Peut-on faire un profil de sol sans laboratoire ?

Oui, il est possible de réaliser un profil de sol sans laboratoire en prélevant une motte de terre et en effectuant des tests visuels et manuels. Cependant, ce travail ne sera pas aussi précis que des analyses chimiques en laboratoire avec du matériel professionnel.

Que faire si mon sol est très compact ou pauvre ?

Si votre sol est compact vous pouvez le décompacter et l’aérer de manière mécanique avec des outils comme une fourche bêche ou une grelinette. L’apport d’engrais, de compost ou de fumier est aussi favorable pour améliorer la teneur en matières organiques.

Est-ce que le profil de sol remplace l’analyse chimique ?

Non le profil de sol est effectué à l’aide de constatations visuelles mais vous ne connaitrez pas la composition chimique de votre sol. Quatre paramètres chimiques sont recherchés : la texture (sableux, limoneux, argileux ou humifère), le niveau d’acidité (pH), le profil organique et la concentration en minéraux du sol.

Profil de sol

Soil profile: understanding, observing and analyzing the soil structure at depth

Written by: Stanislas Fahy

Published on September 15, 2025

Time to read 10 min

Summary

Soil profile definition

A soil profile is a valuable tool for understanding your soil. It allows you to make various diagnoses of its composition (clay, limestone, humus-rich) and its agronomic quality. By combining this profiling with a soil analysis , you will gain more insight into your soil's fertility level, the plants best suited to its characteristics, and whether or not you need to add amendments or fertilizers.

Why observe the profile of a soil?

Several reasons underlie the implementation of a soil profile:

Soil type: Is your soil sandy, humus-rich, clayey or silty?
Soil composition: the presence or absence of minerals and organic matter (leaves, decomposing branches, remains of small animals, etc.)
Soil health status: Is the soil suitable for agriculture or gardening, or is it depleted?
Indicators of pollution or compaction: Is the soil healthy or polluted by heavy metals , PFAS, or hydrocarbons? Compaction indicates soil damaged by the passage of agricultural machinery. Furrows have been created and have degraded the very structure of the soil, making plant growth more difficult.
Soil profiling can also be a tool for agroecological transition. For example, to move towards more sustainable or biodiversity-friendly agriculture. Or if you want to start a vegetable garden on land that has been intensively farmed or is a former industrial wasteland.

How to create a soil profile?

Spade test method

This spade test method allows you to take a small amount of soil in order to then determine what soil profile it is.

For this, you will need a garden spade. With it, dig out a square block of soil approximately 20 cm wide and deep. As with soil analysis, it can be helpful to take several samples from different areas of your property to get a comprehensive overview.

It is advisable to perform a spade test when the soil is still damp but no longer frost-free, generally from March to May. On dry, frozen, or waterlogged soil, the soil profile analysis will be inaccurate or more difficult.

In certain contexts, such as on a farm or for market gardening, a deeper cross-section (between 1.50 and 3 meters) can be carried out. This gives you access to less superficial layers in which you can easily observe elements such as organic life (earthworms, small animals, etc.) or the density and depth of the root systems of trees and plants.

How to observe a soil profile?

The table below shows you the main elements to observe in a soil profile:

Element to observe	Observation	Analysis
Clod of earth	The soil is porous and not compacted (gamma), it is compacted and cracked (Phy) or compacted without porosity (Delta)	A cracked or compacted root ball will require more work. For example, if the root ball is compacted, it may be necessary to work the soil to a depth of 10 or 20 cm before planting anything.
Load of pebbles	Between 0% and over 30%	The stonier the soil, the harder it will be to grow plants. It is sometimes necessary to remove the largest stones to improve soil aeration.
soil texture	Clayey, silty or sandy	Clay soil is malleable, prone to dirt, and stickiness. It is silty if the soil is powdery, crumbles easily, or has a rough surface. Sandy soil is not very malleable, doesn't easily get dirty, and is granular with visible grains of sand.
Biostructure (this refers to the galleries and worm casts (small mounds of earth) produced by earthworms)	From the absence of galleries and worm casts to the presence of fresh worm casts, galleries, and earthworms	The presence of organic life is a sign of rich soil, favorable to plant growth.
Presence or absence of roots in the soil	The soil has few visible roots, or they are blocked by obstacles. The roots grow in galleries and fissures. Or, a harmonious distribution of roots extending deep into the soil is observed (particularly in trees).	If the soil has few roots, it means the plants won't develop fully. If they are numerous and evenly distributed, it indicates that the soil is favorable to their growth.
Presence or absence of stains	Orange, blue-gray, or black-violet spots. Few spots or none at all.	The presence of colored spots indicates a high iron content and oxidation in the soil. This could be a sign of pollution that will need to be confirmed with a soil analysis.
Odors	Smell of mildew or rot. No odor. Or an earthy smell.	Here too, a rotten smell in the soil can be a sign of pollution. Ideally, the soil should have a pleasant smell, indicating the presence of humus.

