How To Control Manganese Deficiency in Plants

Manganese plays a critical role in plant health, serving as a cofactor for enzymes and facilitating vital processes like photosynthesis and nitrogen assimilation. However, when plants experience manganese deficiency, their growth, productivity, and overall health can suffer. The consequences include stunted growth, chlorosis, and decreased crop yields, significantly impacting agricultural output.

In this article, we’ll explore how to identify manganese deficiency in plants, the causes behind it, and the best strategies to control and prevent it. By following these guidelines, you can ensure that your plants thrive and maintain their optimal health.

What is Manganese Deficiency in Plants?

Manganese (Mn) deficiency is a widespread problem, most often occurring in sandy soils, organic soils with a pH above 6 and heavily weathered, tropical soils. In contrast, highly-acidic soils increase the availability of this nutrient. Excessive or unbalanced use of fertilizers may also result in some micronutrients competing with each other to become available to the plant. Mn has an important role in photosynthesis and nitrate assimilation. Like iron, boron and calcium, manganese is immobile within the plant, accumulating mostly in the lower leaves. This explains why the symptoms develop first on young leaves. Manganese is an essential micronutrient that supports various biochemical processes in plants. It is involved in:

• Chlorophyll Synthesis: Vital for photosynthesis, manganese helps plants capture light energy efficiently.
• Enzyme Activation: Serves as a cofactor for enzymes involved in respiration and nitrogen metabolism.
• Lignin Formation: Strengthens cell walls, aiding in disease resistance and structural integrity.

When plants lack sufficient manganese, these processes are disrupted, leading to physiological and visual symptoms that can hinder plant development.

Symptoms of Manganese Deficiency in Plants

Visual Symptoms

Manganese deficiency primarily manifests as a variety of visual symptoms on plant foliage, which are crucial for early diagnosis.

• Interveinal Chlorosis: One of the most distinctive signs, interveinal chlorosis appears as yellowing between the veins of younger leaves. This is due to impaired chlorophyll production. The veins remain green while the surrounding tissue turns yellow, creating a stark contrast.
• Necrotic Spots: Brown necrotic spots or streaks may develop on affected leaves, particularly in advanced stages of deficiency. These spots often result from cell death caused by metabolic disruptions.
• Curling or Deformation: In some plants, manganese deficiency can cause leaf margins to curl or distort, reducing the overall leaf area available for photosynthesis.

• Species-Specific Symptoms:
  • Cabbage: Mottled yellowing of leaves, which can sometimes lead to the eventual collapse of the foliage.
  • Beetroot: Leaves exhibit a triangular shape with curled edges and a characteristic speckled appearance referred to as “speckled yellows.”
  • Onions and Sweetcorn: Prominent yellow stripes along the length of the leaves, often starting at the base and extending upward.
  • Tomatoes: A net-like pattern forms as the veins remain green while interveinal regions yellow, accompanied by reduced leaf size and vigor.

Growth Symptoms

In addition to visible leaf changes, manganese deficiency can significantly affect the overall growth and development of plants:

1. Stunted Growth: Plants experiencing manganese deficiency often exhibit slower growth rates due to disrupted metabolic and enzymatic activities.
2. Delayed Maturity: The deficiency can delay flowering and fruiting processes, impacting the harvest timeline and reducing crop yield.
3. Reduced Disease Resistance: Manganese is essential for the formation of lignin, a component of cell walls that provides structural support and resistance to pathogens. Deficiency can make plants more vulnerable to infections.
4. Loss of Vigor: Affected plants may appear lackluster, with dull and drooping foliage.

Causes of Manganese Deficiency in Plants

Manganese deficiency is typically caused by a combination of soil and environmental factors that limit the availability or uptake of manganese. Understanding these causes is crucial for effective management and prevention.

Soil Factors

1. High Soil pH (Alkaline Conditions): Alkaline soils, with pH levels above 6.5, significantly reduce the solubility of manganese, making it unavailable for plant absorption. In such soils, manganese ions form insoluble compounds, rendering them inaccessible to plant roots.
2. Well-Drained Neutral or Calcareous Soils: These soils often have low levels of available manganese due to natural deficiencies. Their mineral composition and drainage properties exacerbate the issue by leaching away soluble manganese.
3. Low Organic Matter Content: Soils lacking organic matter often struggle to retain micronutrients, including manganese. Organic matter helps bind manganese in a bioavailable form and supports microbial activity that aids in nutrient cycling.
4. Excessive Fertilizer Use: Over-application of lime or phosphate fertilizers can interfere with manganese uptake. Lime increases soil pH, while high phosphate levels can create nutrient imbalances by competing with manganese for uptake pathways.

Environmental Factors

1. High Bicarbonate Levels in Irrigation Water: Irrigation water with high bicarbonate concentrations can exacerbate manganese deficiency, particularly in alkaline soils. Bicarbonates increase soil pH and further reduce manganese availability.
2. Poor Soil Drainage and Waterlogging: Waterlogged conditions can cause a temporary reduction in manganese availability by altering soil chemistry. Reduced oxygen levels in saturated soils can lead to the formation of insoluble manganese compounds, restricting plant uptake.
3. Soil Compaction: Compacted soils limit root penetration and reduce aeration, hindering the plant’s ability to access manganese. Restricted root systems also affect the overall efficiency of nutrient absorption.
4. Seasonal Variations and Weather: Prolonged dry periods or drought conditions can exacerbate manganese deficiency, as nutrient availability and root absorption decrease in dry soils. Conversely, excessive rainfall can leach manganese from the soil, especially in sandy soils with poor retention capacity.

