At Agresol, managing soil pH is a top priority for improving plant and soil health. For many farmers, acidity is a silent yield killer, limiting mineral availability and stunting root growth. This guide explores the root causes of soil acidity and the regenerative strategies we use to restore balance.
First, watch the video below from our Youtube channel Agresol (and make sure to subscribe!)
What is Soil Acidity?
Soil acidity is fundamentally the concentration of hydrogen ions within your soil. It is measured on a pH scale (typically 0–14), which represents the “power of hydrogen”.
The Two Pools of Acidity
Active Hydrogen: Hydrogen ions present in the soil solution (water).
Exchangeable Hydrogen: Hydrogen ions physically attached to clay or humic colloids (negatively charged particles in the soil).
For most crops, the ideal pH is roughly 6.5. Once your pH hits 5.5, acidity starts becoming a major limiting factor for productivity.
Why is Your Soil Acidic?
Acidity can stem from natural sources or management choices:
Parent Material: Soils derived from granite are naturally more prone to acidity than those from basalt.
Nitrogen Fertilizers: This is a primary driver of human-induced acidity. Ammonium-based fertilizers (like MAP, DAP, and Ammonium Sulfate) are highly acidifying because they release hydrogen ions as the plant absorbs them or as they convert into nitrate.
Plant Biology: Legumes and high-yielding crops can acidify the soil as they release hydrogen ions to “trade” for cations like calcium and potassium.
The Problem with Low pH
When soil pH drops below 5.5, several destructive processes occur:
Mineral Lockup: The availability of essential minerals decreases sharply.
Toxicity: Aluminum and Manganese become highly soluble and can reach toxic levels for plants.
Root Stunting: Excessive acidity damages root tips, preventing the development of the massive root systems needed for high yields.
The Regenerative Fix: A Two-Step Approach
We use a combination of chemistry and biology to fix acidic soils.
1. Strategic Liming (The Quick Fix)
If pH is below 5.5, we recommend a small, frequent application of lime or dolomite.
The Goal: Displace hydrogen from the colloid and neutralize it using carbonate.
Precision Math: We use Base Saturation to calculate exactly how much lime is needed to displace the hydrogen without “over-oxidizing” the soil.
- Don’t Under Lime: Applying lime at rates less than 1000kg/ha can often be non-economic.
2. Root Exudates & Microbes (The Long-Term Solution)
Once the pH is above 5.5, we use plants to do the heavy lifting for free.
Alkalizing Exudates: Healthy plants can release bicarbonates and basic materials through their roots, potentially raising the rhizosphere pH by up to two units.
Beneficial Bacteria: Certain microbes, like Bacillus species, release alkaline metabolites that help neutralize soil acidity.
Summary: Maximizing the System
To drive this biological engine, we focus on:
Increased Photosynthesis: Using foliar applications of iron, magnesium, and manganese to push more sugar (and exudates) into the soil.
Continuous Ground Cover: Using cover crops or intercropping to ensure roots are actively managing soil pH year-round.
If you want to start increasing your soil pH to the ideal level and building soil health, then sign up for a free 30-minute consultation with Agresol. We will work through your soil data and give you five actionable recommendations to start your regenerative journey.
