What Is Fertilizer Burn and How Does It Affect Plants?
Fertilizer burn refers to damage caused to plants when fertilizers are applied in excessive amounts or improperly. Fertilizers contain salts and nutrients that, in high concentrations, create a harmful environment around plant roots or on foliage. This can lead to dehydration, nutrient imbalances, and cellular damage, ultimately harming or killing the plant.
The primary mechanism behind fertilizer burn is osmotic stress. When too much fertilizer is present, the soil solution becomes highly concentrated with soluble salts. This causes water to move out of the plant roots into the soil to balance the salt concentration, leading to dehydration of plant cells. In addition, excessive salts can interfere with nutrient uptake, compounding the stress.
Common Causes of Fertilizer Burns in Plants
1. Over-Application of Fertilizers
The most frequent cause is applying more fertilizer than the plant can safely absorb. This might happen if you follow incorrect dosage instructions or apply fertilizer too often. Over-fertilizing both granular and liquid fertilizers can cause burns.
2. Using High Concentration Liquid Fertilizers Directly on Foliage
Foliar feeding with undiluted or overly concentrated fertilizers can cause leaf scorch and burn. Always dilute liquid fertilizers as per label directions if applying to leaves.
3. Applying Fertilizer on Dry Soil
Spreading fertilizer on dry soil without subsequent watering increases salt concentration near roots, raising burn risk. Moist soil helps dilute salts and reduces osmotic stress.
4. Using Fertilizers with High Salt Index
Some fertilizers, such as ammonium nitrate and potassium chloride, have a higher salt index and are more likely to cause burns if misapplied.
5. Improper Timing and Weather Conditions
Applying fertilizers during hot, dry weather or when plants are stressed (drought, transplant shock) can increase vulnerability to fertilizer damage.
Symptoms and Signs of Fertilizer Damage on Plants
Recognizing fertilizer burn early can save your plants. Watch for these symptoms:
- Leaf Discoloration: Yellowing or browning of leaf edges and tips is common.
- Leaf Curling and Wilting: Leaves may curl, dry out, or wilt despite adequate watering.
- Scorched or Burned Spots: Visible necrotic patches, usually starting on older leaves.
- Stunted Growth: New growth may be reduced or deformed.
- Root Damage: Roots may appear darkened, mushy, or shriveled upon inspection.
It’s important to differentiate fertilizer burn from other issues like pests or diseases, but the pattern of damage near fertilizer application points is a strong indicator.
Types of Fertilizers Most Likely to Cause Burns
1. Synthetic Chemical Fertilizers
These often contain high concentrations of nitrogen, phosphorus, and potassium salts. Examples include urea, ammonium nitrate, and potassium chloride. Their high solubility can lead to salt buildup quickly if overused.
2. Granular Fertilizers
If applied too heavily close to plant stems or roots, granules dissolve and create localized salt concentrations causing root burn.
3. Liquid Fertilizers
Undiluted or strongly concentrated liquid fertilizers, especially when sprayed on foliage, can cause leaf scorch.
4. Manure and Compost Tea
While generally safer, poorly composted manure or overly concentrated compost teas can have high ammonia or salt content, potentially burning plants.
How to Prevent Fertilizer Burn: Best Practices for Application
- Follow Label Instructions: Always apply fertilizers at recommended rates and dilutions.
- Test Soil Nutrient Levels: Conduct soil tests periodically to apply the right amount of nutrients and avoid over-fertilizing.
- Water Before and After Application: Moist soil reduces salt concentrations and helps nutrients absorb properly.
- Apply Fertilizer Evenly: Avoid piling fertilizer near stems or root crowns.
- Use Slow-Release or Organic Fertilizers: These reduce the risk of quick salt buildup.
- Time Applications Appropriately: Avoid fertilizing during extreme heat or drought stress.
- Dilute Liquid Fertilizers: Never apply liquid fertilizers at full strength unless specified.
FAQs About Fertilizer Burns
Q1: How long does it take for fertilizer burn to show up?
Symptoms can appear within a few days to a week after application, depending on fertilizer type and concentration.
Q2: Can fertilizer burn kill plants?
Yes, severe fertilizer burn can kill plants, especially seedlings or sensitive species.
Q3: What should I do if I suspect fertilizer burn?
Immediately flush the soil with plenty of water to dilute salts. Remove damaged leaves and avoid further fertilizing until the plant recovers.
Q4: Are organic fertilizers safer than synthetic fertilizers?
Generally, organic fertilizers release nutrients more slowly and have lower salt content, reducing burn risk. However, improper use can still cause damage.
Q5: Can fertilizer burn affect vegetable crops?
Yes, vegetables are often sensitive to fertilizer burn, especially when young or grown in containers.
Key Takeaways for Home Gardeners and Small-Scale Farmers
- Fertilizer burn is caused by excessive salts from over-application or improper fertilization practices.
- Symptoms include leaf browning, curling, stunted growth, and root damage.
- Synthetic chemical fertilizers and concentrated liquids pose the highest risk.
- Prevent burns by following label directions, watering adequately, and applying fertilizers judiciously.
- Early detection and prompt flushing can help save affected plants.
References
- University of Maryland Extension – Fertilizer Burn in Plants
- Agriculture.com – Fertilizer Burn: Why It Happens and How to Avoid It
- Gardening Know How – Fertilizer Burn in Plants
- USDA Natural Resources Conservation Service – Fertilizer Management Guide
E. Tasnim