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Grapes Magnesium Deficiency | Causes & How to Control

Grape Magnesium deficiency has been more common on sandy, acidic soils. Magnesium deficient vines have older leaves that are pale in color. This article will help you understand Mg deficiency on the grape. (Most Common Grapevine Diseases)

grapes magnesium deficiency

The common fruits such as grapes have a great demand for Magnesium, Magnesium’s effect is essential for grape, it can be called “a large number of elements” for grapes, and the demand is similar to phosphorus.

Even the magnesium content of grape leaves is higher than that of phosphorus. It is directly involved in physiological and biochemical processes such as photosynthesis and enzyme activation of grapes. It is one of the mineral elements necessary for normal growth and development of grapes and improvement of fruit quality.

Chlorophyll synthesis and photosynthesis

Magnesium accounts for 2.7% of the molecular weight of chlorophyll. It is the central atom of chlorophyll a and chlorophyll b porphyrin ring in chloroplasts and plays an essential role in the synthesis and photosynthesis of chlorophyll.

In the absence of magnesium, the chloroplast structure of the grape was destroyed, the number of basal particles decreased, the number of thylakoids decreased, photosynthesis was affected, and the leaves were chlorotic yellow.

Plant physiological metabolism

Plants are continually undergoing various physiological, metabolic activities. Almost all metabolic processes require magnesium ions to regulate and activate enzymatic reactions, such as photosynthesis, sulfate reduction, respiration, glycolysis. They all rely on magnesium to enable.

Also, the lack of magnesium in the crop causes protein synthesis to be blocked. At the same time, it will intensify the induction of membrane lipid peroxidation and accelerate the senescence of plant leaves.

Participate in grape growth

Grape plants need more magnesium. The photosynthesis of grapes, the conversion of phosphorus, the formation of pectin substances and vitamin A, and the elimination of the harmful effects of excess calcium are all inseparable from the participation of magnesium.

The right amount of magnesium can promote grape shoots and leaves. Root growth, stable organ structure.

Improve the yield and quality of grapes

Magnesium can promote photosynthesis, strengthen carbon dioxide fixation and dry matter accumulation, which is an important factor affecting the formation of grape quality.

The lack of magnesium in grape plants directly leads to the grapefruit being smaller, the sugar content is low, the berry color is poor, the maturity period is delayed, and the yield is reduced.

Symptoms of Grape Magnesium Deficiency

Because magnesium can be transferred to young parts in plants, the top leaves are asymptomatic.

Initially starting from the base blade, the leaf edge turns yellow first, the leaves are water-stained, and the yellow veins are severe.

The magnesium-deficient grape is prone to leaf shrinkage, the middle leaves are shed, and the branches are bare. Symptoms of magnesium deficiency such as chlorosis and necrosis on the leaves are more likely to occur when the light intensity is high.

Magnesium deficiency can also cause the branches to be slender and weak, the roots are less, the flowering is inhibited, and the flowers are pale.

In the absence of magnesium, the fruit swells slowly, the coloration is poor, and the maturity period is delayed. In severe cases, the stalk is atrophied.

Causes of Grapes Magnesium Deficiency

1. The soil is mostly acidic, the pH value is too low, the magnesium leaching is serious, the release of magnesium is obviously inhibited, and the average content of exchangeable magnesium in the soil is lower than the critical level, and the magnesium deficiency is serious.

2. Grapes are potassium-producing crops, but excessive potassium inhibits the absorption of magnesium by the roots of the grapes and transports magnesium ions to the above-ground parts, causing magnesium deficiency.

3. Magnesium and calcium, ammonium ions also have antagonistic effects, therefore, the soil calcium content is too high or the application of calcium and nitrogen fertilizers will reduce the absorption of magnesium by plants.

4. Years of high yields took away a lot of magnesium but did not replenish in time, resulting in magnesium deficiency.

How to Solve Grape Magnesium Deficiency

Pre-growth period: At this time, it is in the critical period of magnesium nutrition, which is generally applied in the form of base fertilizer, and the effect is obvious.

Grape fruiting period: Grape magnesium deficiency occurs mainly in the late growth stage. At this time, a large amount of potassium fertilizer application will inevitably exacerbate the symptoms of magnesium deficiency. In addition to magnesium, the lack of magnesium affects the current year’s output, causing premature senescence of the yellow leaves and early leaves. It will also cause the grapes to spend fewer flowers in the coming year, so we must pay attention to supplement.


1 Phosphorus in soil has a strong immobilization effect on magnesium and is difficult to be absorbed by roots. It is recommended to choose chelated magnesium.

2 For acidic soils, it should be timely adjusted to avoid magnesium deficiency caused by magnesium leaching.

3 Magnesium fertilizer must be combined with other fertilizers to be effective.

4 Foliar spray magnesium, the effect is significant, but not lasting, should be sprayed several times.

5 Excessive application of magnesium fertilizer not only leads to the imbalance of nutrient elements, but also affects the absorption of other elements by plants.

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