What is the importance of soil analysis?
Every farmer dreams of fertile, productive soil and high yields.
Unfortunately, most Polish soils are deficient in essential nutrients, which means their levels need to be replenished.
But that’s not all : the majority of soils are also too acidic, so without proper correction, no fertilization method will be truly effective.
That is why specialists emphasize one key principle: before applying fertilizer, test your soil to find out what actually needs to be improved.
Regular soil analysis is the foundation of informed, modern agriculture. It makes it possible to assess soil condition (pH, nutrient content, humus level), which directly translates into precise fertilization planning. As a result, farmers can achieve high yields while avoiding wasted fertilizers (and money!).
Important! Fertilizing “by eye” is not only ineffective, but can also lead to yield losses and harm the natural environment.
So how should soil analysis be approached? We’ll explain it step by step — from proper sampling methods, through result interpretation, to implementing the right corrective actions.
Soil sampling step by step
- When should samples be taken? In autumn, after harvest, or in spring — but before fertilization.
- When should samples NOT be taken? After heavy rainfall or snowmelt, and during drought. Extreme weather conditions can distort test results.
- How often? The absolute minimum is once every 4 years for each field.However, experience shows that annual analyses are the most valuable — they allow fertilization plans to be adjusted to the current season (not the previous one).
• Remember: the more up-to-date the data, the more accurate the fertilization decisions.
1.Prepare the equipment
You will need:
- An Egner soil sampler (soil probe) or a narrow spade,
- A plastic bucket (not metal),
- Plastic zip-lock bags or special containers provided by the laboratory,
- A marker for labeling the samples.
Important! If you want reliable results, all tools and containers must be clean — free from soil residues and fertilizer remains.
2.Select a representative field area
One composite sample should represent a maximum of about 4 hectares of a field. If your field is large or diverse, divide it into relatively uniform areas (consider factors such as soil type, cropping and fertilization history, and yield level). Non-representative areas include field margins, places where stacks or manure piles were located, and visibly degraded zones. These areas can be analyzed separately to identify the causes of degradation and apply an individual “remedial plan.”
3.Take individual samples from the designated area
Important! Samples should be taken from 15–20 locations. Move across the selected area in a zigzag pattern or along a diagonal so that the sampling points form an X, W, or S shape.
Remove about 2 cm of the top layer (mulch, turf, crop residues).
Take soil from the topsoil layer (about 20 cm for arable land, about 10 cm for meadows and pastures).
- Egner soil sampler (soil probe): Insert vertically, rotate 90°, remove, and place the sample into the composite container (bucket).
- Shovel: Insert vertically, cut a thin slice of the exposure from the side (width 5-7 cm, thickness 2-3 cm) and throw it into the collective sample container.
4.Mix the collective sample.
After collecting all individual samples, thoroughly mix the contents of the bucket to obtain a uniform composite sample.
Weigh out 0.5 kg (approximately 0.5 liters by volume) and transfer it into the prepared bag or the container provided by the laboratory.
5.Label the sample and deliver it to the laboratory
Use a permanent marker to write:
- Your full name or farm name,
- Sampling date,
- Field number or plot name,
- Soil layer (e.g. 0–20 cm).
Important!It is best to deliver the sample to the laboratory on the same day. If this is not possible, store it in a cool, shaded place. Before testing, it’s also worth checking whether the selected laboratory has any specific sampling requirements (this information is often available on its website).
Where should the sample be delivered? To one of the accredited laboratories, i.e. facilities that have passed formal inspections and received the appropriate certification (most often from the Polish Centre for Accreditation – PCA):
-The nearest Regional Chemical and Agricultural Station, operating under the Central Laboratory for Soil and Fertilizer Testing,
- Research units of agricultural universities, such as the Institute of Soil Science and Plant Cultivation in Puławy or Universities of Life Sciences (Poznań, Lublin, Wrocław, etc.),
- Commercial laboratories (often offering sample collection and result interpretation services).
The waiting time for results depends on the laboratory — usually ranging from a few days to several weeks.
Important! To ensure result comparability, it is recommended to regularly submit samples to the same laboratory. This way, you can be confident that changes in soil parameters reflect real soil conditions rather than differences in testing methodology.
Key soil fertility parameters and interpretation of results
A soil analysis report contains parameters that describe soil fertility. The most important ones include soil pH, the content of basic macronutrients (phosphorus, potassium, magnesium, sometimes calcium and nitrogen), selected micronutrients (e.g. boron, copper, zinc, manganese), and often the humus (organic matter) content.
At first glance, interpreting these numbers may seem difficult, but in practice it comes down to determining:
- What the soil is lacking,
- What is within the optimal range,
- And what may be present in excess.
pH (soil reaction)
This is the first parameter to look at when analyzing soil test results. Soil pH determines the availability of most nutrients to plants and the proper development of the root system. The optimal pH range is approximately 6–7 (slightly acidic to neutral). There is a high probability that your soil falls into the “acidic” or “very acidic” category — like nearly every second field in Poland — with pH values below 5.5 or between 5.6 and 6.5.
Important! Excessively acidic soil (low pH) limits the uptake of macro- and micronutrients and can even lead to soil degradation. That is why it requires proper correction (liming; more details in e-book 2). Strongly acidified soils become compacted and cold, manage water less efficiently, and generally lose their productivity.
Macro- and micronutrients
Macro- and micronutrients:
- Phosphorus (P),
- Potassium (K),
- Magnesium (Mg),
- Nitrogen (N).
