What natural sources provide magnesium for plants?
Written by
Liu Xiaohui
Reviewed by
Prof. Martin Thorne, Ph.D.Natural sources of magnesium can sustainably nourish crops with magnesium deficiencies, eliminating the need for chemical interventions. Organic mineral sources slowly release magnesium nutrients to meet the crop's needs and enhance the soil's structure. I have kept a garden thriving that required magnesium and was depleted of it, using only compost and rock minerals. Natural sources of magnesium are well-suited for use in organic systems and sensitive ecosystems.
Composted Manure
- Contains 0.1-0.6% magnesium depending on animal diet
- Releases nutrients slowly over 2-3 growing seasons
- Improves soil structure and water retention
- Apply 1-2 inches annually as top dressing or till in
Dolomitic Limestone
- Provides 10-12% magnesium carbonate content
- Raises soil pH while supplying magnesium
- Takes 3-6 months to fully break down
- Apply 5-10 lb/100 sq ft based on soil test results
Greensand & Seaweed
- Glauconite sand contains 3-7% magnesium
- Seaweed extracts offer trace minerals
- Stimulates beneficial microbial activity
- Use 5-10 lb greensand or 1 gal seaweed extract/100 sq ft
When applying to maximize impact, consider the timing of your application. Compost manure in the fall for winter breakdown. Incorporate dolomitic lime before spring planting for best results. Greensand will be aided by seasonal rain dissolving minerals. I aim to utilize natural precipitation patterns for timing applications to reduce watering.
Use caution when using ash due to its impact on pH levels. Hardwood ashes contain 1-5 magnesium, but they increase the pH dramatically. Apply only 5-10 lbs of ash per 1000 square feet per year on acidic soils. I only reserve ash for blueberries as they need a reduction in acidity and magnesium. Always wear gloves when handling ash tree ash to protect your skin.
To create a well-rounded fertility program, define a compost system with composted manure and greensand for both immediate and long-term feeding. Dolomite applications on a 3-year rotation will minimize the risk of pH creep. Observe the color enhancement and vigor of the plants as indicators of a successful nutritional regimen. With this sustainable model, you are also building healthy soil for future seasons.
Read the full article: 7 Critical Signs of Magnesium Deficiency Plants
