For a plant to grow healthily, it isn’t enough for the soil to simply contain sufficient nutrients — those nutrients also need to be available in a form the plant can actually absorb. This is exactly where soil pH comes in.
Soil pH is one of the fundamental properties that affects the solubility of nutrient elements, how they’re held in the soil, and their availability to plant roots. The effectiveness of any fertilization program is closely tied to the soil’s pH conditions.
In other words, a nutrient being present in the soil and a plant being able to make use of that nutrient are not the same thing.
pH refers to the degree of acidity or alkalinity of a medium. Soil pH is generally measured on a scale of 0 to 14:
Below pH 7, soil is acidic
Around pH 7, soil is neutral
Above pH 7, soil is alkaline
The “ideal pH” isn’t the same for every plant. Crop type, soil structure, organic matter content, and growing conditions all shift the optimal pH range. According to the FAO, a soil pH between 6.0–7.5 is generally acceptable for most crops, though some plants thrive below or above that range. pH shouldn’t be evaluated in isolation — it needs to be considered alongside the specific crop’s needs and the soil’s other properties.
The most significant impact of soil pH on plant nutrition is how it changes nutrient availability. Even when an element is present in the soil, without the right pH conditions its solubility can decrease, it can bind with other compounds, or it can shift out of a form roots can take up. This is especially pronounced with phosphorus and several micronutrients.
When soil pH drops too low, it becomes harder for plants to take up certain nutrients. Under low-pH conditions, the availability of calcium, magnesium, potassium, phosphorus, and molybdenum can decrease, while the solubility of iron, manganese, and aluminum can increase.
At very low pH values in particular, the rising solubility of aluminum and manganese carries a toxicity risk for some crops. Turkish Ministry of Agriculture and Forestry sources also note that once pH drops below 5.0–5.5, the solubility of aluminum, iron, and manganese can increase, and high concentrations of these elements can become toxic to certain plants.
As pH rises, the availability of several micronutrients to plants tends to decrease. Under high-pH conditions, the availability of iron, zinc, manganese, and copper can drop — meaning deficiency symptoms can appear in the plant even when these elements are present in the soil.
Phosphorus is also strongly affected by high pH. In alkaline soils, phosphorus reacts with calcium to form compounds the plant can’t easily use. In calcareous, high-pH soils, a nutrition program needs to account not just for how much fertilizer is applied, but how nutrient elements actually behave under those soil conditions — a challenge commonly seen in calcareous farmland across many growing regions, including parts of southern Turkey.
Phosphorus is one of the essential nutrients for plants, playing a role in energy metabolism, root development, and many physiological processes. But phosphorus being present in the soil doesn’t guarantee the plant can actually use it.
At very low pH, phosphorus reacts with iron and aluminum; at high pH, it reacts primarily with calcium — in both cases forming less available compounds. Technical documents published by the Turkish Ministry of Agriculture and Forestry note that plants generally make the best use of phosphorus around pH 6.5. This is why soil pH needs to be factored in when evaluating the effectiveness of phosphorus fertilizer applications.
Iron, zinc, manganese, copper, and boron are micronutrients — needed by plants in smaller quantities, but still critical for development. Reduced availability of iron, zinc, and manganese in high-pH soils is a commonly encountered issue.
For example, a soil may contain plenty of iron, yet high pH can reduce how much of it the plant can actually take up — resulting in iron-deficiency symptoms in the crop.
This points to an important principle: nutrient deficiency doesn’t always mean the nutrient is missing from the soil. Sometimes the issue is that the nutrient simply isn’t in a form the plant can use.
The goal of a fertilization program isn’t just to add nutrients to the soil — it’s to deliver the nutrients a plant needs, at the right time, in a form the plant can actually use. If soil pH isn’t suitable, the fertilizer applied will perform below expectations.
Soil analysis is the starting point for any fertilization program. Alongside pH, other results — organic matter, electrical conductivity, lime content, and macro/micronutrient levels — should be evaluated together. The FAO notes that alongside soil pH, factors like soil texture, organic carbon, and cation exchange capacity are also important when assessing nutrient availability.
A sound nutrition program doesn’t start with “which fertilizer should I use?” It starts with:
What nutrient levels does the crop need?
Are those nutrients actually available for uptake?
How do the soil’s physical and chemical properties affect nutrient uptake?
While soil pH is extremely important, it isn’t the only factor determining plant nutrition. Soil texture, organic matter, moisture, salinity, drainage, lime content, and cation exchange capacity all influence how nutrients behave in the soil and how available they are to plants. Two soils with the same pH can supply very different amounts of nutrients to a crop due to differences in these other properties.
The Right Product at the Right Time
A nutrition program that starts with soil analysis, is planned around the crop’s actual needs, and is applied at the right time forms the foundation of balanced plant growth. But on land where pH-driven nutrient lockup occurs — particularly with iron, zinc, and phosphorus — some of the fertilizer applied to the soil never reaches the plant at all.
At Citsa Tarım, we develop our liquid organic and chemical plant nutrition products, microelement fertilizers, and foliar formulations specifically to help growers work around these pH-related availability issues. If your soil analysis shows iron, zinc, or phosphorus deficiency linked to high pH, foliar application delivers nutrients the roots can’t access directly to the leaf — closing that gap quickly.
Based on your soil analysis results, we can help determine the right product and application program for your operation — check out our product catalog or get in touch with us.
T.C. Ministry of Agriculture and Forestry (Turkey) – Soil Analysis and Interpretation (arastirma.tarimorman.gov.tr)
T.C. Ministry of Agriculture and Forestry (Turkey) – Technical Instructions on Soil and Land Classification Standards
FAO – Global Soil Partnership: Soil Fertility (fao.org)
FAO – Soil Fertility and Crop Production (fao.org)
University of Missouri Extension – Soils, Plant Nutrition and Nutrient Management
University of Missouri Extension – Understanding Your Soil Test Report
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