Understanding and Managing Magnesium (Mg) Deficiency

Let’s talk about magnesium deficiency. Magnesium is a secondary macronutrient, and while it may not get the same attention as nitrogen, phosphorus, or potassium (NPK), it plays an essential role in various physiological processes. Given its diverse roles in healthy plant development, magnesium deficiency can significantly affect crop productivity and quality.

What is a magnesium deficiency?

Magnesium deficiency is when plants have inadequate magnesium (Mg) levels, an essential macronutrient for their growth and development. This deficiency arises when the soil lacks sufficient magnesium or when factors impede the plant’s ability to absorb magnesium effectively.

Why is magnesium so important for crops?

Magnesium is important for crops because it is a central component of chlorophyll production, enabling photosynthesis and facilitating energy transfer within plants. Moreover, magnesium aids in nutrient uptake, transportation of sugars from source to sink and stress tolerance, influencing crop yield, quality, and overall resilience to environmental challenges. Since magnesium is involved in all sorts of critical plant processes behind the scenes, deficiency can severely impair plant health and productivity.

What are the common signs of magnesium deficiency?

Symptoms of magnesium deficiency typically manifest as interveinal chlorosis, where the areas between leaf veins turn yellow while the veins themselves remain green. Additionally, plants may exhibit stunted growth, leaf curling, and reduced yields.

• Interveinal Chlorosis: One of the most prominent symptoms of magnesium deficiency is interveinal chlorosis, where the tissue between the veins of older leaves turns yellow while the veins remain green. This yellowing occurs because magnesium is a central component of chlorophyll, the green pigment essential for photosynthesis.
• Leaf Curling: In severe cases, leaves may exhibit curling or cupping, along with interveinal chlorosis.
• Stunted Growth: Insufficient magnesium can lead to reduced plant growth in height and overall size.
• Leaf Drop: Affected plants may drop their older leaves prematurely.
• Reduced Fruit Production: Fruit development and quality can be compromised in fruit-bearing plants.

What are the impacts of magnesium deficiency on crop production?

1. Chlorosis & Reduced Photosynthesis: Magnesium is a critical component of chlorophyll, and its deficiency can hinder photosynthesis, which is essential for plant energy production and growth. Since chlorophyll contains magnesium at its core, inadequate magnesium availability can lead to chlorosis by hindering chlorophyll synthesis. As a result, photosynthetic activity decreases, impacting plant growth, development, and overall productivity.
2. Reduced Yield & Quality: Insufficient magnesium affects various physiological processes essential for plant growth, leading to stunted growth, poor development of reproductive structures (such as flowers and fruits), and ultimately reduced crop yield.
3. Impaired Nutrient Uptake: Magnesium deficiency can interfere with the uptake and utilization of other essential nutrients by plants, such as phosphorus, potassium, and nitrogen, leading to secondary nutrient deficiencies.
4. Increased Susceptibility to Stress: Plants deficient in magnesium are more vulnerable to environmental stresses such as drought, heat, and disease. Magnesium plays a crucial role in stress response mechanisms, and its deficiency weakens the plant’s ability to withstand adverse conditions.

How can growers manage magnesium deficiency?

Soil & Tissue/Plant Testing combined use of soil and plant testing as the best way to gauge magnesium levels and uptake by the crop. Because magnesium among cations is the most leachable, plant testing in season is an excellent tool to keep track of the plant magnesium level.

Soil and Plant testing: Combined use of soil and plant testing is the best way to gauge magnesium levels and uptake by the crop. Because magnesium among cations is the most leachable, plant testing in season is an excellent tool to keep track of the plant magnesium level.

Fertilization: Magnesium deficiency can be prevented or remedied through fertilization. Likewise, consistently providing balanced nutrients through an integrated nutrient management plan can ensure plants get what they need when needed. Polysulphate®, a gradual-release granular fertilizer, provides S, K, Ca, and Mg. Foliar-applied fertilizers, like Nova Magnific™ and Nova FLOW™, can easily be absorbed by plants through their leaves and can give crops a quick boost of magnesium when needed.

Organic Matter: Incorporating organic matter into the soil can enhance magnesium availability over time, providing a sustainable solution. Applying manure with OMRI-approved Polysulphate has also been shown to have positive effects on yield.

pH Management: The optimal pH for magnesium absorption by plants typically ranges between 6.0 and 7.0. In this pH range, magnesium is most soluble and readily available for uptake by plant roots. However, variations are common. Soil pH can be adjusted to influence magnesium availability. In acidic soils, magnesium may be less accessible to plants, so raising the pH to a more neutral level can aid in nutrient uptake. Choosing fertilizers that promote uptake in low-pH soils can also be effective tools. Agrolution High K CalMag 11-6-20 +6Ca +1.5Mg is a non-acidic water-soluble fertilizer that is designed for low pH soils and low alkaline water,

Proper Irrigation: Ensure irrigation practices don’t exacerbate nutrient leaching. Well-timed and measured irrigation helps maintain nutrient availability, including magnesium, for plant uptake. Additional tools, like H2Flo soil surfactant, can also help to improve irrigation practices.

How does magnesium deficiency affect specific crops?

Certain crops, such as potatoes, tomatoes, and citrus fruits, have higher magnesium requirements and are more prone to deficiency if fertilization does not provide adequate magnesium, however, proper fertilization and soil management is essential for maintaining optimal health, yield, and quality across all crops.

• Potatoes: Magnesium deficiency in potatoes leads to reduced tuber size and quality, along with symptoms like yellowing between leaf veins and stunted growth, ultimately resulting in decreased yields.
• Tomatoes: Tomato plants with magnesium deficiency display yellowing of older leaves, reduced fruit set and size, uneven ripening, and poor flavor development, ultimately impacting overall yield and quality.
• Citrus: Citrus trees suffering from magnesium deficiency show yellowing of older leaves, decreased fruit yield and quality, including smaller fruit size, uneven development, and reduced juice content, increasing susceptibility to diseases and pests.
• Soybeans: In soybeans, magnesium deficiency causes chlorosis of older leaves, followed by necrosis if untreated, impairing photosynthesis and nitrogen fixation, leading to decreased yields.
• Corn: Magnesium deficiency in corn results in interveinal chlorosis on lower leaves, progressing to upper leaves, impacting kernel development, stalk strength, and overall yield.
• Almonds: Almond trees suffering from magnesium deficiency show symptoms like yellowing between leaf veins and leaf curling, leading to poor nut development, reduced yields, and compromised nut quality.

The bottom line is that magnesium deficiency can occur across any region and crop in the US. Although it might be more common in the acidic soils of the Southern US and sandy soils in Florida and the Midwest, any area with intensive cropping, substantial rainfall, or crops requiring high magnesium levels faces the risk of deficiency. To effectively prevent and manage deficiencies, we suggest soil testing, in season tissue testing, targeted fertilization, and a balanced and integrated approach to nutrient management.