Maximizing Calcium and Magnesium Bioavailability in Canadian Soils: Actionable Steps for Gardeners

Latest posts by Ashley (see all)

Magnesium and calcium are necessary elements for plant growth, yet Canadian soils rarely lack these nutrients. This is partly because the parent rock and glacial till that make up the majority of Canadian soils have high concentrations of these minerals. The soil pH also has a big impact on how well these minerals are absorbed by the plants.

If you are new to this blog my name is Ashley and I am a soil scientist. I am located in a Canadian Zone 3 and a USDA Zone 4. I write articles, make YouTube videos, Instagram & Facebook posts all designed for Canadians and Cold Climate gardeners using science-based methods. If you are looking for anything specific be sure to let me know in the comments down below.

This is why a poor pH can result in the dreaded blossom end rot we see in tomatoes.

What Is Soil pH

The term “soil pH” describes how acidic or alkaline the soil is. The neutral pH value is 7, and the pH scale goes from 0 to 14. In soils that range in pH from 6 to 7, which are slightly acidic to neutral, plants may access calcium and magnesium more easily. The positively charged ions of calcium and magnesium are more readily absorbed by plant roots under these circumstances.

How does this affect Calcium & Magnesium in our garden soil?

However, calcium and magnesium are less readily available in extremely acidic soils with a pH below 6 because these minerals are less able to neutralize the extra hydrogen ions. On the other hand, because of their low solubility in basic circumstances, these minerals have limited absorption in alkaline soils with a pH over 7.

In order to ensure that the soil pH is within the ideal range for the plants they intend to grow, one of the crucial things for a gardener to do is to get their soil tested to determine the pH.

What does Agriculture and Agri-Food Canada say?

The majority of Canadian soils, according to research by Agriculture and Agri-Food Canada, have a pH range between 5.5 and 7.5, which supports the appropriate availability of calcium and magnesium for plant growth. (Reference: Agriculture and Agri-Food Canada’s 2002 publication, “Soil pH and Soil Test Interpretation for Field Crops“)

One of the reasons Canadian farmers may rely on the natural fertility of their soils and require less lime and fertilizer application, according to another study, “Soil pH and Nutrient Availability,” by the Ontario Ministry of Agriculture, Food and Rural Affairs. (Source: Ontario Ministry of Agriculture, Food and Rural Affairs, “Soil pH and Nutrient Availability,” 2014)

A gardener can take a number of practical actions to raise the magnesium and calcium bioavailability in the soil for plants:

  1. The first thing a gardener should do is test the soil pH and then modify it so that it is in the ideal range for the plants they are cultivating. As indicated before, soils with a pH between 6 and 7 are slightly acidic to neutralize and provide plants with more readily available calcium and magnesium. The gardener can use lime to boost the pH or sulfur to drop the pH if the soil pH is outside of the ideal range.
  2. Gardeners can supplement the soil’s naturally occurring amounts of calcium and magnesium by adding calcium and magnesium fertilizers. Gypsum or lime can be used to add calcium. Keep in mind that this is only a patch for a larger issue at hand.
  3. Use compost: Including calcium and magnesium, using well-rotted compost in the soil can assist to increase its total nutrient content.
  4. Intercropping or crop rotation: Crop rotation, which is planting various plants in the same space at various periods of the year, can help to increase the overall health of the soil and the nutrients’ bioavailability, particularly calcium and magnesium. Intercropping, or growing multiple plants simultaneously in the same space, can also enhance nutrients and soil health.
  5. Application of lime in cases of acidic soil: Lime is a good source of calcium and also aids in bringing the pH of the soil up to a more neutral level, increasing the availability of other nutrients like magnesium to the plants.
  6. Avoid using ammonium-based fertilizers excessively since they can alter the pH of the soil and reduce the bioavailability of calcium and magnesium.

It’s crucial for the gardener to periodically evaluate the pH and nutrient condition of the soil and change the measures as necessary because these actions can take time to produce benefits. Before making any radical decisions, it is advised to have a professional soil analysis performed. The particular steps to be taken will also rely on the plants being cultivated and the soil’s existing condition.
As a result of the high concentrations of these elements in parent rock and glacial till, as well as the soil pH, which promotes their adequate availability for plant growth, calcium and magnesium are rarely lacking in Canadian soils.