MAGNESIUM “I can be your best friend or your worst enemy.”

Written by Mike Hamilton, CCA President of Turf Dietitian, Inc.

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Magnesium’s impact on plants:

Magnesium is a secondary macronutrient essential for plant life, playing a significant role in soil structure and physical condition. Even minor magnesium deficiencies weaken a plant, making it susceptible to many ailments. However, a magnesium deficiency will cause significant stress that will eventually cause plant decline. Toxic effects from excessive Magnesium in the plant are rare but will cause devastating challenges in the soil, playing a decisive role in plant strength.

Unlike nitrogen, phosphorous, and potassium, the plant has smaller demand for Magnesium. This lower demand is why many growers tend to ignore it. Also, magnesium deficiency is hard to diagnose. Many visual symptoms do not appear until the plant is in significant decline, the deficiency usually leading to disease, insects, or other environmental stress factors.

Magnesium plays only a small role in the plant’s primary structural development, but it is the essential nutrient for all secondary metabolic functions. Chlorophyll develops in the early stages of the plant life cycle, and Magnesium is the center of this life-sustaining plant blood. Consequently, if Magnesium is deficient in the plant, the first link in the chain of secondary metabolic function is compromised. Secondary metabolic functions are responsible for producing oxygen and toxins to fight off plant attacks and nourish sugars, acids, and proteins. All of these keep plants healthy and feed the soil bacteria once a plant does expire.

Think about it this way, if a long chain holding up a storage bend has weight added to the bend, that means there will be added stress to the chain. If the top link is weak, the added weight will give way, and the entire bend will come crashing down. The weaker the chain, the faster the bend is going to fall.

Magnesium deficiencies weaken a plant’s ability to accomplish secondary metabolic functions. Such as producing natural protection compounds that prevent and heal them from fungal, viral, and bacterial diseases. Therefore, the disease may be the first visual symptom of a magnesium deficiency. A grower will get caught up in an endless cycle of spraying expensive fungicides when a magnesium deficiency persists.

Magnesium’s impact on soil:

Excessive Magnesium in soil reserve will cause devastating effects on the soil’s structure, creating a lack of flow and buildup of water, forming saturated soils. Magnesium is a small molecule with two positive charges. In layman’s terms, if one positive charge attaches to one soil particle and the other positive charge attaches to a second soil particle, there will be less space for oxygen to move and will form altogether. Excess Magnesium in the soil will also prevent the uptake of other nutrients, further weakening plant health and immunity to life-threatening entities.

What may be difficult to understand is that if the soil has excessive Magnesium, the plant can still be deficient. Even in this rare situation, a constant balancing act with the plant may require constant monitoring to ensure plant and soil health.

Saturated soils commonly contain low levels of soil oxygen. Low oxygen levels reduce beneficial bacteria, root mass, and a plant’s ability to survive any form of stress. Poor root structure hinders the uptake of all nutrients, compromising the plant’s primary and secondary metabolic functions. Simply put, proper amounts of Magnesium are a plant’s best friend, but excessive levels in the soil are a plant’s worst enemy.

Unfortunately, in those situations where excessive levels of Magnesium in the soil exist, it may be exceedingly difficult and costly to remediate the problem.

Review of Magnesium Facts:

• “Magnesium” is a secondary nutrient needed for several functions in the healthy growth of the plant.
• Magnesium gets considered a secondary nutrient, not based on importance but on the amount needed within the plant.
• Magnesium is the center of the chlorophyll molecule, like how iron is the center of the hemoglobin molecule in humans.
• Soils that contain high levels of Magnesium will cause soils to be saturated as Magnesium pulls and holds soil particles tightly together.
• Magnesium deficiencies enhance plant pest attacks.

The Function of Magnesium in the Plant:

 

• Magnesium plays a role in several enzyme reactions. Without Magnesium, plants cannot produce the chlorophyll needed for photosynthesis.
• Magnesium assists in pulling several anions into the plant, such as nitrate, phosphorus, chloride, and sulfur.
• Magnesium plays a significant role in sugar synthesis, oil and fat formation, starch translocation, and iron utilization.

Magnesium Uptake by Plants:

 

• The root system absorbs Magnesium through two methods: diffusion and passive uptake.
• The concentration of Magnesium must be higher in soil solution for diffusion to occur. The transpiration process drives passive uptake (mass flow).
• Foliar fertilizer applications can bypass natural uptake functions with chelators such as sugars, amino acids, and complex carbohydrates to help the leaf tissue absorb Magnesium into the leaf.

Magnesium Deficiency Symptoms:

 

 

• Magnesium deficiency starts with mottled chlorotic areas developing in the interveinal tissue.
• In some cases, it can superficially resemble potassium deficiency.
• Many plant diseases and pest attacks are a symptom of magnesium deficiency.
• Magnesium deficiencies may occur when the following factors affect its availability:
  • Sand: Magnesium deficiencies can occur in sandy soils, low in organic matter.
  • Soil pH: Magnesium availability will decrease in low and high pH soils.
  • Soil Temperature: Low soil temperatures with long periods of cool and cloudy weather.
  • Drainage: Poor drainage causes saturated soil. Which can also be accelerated by high levels of Magnesium.
  • Antagonists: Soils high in levels of calcium, potassium, sodium, and iron can cause magnesium deficiencies.

Magnesium Toxicity:

• Magnesium toxicity in plants is rare.
• Issues associated with excess Magnesium in soils limit the uptake of calcium, phosphorus, potassium, iron, and manganese.

In closing, Magnesium’s impact on overall plant health is cause for careful consideration. Magnesium deficiencies weaken a plant’s ability to accomplish secondary metabolic functions. Neglecting to diagnose magnesium deficiencies can cause long-term and irrefutable damage to plants. Endless cycles of spraying expensive fungicides are avoidable with the right fertility program.

Written by Mike Hamilton, CCA & President of Turf Dietitian.