Understanding Soil pH and Its Impact on Agriculture

Soil is the living foundation of farming. Every seed you sow depends on the soil to provide water, nutrients, and a medium to grow. But did you know that even if your soil has enough nutrients, plants may still fail to absorb them if the soil pH is not balanced?

Soil pH is one of the most overlooked aspects of farming, yet it plays a vital role in nutrient availability, microbial activity, crop selection, and fertilizer efficiency. By understanding and managing soil pH, farmers can improve crop productivity and reduce unnecessary input costs.

What is Soil pH?

Soil pH is a measure of how acidic or alkaline the soil is, expressed on a scale of 0 to 14:

• pH 7.0 = Neutral soil
• pH below 7.0 = Acidic soil (lower the value, stronger the acidity)
• pH above 7.0 = Alkaline soil (higher the value, stronger the alkalinity)

Most agricultural crops prefer soils that are slightly acidic to neutral (pH 6.0–7.5). But not all crops are the same—blueberries and tea prefer acidic soils, while barley and cabbage prefer neutral to slightly alkaline soils.

👉 Example: If you grow paddy in acidic soil, it may still perform well. But if you grow groundnut in the same soil, nutrient deficiency may occur.

Why Soil pH Matters in Agriculture?

Soil pH is more than just a number—it controls the soil’s chemical, physical, and biological processes. Here’s why it’s so important:

1. Nutrient Availability

• Nutrients dissolve in soil water and become available for plants. But extreme pH levels can “lock” nutrients.
• Example: In acidic soils (pH < 5.5), phosphorus becomes unavailable, while aluminum and manganese may become toxic.
• In alkaline soils (pH > 7.5), micronutrients like zinc, iron, and manganese are not available, leading to deficiencies even if fertilizers are applied.

2. Microbial Activity

• Beneficial microbes that fix nitrogen, decompose organic matter, and improve soil health work best in neutral soils.
• Too much acidity or alkalinity slows down microbial activity, affecting soil fertility.

3. Crop Suitability

Crops have different pH preferences.

• Acid-loving crops: Tea, coffee, potato, pineapple.
• Neutral pH crops: Wheat, rice, maize, vegetables.
• Alkaline-tolerant crops: Barley, cotton, spinach.

4. Fertilizer Efficiency

• Fertilizers work effectively only within certain pH ranges.
• Example: Urea applied to highly alkaline soil may release ammonia gas and get wasted. Similarly, phosphorus fertilizers are useless in highly acidic soil.

Common Soil pH Problems in Indian Agriculture

Acidic Soils (pH < 6.0)

• Found mostly in high rainfall regions like Assam, Kerala, Odisha, Jharkhand.
• Problems: Low phosphorus availability, calcium and magnesium deficiency, aluminum toxicity.

Alkaline/Saline Soils (pH > 7.5)

• Found in arid and semi-arid regions like Rajasthan, Gujarat, parts of Telangana and Maharashtra.
• Problems: Hard soil structure, low micronutrients (iron, zinc, manganese), poor water infiltration.

How to Manage Soil pH?

Farmers can take corrective actions to balance soil pH.

For Acidic Soils

• Apply Lime: Use agricultural lime (CaCO₃) or dolomite to neutralize acidity.
• Crop Selection: Choose acid-tolerant crops like tea, rice, potato.
• Organic Manures: Continuous use of compost and green manure reduces soil acidity over time.

For Alkaline Soils

• Apply Gypsum: Helps reduce sodium and improve soil structure.
• Organic Amendments: Compost, FYM, and green manures release organic acids, improving soil balance.
• Microbial Biofertilizers: Some microbes tolerate alkalinity and improve nutrient availability.
• Crop Selection: Grow tolerant crops like barley, cotton, pearl millet.

General Tips

• Regular Soil Testing: At least once every 1–2 years to monitor pH and nutrient status.
• Balanced Fertilization: Avoid overuse of chemical fertilizers, which can alter soil pH.
• Integrated Soil Management: Combine organic, inorganic, and biological inputs for long-term soil health.

Key Takeaways for Farmers

• Soil pH directly impacts nutrient uptake, crop yield, and fertilizer efficiency.
• Most crops thrive in pH 6.0–7.5, but some crops have special preferences.
• Acidic soils require liming, while alkaline soils benefit from gypsum and organic matter.
• Regular soil testing and adopting corrective measures ensure healthy soil = healthy crops = higher profits.