Understanding Soil pH and Its Impact

Soil pH is a measure of acidity or alkalinity, ranging from 0 to 14, with 7 being neutral. Most crops prefer a pH range between 6.0 and 7.0, though some species have specific preferences. When soil pH drifts too high or too low, nutrient availability shifts, sometimes leading to deficiencies or toxicities.



According to Ask the Plant, "The real work of soil pH is not in an arbitrary number, but in its effect on biological and chemical processes within the soil matrix." Understanding this interaction is key to making informed soil amendments.

Symptoms of Soil pH Imbalance

• Acidic Soils (pH < 6.0): Reduced availability of phosphorus, calcium, and magnesium. Increased solubility of toxic elements like aluminum and manganese.
• Alkaline Soils (pH > 7.5): Reduced availability of iron, manganese, zinc, and phosphorus. Potential buildup of sodium, leading to poor soil structure.
  

Testing and Monitoring Soil pH

Routine soil testing is essential for effective pH management. Regular monitoring allows farmers to adjust inputs proactively rather than reacting to visible nutrient deficiencies. As Walters and Chandler note, "The soil test is not an end in itself, but a tool to understand the deeper story of soil chemistry and biology."

Correcting Acidic Soils

Lime Applications

Applying agricultural lime (calcium carbonate) is the most common method of raising soil pH. The amount required depends on soil texture and buffering capacity.

Other Amendments

• Dolomitic Lime: Provides both calcium and magnesium.
• Wood Ash: A natural, potassium-rich alternative.
• Composted Organic Matter: Enhances biological buffering and pH stability.

Correcting Alkaline Soils

Sulfur-Based Amendments

We recommend bentonite sulfur over elemental sulfur, as it is more active and provides a more efficient pH-lowering effect. Ammonium sulfate and gypsum can also help lower soil pH, making micronutrients more available.



Organic Matter Incorporation

Adding compost, peat, or manure helps acidify soil over time, improving microbial activity and nutrient uptake.

Long-Term pH Management Strategies

• Crop Rotation: Selecting crops suited to current soil pH or those that naturally improve soil conditions.
• Cover Crops: Legumes and deep-rooted plants help mobilize nutrients and buffer pH swings.
• Precision Fertilization: Adjusting nutrient inputs based on actual soil needs rather than applying generic formulas.

Soil pH management is not just about maintaining a number—it’s about creating an optimal environment for plant growth and soil health. By integrating testing, targeted amendments, and biological strategies, farmers can ensure long-term productivity.



As Chandler and Walters emphasize in "Ask the Plant": "Soil health is not static. It is a dynamic, living system that responds to the choices we make season after season." Understanding and managing soil pH is a foundational step toward sustainable, profitable agriculture.