallest grain fraction that occurs in soils. Anything smaller than 0.002 mm is considered clay. Due to its small grain size, clay only has tiny pores between the particles that bind a lot of water. However, the water will hold onto it so strongly that most plants can hardly use it. Clay minerals are able to shrink and swell. When they have soaked up water, there is hardly any air left in clayey soil. So there is hardly any soil ventilation on clayey soils, which many plants and microorganisms cannot tolerate well.
In addition to water, clay minerals can also store some nutrients very well and are therefore often rich in nutrients. Because clay soaks up so much water, then sticks to one another, and when dry it becomes extremely hard as a result of shrinking, it is difficult to work with. When we talk about heavy soils, we mean clay-rich soil.
Soils that are too clay inhibit the formation of humus, because pure clay soil is too hostile to life for microorganisms and other soil organisms. A good proportion of clay in the soil can also stabilize humus, because clay minerals are also formed Humus molecules so-called "clay-humus complexes", which are very difficult to break down and the soil extremely make fertile.

Clay soils have a very stable pH value and are only very slowly influenced by lime or acids. The clay soils include the silt clays and the loam clays.
Silt clays, for example, can be found over a large area on both sides of the Elbe all the way from the North Sea to Hamburg - no wonder that fruit growing is flourishing there, because many fruit trees love clayey ones Floors.

By the way: Clay can store a lot of water, but plants cannot necessarily use this water. In order to be able to grow different plants, heavy clay soil often has to be mixed with sand. If plants are to be grown in clay, it is particularly important to ensure that humus is built up or to use high-quality potting soil and compost.

Clay soil

Loams are in the center of the soil type triangle. They're a good mix of silt, sand, and clay. Their properties are considered to be particularly favorable for many plants, because they have everything “im Mediocre “: They store a moderate amount of water, a high proportion of which is also good for plants to use is. They offer with the help of the correct humus management a high potential to build up a lot of fertile humus. In their clay content and also in the humus, loam soils can store a lot of nutrients and a lot of moisture and are therefore usually rich in nutrients. Good floor aeration is also guaranteed with a sand content of at least 30%.
However, clay soils can be difficult to work with due to their ability to store a lot of water and cement together firmly.

The clay loam includes sand loam, normal loam and clay loam.
Normal loam can be found, for example, in the Swabian-Bavarian old moraine landscape around Munich, and enable flourishing agriculture there.

Tip:Difference between soil types and soil types
The terms soil type and soil type are often used synonymously. The soil type only describes the topsoil, i.e. the part of the soil with the most roots. The soil type, on the other hand, contains a large amount of additional information, specifically on "soil genesis", i.e. the formation of the soil. Alien-sounding names such as Rigosol, Gley, Anmoorgley, Pseudogley, Parabraunerde, Reduktosol, Ranker or even black earth include the basic material of the soil for soil scientists. They also provide information about its state of development and thus its age and the soil horizons it contains.

Determine soil type: finger test on the soil

The finger test is a simple and amazingly reliable way to determine the type of soil. The more different floors you have in your hands, the more reliable the assessment will be. In order to be able to interpret the finger test, one must be aware of the properties of the 3 grain sizes:

• sand feels grainy, rough, and scratchy. It does not stick in the finger grooves.
• Silt feels velvety floury and is hardly cohesive. If you smear silt, the smeared surface won't shine. Silt adheres strongly to the finger grooves.
• volume feels sticky and is strongly cohesive. That is why it is easy to shape. If you smear clay, it makes a shiny smeared surface.

Carrying out a finger test: step-by-step instructions

• Take soil sample: For this purpose, take samples distributed over the entire examined area. Soil from a depth of 5 to 20 cm is suitable for the sample. For each sample, discard the top 5 cm, as it could be too heavily contaminated with organic material and plant residues. Mix all samples well in a bucket.

• Set humidity: The mixed sample should have a medium moisture content, i.e. neither wet nor dry. One speaks of “culture moisture” because the water content looks as if it were just right for plants. Spread soil that is too wet and let it dry a little, dampen soil slightly with a spray bottle if it is dry.

• Sample 1 - roll sample: For this purpose, a walnut-sized part of the sample is first kneaded firmly in the hand. Then it is rolled out on the palm of your hand like putty into a roll the thickness of a pencil.

observation	interpretation
Sample cannot be rolled out at all	The base of the soil is sand
The sample can only be rolled out once; it crumbles when it is rolled out repeatedly	The basis of the soil is silt
Sample can be rolled out and kneaded repeatedly	The basis of the soil is clay

• Sample 2 - rub sample: A handful of the sample is examined for this purpose.

test	observation	interpretation
Rub the sample between your fingers	Above all, the floor feels rough / scratchy	High proportion of sand
Above all, the floor feels velvety	High proportion of silt
Above all, floor feels greasy	High tone content
Floor feels indefinably both grainy and greasy and velvety	Mixed soil / clay soil

• Sample 3 - visual comparison and adhesion test: A handful of the sample is examined for this purpose.

test	observation	interpretation
Look at the sample, move it in your hand	Visible single grains	Contain sand
Fine dust sticks in the finger grooves	Contain silt
Ground is very dark	Contains a relatively large amount of humus

The finger test is prone to errors in certain cases:

• Samples too dry are estimated to be grainier / sandy
• Samples too moist are estimated to be more cohesive / clayey
• Very humus soils are incorrectly assessed because humus "mediates" both light and heavy soils: clay and sand contents are then estimated too low and silt contents are estimated higher.

If you don't trust yourself to assess the type of soil or need more information about your own garden soil, Specialized laboratories such as the Raiffeisen Laboratory Service offer a good, but of course not free Alternative. In addition to the type of soil, a soil analysis also determines the pH value and the content of some nutrients.

Humus may interfere with the soil analysis a little, but it serves as a nutrient and water store in soils and loosens the structure so that plant roots grow better. It is food for soil organisms and a crucial component of fertile soils. Every type of soil is improved by increasing the amount of humus - reason enough, ours Instructions for correct humus management to use to increase the humus content of your own garden soil!