FAQ: Understanding and Managing Low pH Soils in Western Canada

Date: February 17, 2025

1. What is low pH soil, and how is it defined?

Low pH soil is soil with a pH below 6.6, where the level of acidity begins to affect soil function.

Neutral soil: pH 6.6–7.3
Moderately acidic soil: pH 5.6–6.5
Strongly acidic soil: pH below 5.5
Low pH soils are common in Western Canada and can significantly impact soil productivity. The pH measures hydrogen ion (H⁺) concentration, with higher levels of H⁺ indicating greater acidity.

2. What causes low pH in soils?

Low pH can result from several natural and human-influenced processes:

Rainfall and leaching: Natural rainfall, which is slightly acidic, can leach basic nutrients, leaving H⁺ ions behind.
Acid rain: Industrial emissions can lead to sulfuric and nitric acid deposition.
Microbial processes: Nitrification of ammonium releases H⁺ ions.
Fertilizer use: Nitrogen fertilizers like ammonium nitrate, ammonium sulfate, and MAP contribute to soil acidification.
Soil mineral content: Weathering of minerals like feldspar and mica can release aluminum, which further lowers pH.

3. Why is low soil pH a problem?

Low pH affects crop growth through three main mechanisms:

Nutrient availability: At low pH, essential nutrients (e.g., phosphorus, potassium, magnesium) become insoluble and unavailable to plants, while toxic metals like aluminum and manganese become more soluble.
Toxicity: Soluble aluminum damages plant root cells, reduces calcium uptake, and forms insoluble aluminum-phosphorus compounds, further depriving plants of nutrients.
Microbial activity: Acidic conditions reduce bacterial activity essential for nutrient cycling, while fungi are less affected but may not fully compensate for lost bacterial functions.

4. What are the structural impacts of low pH on soil?

Low pH disrupts soil aggregation, which is critical for structure and resistance to compaction:

Microaggregate stability: Microaggregates are small clusters of soil particles bound together by organic matter, minerals, and microbial secretions. They are essential for maintaining soil structure, as they improve water retention, aeration, and resistance to erosion. Acidic conditions destabilize soil colloids, preventing the formation of these crucial microaggregates, which can lead to poor soil health and reduced plant growth.
Macroaggregate formation: Aluminum toxicity weakens roots and reduces exudates, which are vital for creating and maintaining larger soil aggregates.
Compaction: Poor soil structure and weak aggregation leave soils vulnerable to compaction and erosion.

5. How can low pH soils be managed?

Low pH disrupts soil aggregation, which is critical for structure and resistance to compaction:

Microaggregate stability: Microaggregates are small clusters of soil particles bound together by organic matter, minerals, and microbial secretions. They are essential for maintaining soil structure, as they improve water retention, aeration, and resistance to erosion. Acidic conditions destabilize soil colloids, preventing the formation of these crucial microaggregates, which can lead to poor soil health and reduced plant growth.
Macroaggregate formation: Aluminum toxicity weakens roots and reduces exudates, which are vital for creating and maintaining larger soil aggregates.
Compaction: Poor soil structure and weak aggregation leave soils vulnerable to compaction and erosion.

6. How does low pH affect microbial communities?

Soil pH is a critical determinant of microbial composition:

Bacteria: Sensitive to small pH changes and often less effective in acidic soils.
Fungi: More resilient to low pH and capable of substituting bacterial functions in nutrient cycling, disease resistance, and organic matter decomposition.
H-Start’s role: Its diverse fungal strains ensure functional redundancy, maintaining soil health even under challenging conditions.

7. What is H-Start, and how does it help in acidic soils?

H-Start is a mature, compost-based, pelleted soil amendment. It contains naturally occurring soil fungi and bacteria in a live, dormant state. It is adapted to thrive in low pH soils. Key benefits include:

Aluminum detoxification: Fungi in H-Start can bind to and immobilize toxic aluminum, reducing its harmful effects on plants.
Nutrient solubilization: H-Start fungi unlock phosphorus, potassium, and magnesium from acidic soils.
Disease suppression: The fungal community competes with pathogens, reducing disease pressure.
Soil structure improvement: Fungal hyphae support soil aggregation by stabilizing microaggregates and enhancing nutrient cycling.

8. Can H-Start improve soil structure under acidic conditions?

Yes, H-Start can mitigate the structural degradation caused by low pH through:

Binding of toxic ions: Reduces the negative effects of aluminum on soil aggregation.
Root-fungi associations: Enhances root secretions and nutrient uptake, promoting aggregation.
Fungal hyphal networks: Stabilize soil particles and improve water infiltration and retention.

Learn More About H-Start

If you’re dealing with low pH soils on your farm, H-Start can provide a sustainable path to more productive crops and healthier soil.