The analyses mentioned above are easy to perform without equipment and with the naked eye. You can go further by analyzing the stability of soil aggregates by placing a handful of soil in a large jar filled with water. If the aggregates dissolve, this may indicate unstable soil, susceptible to erosion.

How to recognize the different types of soil?

Texture triangle (clay, silt, sand)

The soil texture triangle is a geometric shape used to classify soils according to their nature. There are both complex and simpler versions. Generally, there are three main soil types: clay, silt, and sand. However, intermediate types and variations exist. For example, you might have a soil that is both silt and clay, or a clay and sandy soil.

The blood sausage test

The sausage test is a manual test. Here's how to perform it:

Take a clod of earth, which you will moisten and knead.
Form a sausage shape approximately one centimeter in diameter.
If it does not become very fine, this means that you are dealing with sandy soil or both sandy and silty soil.
If it does not break, you can consider that your soil is composed of at least 10% clay.
Next, try to form an arc. If the roll breaks, the soil is silty or sandy. If it remains stable, the soil contains at least 15% clay.
Finally, try to draw a circle. If it has cracks, the soil is at least 30% clay. If the surface is smooth, the clay content rises to 50%.

This test provides a useful first step in assessing your soil profile. If you wish to delve deeper, a laboratory particle size analysis is necessary.

Particle size analysis

Particle size analysis allows us to study the size and distribution of soil grains and aggregates. Several analytical techniques are performed in the laboratory: sieving, sedimentation, laser granulometry, etc.

Pouryère offers the Agrokit, a soil agronomic analysis kit. You collect your samples and send them to our COFRAC-accredited laboratory. Once the results are obtained, you can select crops suited to your soil profile, adjust fertilizer application, or increase the profitability of your vegetable garden.

What are the characteristics and advantages of clay, silt, or sandy soil?

Each type of soil has its advantages and disadvantages. Knowing its nature will determine which types of plants are best suited.

Soil type	Benefits	Disadvantages	plants adapted
Clayey	Soil very rich in nutrients	Alkaline soil can prevent plants from accessing the nutrients they need to grow. This type of soil warms up slowly. It becomes sticky when wet and dries out easily in summer.	Vegetables from the cabbage family, fruit trees, or ornamental plants
Silty	Fertile soils with nutrients favorable to growth (except in cases of pollution)	Soil type is difficult to work: this soil compacts quickly	Climbing and perennial plants, grasses, shrubs and trees
Sandy	They warm up quickly after winter and are compatible with early planting. They are less vulnerable to erosion.	Sandy soils often have an acidic pH. Their high permeability prevents nutrients from remaining on the surface.	Tomatoes, melons, squash, strawberries, root vegetables such as potatoes and carrots
Humus	Retains water efficiently. Excellent aeration promotes root development.	Fertilizer is often necessary due to its acidity.	Green salads, root vegetables or berries like blueberries

What indicators can be observed in a soil profile?

Many indicators can be observed within a soil profile.

The composition of the horizons (O, A, B, C)

We consider that there are four horizons in a soil profile:

The O (organic) horizon is the surface layer that contains humus and plant debris, such as decomposing leaves and branches.
The A horizon (arable soil) consists of a mixture of humus and minerals. It is a very fertile layer, often dark in color. It is the playground of burrowing animals such as earthworms, small rodents, and insects.
The B horizon (subsoil) contains a large number of minerals. It is also this layer of soil that plant roots can reach.
Horizon C is the deepest layer, also called fragmented source rock, which overlies the source rock itself.