Crop and Plant-Specific Factors

1. Crop Sensitivity: Certain crops, like beans, onions, and cereals, are more sensitive to manganese deficiency than others. Understanding the specific nutrient requirements of your crops is essential for effective management.
2. Varietal Differences: Even within a crop species, different varieties may have varying tolerance levels to manganese deficiency. Selecting tolerant varieties for known problem areas can mitigate symptoms.
3. Root Health and Function: Diseased or damaged root systems are less effective at absorbing manganese, even if it is present in the soil. Root health is often compromised by nematodes, fungal infections.

Human-Induced Causes

1. Over-Cultivation: Continuous tilling or soil disturbance can disrupt soil structure and microbial activity, leading to manganese deficiencies over time.
2. Irrigation Practices: Excessive or poorly managed irrigation can contribute to waterlogging or leaching, both of which reduce manganese availability.

How To Control Manganese Deficiency in Plants

Controlling manganese deficiency in plants requires a strategic approach that addresses the root cause of the deficiency while ensuring plants receive adequate manganese for optimal health and growth. Here are some effective strategies:

1. Adjust Soil pH

• Acidify Alkaline Soils:
  • Apply elemental sulfur to gradually lower soil pH over time. Sulfur is converted to sulfuric acid by soil bacteria, helping to acidify the soil naturally.
  • For faster results, use ammonium sulfate, a fertilizer that simultaneously supplies nitrogen and acidifies the soil.
• Avoid Over-Liming: Monitor lime applications carefully to prevent excessive pH increases. Test soil regularly to maintain an optimal pH range for manganese availability (5.5–6.5).

2. Apply Manganese Fertilizers

• Soil Application: Use manganese sulfate or manganese oxide, applying it evenly to the soil surface or through band placement near the root zone. Typical application rates are 50–100 kg/ha, depending on crop needs and soil conditions.
• Foliar Sprays: Foliar application provides a quick remedy for visible deficiency symptoms. Prepare a 0.5–0.8% manganese sulfate solution (5–8 g/L) and apply it to foliage during the early morning or late evening to minimize evaporation.
• Chelated Manganese: Use chelated manganese (Mn-EDTA or Mn-DTPA) in soils with high pH to ensure better nutrient absorption by plants.

3. Improve Soil Drainage & Irrigation Practices

• Raised Beds: Create raised beds or mounds to improve water drainage in areas prone to waterlogging.
• Organic Matter Addition: Incorporate compost or well-rotted manure to enhance soil structure, improve drainage, and increase manganese retention.
• Avoid overwatering or using irrigation water high in bicarbonates. Use rainwater or treated water with lower alkalinity where possible.

5. Balanced Fertilization

• Avoid excessive phosphorus and iron fertilization as these nutrients can interfere with manganese availability.
• Use integrated nutrient management to balance macro and micronutrient levels.

Preventive Measures of Manganese Deficiency in Plants

• Check the pH of the soil and adjust if necessary to get the optimal range for the best absorption of the nutrients.
• Plan a good drainage of fields and do not over-water the crop.
• Use organic mulch to keep soil moisture stable.
• Always keep in mind that only balanced fertilization can lead to optimal plant health and increased yield.
• Choose plant varieties less susceptible to manganese deficiency.
• Use water with appropriate bicarbonate levels to prevent exacerbating the deficiency.

How Long Does It Take for a Plant to Recover from a Manganese Deficiency?

The recovery time for a plant affected by manganese deficiency depends on several factors, including the severity of the deficiency, the method of correction, the plant species, and environmental conditions. Here’s a breakdown of what to expect:

1. Mild Deficiency

• Recovery Time: 1–2 weeks.
• Plants with mild symptoms, such as slight interveinal chlorosis, often recover quickly once manganese is supplied. Foliar sprays can yield visible improvements within days as the manganese is directly absorbed by the leaves.

2. Moderate Deficiency

• Recovery Time: 2–4 weeks.
• If the deficiency has caused noticeable yellowing or reduced plant vigor, it may take longer for plants to regain full health. Soil applications of manganese fertilizers can be slower to show results, as they rely on root uptake and soil chemistry adjustments.

3. Severe Deficiency

• Recovery Time: 4–6 weeks or more.
• For plants with advanced symptoms, such as necrotic spots, stunted growth, or deformed leaves, recovery is more gradual. Damaged tissues cannot regenerate, so the plant must produce new, healthy growth once the deficiency is corrected.

You may also like:

• Boron deficiency in plants: Symptoms & Treatments
• How to Identify and Fix Iron Deficiency in Plants
• How to Fix Magnesium Deficiency in Plants: An Urgent Problem
• Phosphorus Deficiency Causes, Symptoms & Treatments
• Nitrogen Deficiency Symptoms and Treatment
• How to Fix Calcium Deficiency in Plants: 2024 Guide

Frequently Asked Questions

Conclusion

Manganese deficiency in plants, though a common challenge, is highly manageable with proper diagnosis and timely intervention. From recognizing the early signs of interveinal chlorosis to implementing corrective measures such as foliar sprays, soil amendments, or pH adjustments, there are numerous ways to restore balance and ensure optimal plant health.

By understanding the critical role manganese plays in plant physiology and taking proactive steps to address deficiencies, you can protect your plants from stunted growth, reduced yields, and diminished vitality. Remember, a well-balanced nutrient profile and regular soil testing are the foundation of successful plant care.

Empower your plants with the care they need, and they’ll reward you with robust growth and a bountiful harvest.