Important! Each of these elements plays a very important (and different) role in plant nutrition, and their deficiency limits yields. For example, phosphorus and potassium are responsible for growth energy, flowering, and plant water management, while magnesium is essential for photosynthesis (it is a component of chlorophyll, the green plant pigment).
Standard soil analyses usually determine the content of P, K, and Mg, because nitrogen (N) levels are highly variable. Nitrogen tests are carried out on special request and often at greater depths (e.g. 30–60 cm).
If your soil shows “low” or “very low” levels of P, K, or Mg, it means that without replenishing these nutrients, plants are unlikely to develop properly. On the other hand, “high” or “very high” levels indicate that the soil contains sufficient amounts of a given element. In practice, many Polish soils are deficient in phosphorus and potassium — elements crucial for growth energy, flowering, and plant water management.
Micronutrients include, among others:
- Boron (B),
- Copper (C),
- Zinc (Zn),
- Manganese (Mn),
- Iron (Fe),
- Molybdenum (Mo).
Plants need these elements in much smaller quantities than macronutrients, but they are still essential. Many soils in Poland are particularly deficient in boron and copper. Boron deficiency may cause inhibited root growth and poor seed setting (especially important in crops such as rapeseed, sugar beets, and root vegetables), while copper deficiency negatively affects cereals (grain quality deteriorates and plants become more susceptible to diseases). Excesses of micronutrients are rare, but on very alkaline soils the availability of zinc or iron may be limited, which is visible as yellowing of young leaves.
Important! A “low” or “very low” level of a given nutrient requires supplementation through fertilization, while a “high” or “very high” level allows — and even necessitates — reducing fertilization to avoid nutrient accumulation (and to save on fertilizer costs).
Humus content
Humus (expressed as the percentage of organic carbon or humus) indicates soil fertility in the long term (more in Chapter 2). Polish arable soils often contain only 1–2% humus, which is considered a low level — ideally, it should be above 3%..
Important! If the analysis shows a low level of organic matter, the soil lacks “life.” In such cases, it is worth considering practices that increase humus content, such as applying manure, compost, or growing cover crops. A high organic matter content, on the other hand, indicates good biological soil condition — but it still requires care to prevent humus loss (e.g. through erosion or excessive ploughing).
Soil balance indicators
Some laboratories also provide soil balance indicators,,which help assess the proportions between individual components, such as the ratios of:
- C:N(carbon to nitrogen) – optimally around 10:1, indicating the rate of organic matter decomposition,
- Ca:Mg (calcium to magnesium) – should be in the range of 5:1 to 7:1. A ratio that is too low (excess magnesium relative to calcium) may indicate compacted, heavy soil, while a ratio that is too high may signal magnesium deficiency for plants,
- S:N (sulfur to nitrogen) – ideally about 1:10. When sulfur is deficient, plants are unable to use supplied nitrogen efficiently.
Important! Interpreting soil analysis results means identifying limiting factors — the weak points of your field. Test reports often include recommendations (e.g. whether liming is required or suggested fertilizer rates for a specific yield), which should be treated as a solid basis for further action.
What should you do with soil analysis results?
Soil analysis results should never be filed away and forgotten — they form the foundation of all further actions. Once you know which parameters deviate from the optimum, it’s time to create a plan to improve soil fertility and meet crop requirements. This is done in two parallel steps:
1. Take corrective actions for the soil,
2. Plan fertilization (nutrient supply).
Important! Correct first, then fertilize.
Soil corrective actions
The goal is to restore chemical, biological, and physical balance in the soil..
- pH too low. Liming is absolutely essential. Strongly acidic soils cannot be made fertile without correcting soil reaction. The type of lime (e.g. calcium or magnesium lime) should be selected according to soil type, while the application rate depends on the agronomic soil category and current pH. Detailed lime rate tables are available in recommendations from chemical–agricultural stations and agricultural literature (more in e-book 2). Raising soil pH improves soil structure and releases nutrients that were previously unavailable — effects are often visible already in the next harvest.
- Humus content too low. It is worth implementing practices that increase organic matter levels, such as organic fertilizers, green manure (cover crops), and proper management of crop residues (more in Chapter 2). These measures — sometimes referred to as agricultural biologization — improve soil structure, activate beneficial microorganisms, and naturally enhance soil fertility. These are long-term actions, but they pay off with better soil quality and stable yields.
Only very rarely do Polish soils require other types of correction, such as leaching (in the case of excessive salinity), remediation of heavy metal contamination, or reduction of excessive concentrations of certain elements. In such cases, expert consultation is essential.
Fertilization planning
The goal here is to meet the current nutritional needs of crops in a given season.
Important! When interpreting nutrient levels, the “bottleneck rule” applies: the element present in the smallest amount is usually the one that most strongly limits yield. Therefore, the aim should be to balance the levels of all key macro- and micronutriens.
Using soil analysis results, you can develop a balanced fertilization plan that compensates for deficiencies without duplicating nutrients already present in the soil (more in e-book 2). The general rule is simple: adjust mineral fertilizer rates to supplement missing nutrients up to the level required by the planned crop.
- On the one hand, such a plan allows fertilizer rates t,o be reduced, which means cost savings and a lower risk of soil and water pollution.
- On the other hand, directing higher inputs where the soil is poor quickly delivers results in the form of higher yields.
The ultimate goal is to bring the soil to a state where no clear limiting factors restrict plant growth, and fertilization serves to maintain fertility while covering the crop’s current nutrient demand. Remember — working with soil based on data is a professional approach that helps avoid mistakes and allows you to fully unlock the potential of your land.
