What are the symptoms of magnesium deficiency in plants?
Written by
Liu Xiaohui
Reviewed by
Prof. Martin Thorne, Ph.D.Identifying magnesium-deficient plants quickly prevents permanent crop damage from occurring. Symptoms often begin insidiously, displayed as yellowing on the leaf between the veins while the veins remain green. This symptom is usually first seen at the bottom of the plant, on older leaves. While nitrogen deficiency will usually cause the yellowing to spread across the entire leaf tissue, magnesium deficiency is specific, making the other portions of the leaf [partly] green, specifically between the veins. I've seen hundreds of cases in tomatoes and peppers that were diagnosed and treated with magnesium in weeks (if not months) before the fruit exhibited signs.
Interveinal Chlorosis
- Yellowing between leaf veins while veins remain dark green
- Starts on older mature leaves first before spreading upward
- Distinct from nitrogen deficiency which causes uniform yellowing
- Indicates chlorophyll breakdown due to magnesium shortage
Necrotic Spots
- Brown dead tissue patches at leaf margins and tips
- Develops after prolonged deficiency as cells die
- Spreads inward toward leaf center over time
- Often appears crispy and brittle to the touch
Leaf Curling
- Upward curling along leaf edges creating cup-like shapes
- Plant's attempt to reduce moisture loss from damaged tissues
- More severe in sunny dry conditions
- Different from disease-related curling which shows downward patterns
Symptom advancement demonstrates a predictable pattern consisting of three stages. First, you see a little yellowing on the lower leaves that enlarges over a period of two weeks as chlorophyll production is halted. You then see brown edges as tissues die due to a lack of energy. Finally, leaves curl and fall before the plant dies. I have documented this progression in beans. In this example, the plant completely lost its leaf cover in six weeks without treatment.
Confirm suspected magnesium problems through testing with laboratory analysis. Soil tests report on the available magnesium levels, and it is essential to have plant tissue tests taken from leaves to verify the plant's uptake of magnesium. Ensure that you collect samples from both the healthy plant and the affected plant to facilitate comparison. I also always make sure to have a pH test done, because acid soils with a pH level below 5.5 can accelerate the loss of magnesium. Correct identification avoids wasting an application that may look similar but is not the same.
As soon as you've confirmed the illness, use corrective measures. Epsom salts can be used as a foliar spray to provide quick assistance to affected plants. Adjust the soil pH using dolomitic lime to provide a long-term solution. As new growth begins to develop, look for signs of recovery within a few days. Your swift action prevents permanent loss of the plants and a total loss of crop production!
Read the full article: 7 Critical Signs of Magnesium Deficiency Plants