Organic matter content

Organic matter contains decomposing plants, as well as small dead animals and microorganisms that enrich the soil. Arable land is considered to have at least 5% organic matter (OM), but this can be as high as 20%.

A high organic matter content makes tilling the soil easier and promotes plant growth. It also protects the soil from erosion and retains moisture.

Biological activity (worms, roots, mycorrhizae)

Soil biological activity refers to the presence of bacteria and/or fungi that contribute to its fertility. Examples include earthworms, as well as the density and even distribution of the root system. Mycorrhizae, fungi that form a symbiotic relationship with plant roots, also play a role, enabling them to access phosphorus resources.

Soils damaged by agricultural activities

Some soils can be damaged by the repeated passage of agricultural machinery. This is called a plow pan, which appears as a visible furrow in the soil where vegetation no longer grows. The soil is compacted and quite sterile. Clay soils are more susceptible to this problem.

There are ways to recolonize this space using techniques such as subsoiling or soil drainage. Planting vegetation can also help stabilize the area and make it more fertile.

Who is the purpose of soil profile analysis?

Soil profile analysis is for anyone who wants to know the nature of their soil and be able to improve it if necessary.

Farmers and winegrowers

Farmers and winegrowers are particularly concerned with soil profile analysis. Poor soil or soil with problems will have a significant impact on agricultural yield and productivity. The use of tractors and other agricultural machinery also puts considerable stress on the soil, creating plow pans and compaction.

Gardeners and individuals

If you're a gardener or homeowner with a vegetable garden, soil profile analysis will help you plant the right varieties of plants, depending on the soil type. You'll also know if adding fertilizers and soil amendments is necessary to provide more minerals and improve your soil profile.

Local authorities and urban planners

If you wish to create a shared green space, understanding the soil profile is essential. This is especially true in urban areas where the soil may have had many lives: cultivated land long ago, then fallow, then a built-up area with one or more buildings and subsequent reconstructions. The history of the land is important, particularly if the site is a former industrial wasteland or has been home to potentially polluting activities.

The author of the article: Stanislas FAHY

Stanislas Fahy spent his entire youth in the Dordogne region, exploring its fields, forests, and vineyards. Passionate about nature, he quickly understood that our world must be cherished to preserve its beauty. After studying business, he specialized in sustainable development. Today, as co-founder of Pouryère, he dedicates himself daily to making soil knowledge accessible to everyone.

Frequently Asked Questions about soil profile (FAQ)

Can a soil profile be created without a laboratory?

Yes, it is possible to create a soil profile without a laboratory by taking a soil sample and performing visual and manual tests. However, this work will not be as precise as chemical analyses performed in a laboratory with professional equipment.

What should I do if my soil is very compact or poor?

If your soil is compacted, you can loosen and aerate it mechanically with tools such as a garden fork or broadfork. Adding fertilizer, compost, or manure is also beneficial for improving the organic matter content.

Does soil profiling replace chemical analysis?

No, the soil profile is carried out using visual observations, but you will not know the chemical composition of your soil. Four chemical parameters are sought: texture (sandy, silty, clayey or humus-rich), acidity level (pH), organic profile and mineral concentration of the soil.

Why trust Pouryère for your soil analysis?

Comprehensive support, from sampling to interpretation

Pouryère supports you throughout the entire soil analysis process. Our sampling kits come with a comprehensive guide to walk you through the process. Once you've completed the analysis, simply send us your samples for full analysis and interpretation, which takes approximately ten days.

Solutions for individuals, farmers, communities and businesses

Each soil analysis kit is specialized and pursues a specific purpose:

Agrokit for agronomic soil analysis.
Pollukit for pollutants.
Pestikit for pesticide detection.
PFASkit for PFAS.
Metkit for soil metals.
Solkit for the complete health status of the soil (agronomic analysis, detection of pollutants and metals).
Isdikit is aimed at construction professionals.