The effect of soil acidity on plants

Soil is the foundation upon which plant life is based, and soil acidity is one of its most important characteristics that determines the fate of agriculture. Soil acidity is like the internal health of the earth, as it affects invisibly but profoundly everything that grows on it. Therefore, this comprehensive article takes you on a scientific and practical journey to explore the world of soil acidity, starting with its scientific definition, passing through the effect of soil acidity on plants, and reaching how to diagnose and treat problems. You will learn how to transform problematic soil into an ideal environment for your plants, and how to recognize the signs of danger before it is too late.

What is soil acidity?

Soil acidity is a measure of the concentration of hydrogen ions (H⁺) in the soil solution and is measured in pH units. The scale ranges from 0 to 14, where if the pH is less than 7 the soil is acidic, if the pH is equal to 7 the soil is neutral, and if the pH is greater than 7 the soil is alkaline. It is also considered one of the crucial factors in the success of agriculture, as soil acidity affects plants and their health.

The difference between acidic, alkaline, and neutral soils

acidic soil

The pH range is < 6.5 and releases toxic amounts of aluminum and manganese at pH less than 5.5. Nitrogen-fixing bacteria such as rhizobia become ineffective, and organic matter decomposes slowly and may contain high concentrations of iron and aluminum.
Common problems in acidic soils include phosphorus deficiency (which combines with iron and aluminum), inhibition of root growth, and reduced effectiveness of pesticides and fertilizers.
The plants that love it are the ideal blueberry: pH 4.5-5.5, rhododendrons, azaleas, conifers, potatoes, and sweet potatoes.

neutral soil

The pH range of 6.5 - 7.5 is the ideal range for most agricultural crops due to the availability of nitrogen, phosphorus and potassium, ideal activity of beneficial bacteria and fungi, and the best root structure and penetration.
It is characterized by a balance of micro and macro elements, rapid decomposition of organic matter, high effectiveness of chemical and organic fertilizers, and high biodiversity in the soil.
Suitable plants in it are almost all vegetables such as tomatoes, peppers, cucumbers and carrots, fruits such as apples, oranges and strawberries, most grains such as wheat, rice and corn and ordinary ornamental plants.

alkaline soil

pH range > 7.5 is often calcareous or sodium-rich, and some elements such as iron, zinc, manganese, and phosphorus are unavailable. Phosphorus combines with calcium to form insoluble calcium phosphate.
Common problems include yellowing of the leaves (chlorosis) due to iron deficiency, poor seed and fruit formation, low soil fertility, and difficulty in absorbing micronutrients.
Suitable plants for it are lavender, rosemary, phlox, carnation, asparagus, spinach, and some trees such as oak and ash.

Soil acidity (pH) is one of the key factors that determine the success or failure of agriculture, as it affects every aspect of plant life, from its ability to absorb nutrients to its resistance to diseases. Some of the mechanisms by which soil acidity affects plants include:

The effect on nutrient availability is because pH determines the solubility of mineral elements in the soil, while at pH 6.5-7.0, most elements are in a balanced and available state.
The effect on soil structure and physical properties: In acidic soil (pH < 5.5), the clay structure is destroyed and a surface crust is formed, while in alkaline soil (pH > 8.0), the soil becomes hardened, the structure deteriorates, and water permeability decreases.
The effect on the activity of microorganisms reduces the decomposition of organic matter and the release of elements from it, thus reducing the natural fertility of the soil.
Direct effects on plant physiology such as root growth cessation, cell membrane damage, black spots on leaves, tissue death, and impaired absorption of calcium and magnesium.
Effects on water and nutrient absorption such as changes in root membrane permeability, osmotic pressure imbalance, and damage to root hairs.
Effects on respiration and photosynthesis, reduced enzyme activity, formation of toxic compounds within the plant, and reduced chlorophyll production.

You may be interested in: Types of agricultural soil conditioners

Plants most affected by soil acidity

Here are some plants most affected by soil acidity:

Plants that prefer acidic soil pH 4.5-6 include blueberries, bilberries, azaleas, rhododendrons, conifers, ferns, potatoes, and sweet potatoes.
Plants that prefer neutral soil pH 6-7.5 include most vegetables such as tomatoes, peppers and cucumbers, fruits such as apples and cherries, and grains such as wheat, barley and corn.
Plants that prefer alkaline soil pH 7.5-8.5 include lavender, rosemary, cauliflower, asparagus, cabbage, and beets.

