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How to Read a Soil Analysis Report
Soil & Fertigation · Analysis
How to Read a Soil Analysis Report
A soil analysis report arrives as a page of numbers and units. Most growers glance at it, note whether anything is flagged low, and file it. Read properly, the same page tells you what your soil can supply, what it will lock up, and where your fertilizer budget is being wasted.
Key takeaways
- pH is the first number to read, because it governs the availability of almost everything else.
- Extractable nutrient values depend on the extraction method, so figures from different laboratories are not directly comparable.
- Cation exchange capacity indicates how much nutrient the soil can hold, which shapes how you split applications.
- A report describes supply. Tissue analysis describes uptake. Neither replaces the other.
Start with pH
Soil pH determines the chemical form nutrients take, and therefore whether roots can absorb them. Across Egypt, the Gulf and North Africa most soils sit between 7.5 and 8.5, and at that range iron, zinc, manganese and phosphorus availability all decline sharply.
A pH figure alone does not tell you whether the soil is buffered. A calcareous soil containing free lime will resist acidification; a sandy soil at the same pH may respond to a modest amendment. If the report includes calcium carbonate percentage, read the two together.
Reports sometimes give two pH values, one measured in water and one in a salt solution such as calcium chloride. The salt-based figure is typically a few tenths lower and is more stable across seasons. Check which method your laboratory used before comparing to published thresholds.
Electrical conductivity
EC measures soluble salts. It is reported in dS/m and its interpretation depends on the extraction method, most commonly a saturated paste extract.
A rising EC across seasons is a warning worth acting on before symptoms appear, particularly where irrigation water carries salt and drainage is limited. Salinity management is covered in detail in our article on reading the warning signs of soil salinity.
Organic matter
Organic matter influences water holding capacity, structure, nutrient retention and biological activity. In arid regions, figures below one percent are common, and building them is slow.
The number matters less as an absolute target than as a trend. A soil moving from 0.6 to 0.9 percent over several seasons is improving meaningfully, even though both figures look low against temperate benchmarks.
The macronutrient block
| Element | What the figure represents | What to watch for |
|---|---|---|
| Nitrogen | Usually nitrate or mineral N at time of sampling | Highly mobile and seasonal; a single reading has limited predictive value |
| Phosphorus | Extractable P, method-dependent (Olsen, Bray, Mehlich) | On calcareous soils, extractable P can overstate what the crop can access |
| Potassium | Exchangeable K held on soil colloids | Interpret alongside CEC; sandy soils hold little regardless of the figure |
| Calcium, magnesium | Exchangeable cations | Ratios matter as well as absolute values, especially Ca:Mg |
| Sulphur | Sulphate-S | Mobile like nitrate; deficiency has become more common as deposition declined |
Olsen extraction suits calcareous soils; Bray is intended for acidic to neutral soils and will under-report on high-pH ground. A phosphorus figure without the method beside it cannot be interpreted, and cannot be compared against a figure from a laboratory using a different method.
Cation exchange capacity
CEC measures how many positively charged nutrients the soil can hold against leaching, reported in meq/100g or cmol/kg. Sandy soils are typically low, clays much higher.
The practical consequence is about timing rather than rate. A low-CEC soil cannot hold a large potassium application, so splitting it across the season retains more of it. A higher-CEC soil buffers larger applications. Two soils showing the same potassium figure can therefore need quite different programmes.
Micronutrients
Micronutrient values are usually DTPA-extractable for the metals and hot-water-extractable for boron. On high-pH soils, an adequate reading does not guarantee availability — the element may be present but chemically locked. This is why iron chlorosis appears on soils testing sufficient in iron, as covered in our micronutrients guide.
Turning a soil analysis report into decisions
- Read pH and carbonate first. They set the constraints everything else operates within.
- Check EC against your crop’s tolerance. If it is high, salinity management precedes fertility decisions.
- Note the extraction methods. Without them, the nutrient figures cannot be interpreted or compared.
- Use CEC to decide splitting, not just rate. Low CEC means more frequent, smaller applications.
- Compare against your own history. The trend across seasons on your land is more useful than a single reading against a generic benchmark.
- Confirm with tissue analysis. Soil says what is available; tissue says what the plant actually took up.
What a soil report does not tell you
A report has boundaries, and knowing them prevents decisions it cannot support.
It does not measure availability directly. Extraction methods approximate what a root can access. On calcareous soils the approximation is weakest exactly where it matters most, for phosphorus and the metal micronutrients.
It does not account for the season ahead. Nitrogen mineralises from organic matter at rates driven by temperature and moisture. A report taken in a cool month cannot predict what a hot irrigated season will release.
It does not describe physical constraints. Compaction, a plough pan or poor drainage can limit yield entirely independently of chemistry, and no chemical analysis will show them. A spade and a look at the profile answers questions the laboratory cannot.
It does not identify what the crop actually took up. That is what tissue analysis is for, and the two together give a far more complete picture than either alone.
Building a record over time
The single greatest increase in the value of soil testing comes from consistency rather than from more expensive analysis.
Sample the same zones, at the same depth, at the same point in the season, through the same laboratory. After three or four cycles you have something no single report can provide: a direction. Rising salinity, declining potassium, improving organic matter — these trends drive better decisions than any absolute figure compared against a generic benchmark.
Frequently asked questions
How often should I test?
Annually for intensive systems, every two to three years for extensive ones. Sample at the same point in the season each time, since values shift through the year and comparability depends on consistent timing.
Why do two laboratories give different numbers for the same field?
Different extraction methods produce different figures from identical soil. Neither is wrong. Stay with one laboratory and one method so your results remain comparable over time.
My report says phosphorus is high but the crop shows deficiency. Why?
On calcareous soils, accumulated calcium phosphate can register in the extraction while remaining unavailable to the crop within the season. Placement and timing matter more than rate in that situation.
Does a soil report tell me how much fertilizer to apply?
Not by itself. It tells you what the soil can supply. The rate also depends on the crop, the yield target, the irrigation system and what the previous crop removed.
Send us your soil report
Our agronomy team will interpret the figures against your crop and conditions, and translate them into a practical nutrition programme.
Related reading:
Farming calcareous soils ·
NPK fertilizers explained ·
Crop nutrition