Causes of soil acidity

Here are some reasons for soil acidity:

Acid rain contains oxides of sulfur and nitrogen.
The decomposition of organic matter produces organic acids.
Use nitrogen fertilizers, especially ammonium sulfate.
Irrigation with hard water containing mineral salts.
The activity of plant roots secretes organic acids.
Acidic parent rocks such as granite.

Signs of high soil acidity in plants

High soil acidity (low pH) negatively affects most plants. Here are the visible signs on different parts of the plant that are due to the effect of soil acidity on plants:

Symptoms on the roots

Stunted and stunted growth of roots, few and short lateral roots, thick and short roots with irregular branching and a dark brown or black color, especially at the tips, damage to root hairs and a severe decrease in their number, lack of deep penetration and roots remaining in the surface layer, and root rot in severe cases (pH < 4.5).

Symptoms on the leaves

Yellowing of most leaves and chlorosis between the veins in the yellow areas between the green veins, magnesium deficiency such as yellowing starting from the lower leaves, calcium deficiency and yellowing of the edges of small leaves and leaf spotting, whether small brown or black spots.

Leaf deformities

Curling of young leaves, especially at the growing tips, stunted leaf size, smaller than usual leaves, abnormal leaf thickness where they are thick and leathery to the touch, irregular shape, and wavy or twisted edges.

Symptoms on stems and branches

The main stem is stunted, short in stature compared to age, weak stem thickness, thin and weak stems, reddish-brown color on the stems in some species, death of terminal buds, cessation of longitudinal growth, lack of lateral branching, and sparsely branched plants.

Symptoms on flowers and fruits

Delayed or failed flowering, low flower production, early flower drop before pollination, poor fruit set, low number of fruits, stunted fruit size, deteriorating fruit quality, sour taste or poor texture, and distorted or irregular fruit shapes.

How to accurately measure soil acidity

Digital pH meters provide accurate and fast readings.
pH test strips are an easy and low-cost method.
Chemical test kits and the use of reagent solutions.
Agricultural laboratories provide detailed and accurate results.
Home methods include mixing soil with water and baking powder or vinegar, and observing natural indicator plants.

Treating soil acidity effectively

Here are some ways to treat soil acidity:

To raise soil acidity, adding agricultural sulfur is the most effective method, or using ammonium sulfate fertilizer and adding acidic organic materials such as pine sawdust or oak leaves, and irrigating with water containing diluted apple cider vinegar.
To reduce soil acidity, agricultural lime or calcium carbonate, wood ash (a natural source of alkali), dolomite (calcium and magnesium carbonate), ground eggshells (a source of calcium), or bicarbonates (for mild cases) are added.

The role of the student store in addressing soil acidity problems

The Student Store offers many solutions such as providing pH measuring devices at affordable prices for students and farmers, providing free consultations on improving soil properties, providing appropriate treatments such as agricultural lime and sulfur, training workshops on soil management, and providing plants adapted to different pH levels.

conclusion

From what we have reviewed, it is clear that managing the effect of soil acidity on plants is both a science and an art. It is a science in measurement and analysis, and an art in observation and adaptation to nature. There is no absolutely bad soil, but rather soil that is unsuitable for the cultivated plant. With a simple and well-thought-out modification, the soil can be transformed from an obstacle into a strong ally for growth. You can contact Al-Talib Store for soil acidity care and investment in plant and human health via the social networking site WhatsApp.

Frequently Asked Questions

What is the ideal pH level for most plants?

Most plants prefer soil with a pH between 6 and 7, where nutrient availability is at its best.

How often should soil acidity be measured?

It is recommended to measure soil pH at least once a year, preferably before the start of each new growing season.

Is it possible to permanently modify soil acidity?

No, adjusting soil acidity requires continuous monitoring because the soil tends to return to its original state over time.

What is the difference between agricultural lime and dolomite?

Agricultural lime is a source of calcium only, while dolomite is a source of both calcium and magnesium.

Can plants be grown in soil that is unsuitable due to its acidity?

Yes, but on the condition that the soil is modified, or special pots and soil are used, or tolerant varieties are chosen.