What are the symptoms of magnesium deficiency in grapes? How to prevent it?

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Grape magnesium deficiency** and how to prevent it.

2015-01-11 Seed net.

What are the dangers of magnesium deficiency in grapes? What causes magnesium deficiency in grapes? How to prevent magnesium deficiency in grapes? Please also ask netizens with experience in grape planting to help introduce.

Grapes are perennial vines, which are generally cultivated in greenhouses or equipment trellises, resulting in the inability of the vineyard soil to be ploughed for a long time, so that the elements in the soil are deposited or lost, resulting in the formation of nutrient deficiency symptoms. Today, the farming network has sorted out the hazards, causes and prevention methods of grape magnesium deficiency, and the following is listed in detail for the reference of netizens.

1. The harm of grape magnesium deficiency:

When the grape is deficient in magnesium, the old leaves at the base of the vine obviously lose green and are yellowish-white to grayish-white, with clear reticulate veins and purple veins. The veins of the middle leaves of the grape are green, and the veins are yellowish-green. The upper leaves of the grape are water-stained, and later form large necrotic patches; Magnesium-deficient grapes had poor coloration, delayed ripening, and low sugar content, but there was little variation in grain size and yield.

2. Causes of magnesium deficiency in grapes:

The cause of grape magnesium deficiency is mainly caused by insufficient amount of organic fertilizer application or poor quality of organic fertilizer, resulting in insufficient replaceable magnesium in the soil. Because magnesium is easily lost in acidic soils, large amounts of potassium, lime or sodium nitrate can affect the absorption of magnesium in grapes, which can easily cause magnesium deficiency. In addition, after the heavy rains in the summer, the magnesium deficiency of the grapes can occur significantly.

3. Prevention and control methods of grape magnesium deficiency:

Method 2: When the grapes begin to have magnesium deficiency, the grape foliar spray with a magnesium sulfate solution with a content of 3% 4% can be sprayed once every 20 30 days, and it needs to be sprayed 3 or 4 times. Click to view.

Method 3: In the vineyard with serious magnesium deficiency, 100 kg of magnesium sulfate can be applied per mu, and magnesium sulfate can be applied by ditching, and kilograms of mature grapes can be applied for two years. The mixed application of magnesium sulfate and organic fertilizer has a better effect.

Magnesium deficiency in grapes causes these symptoms: yellowing of leaves, reduced photosynthesis capacity, and impaired transport of sugars to flowers and fruits. In more severe cases, it will cause uneven color change, a decrease in firmness and the size of the grapes, and the tree will be more susceptible to disease after the decline in the hardness of the grape grains.

The reason for these symptoms is that the grapes are most likely to have magnesium deficiency during the growing period, when the grapes are most likely to suffer from magnesium deficiency during the period when the grapes are enlarged and veraison, which accounts for 56% of the grapes' vegetative period.

You can use magnesium-rich water-soluble fertilizers, such as Dafeng Harvest Shidezan water-soluble fertilizer, which can automatically replenish the nutrients required by the tree according to the nutrient needs of grapes at different stages. Recommended.

Magnesium is an important component of chlorophyll, a component of the intercellular layer of the cell wall, and a component and activator of a variety of enzymes, which has a certain impact on respiration and sugar conversion, can promote the absorption and transportation of phosphorus, and can eliminate excess toxicity. Among fruit trees, grapes are most susceptible to magnesium deficiency. It is mainly due to the lack of replacement magnesium in the soil, the root cause of which is the poor quality and quantity of organic fertilizer, and the fertilizer source mainly relies on chemical fertilizers, resulting in insufficient magnesium in the soil.

Magnesium deficiency is more common in vineyards in southern China because magnesium is more likely to be lost in acidic soils. Excessive application of potassium fertilizer, or high application of sodium nitrate and lime in orchards, can also affect magnesium absorption, and magnesium deficiency often occurs. It is even more pronounced after heavy rains in summer.

Magnesium deficiency in fruit trees is mainly caused by the lack of giving magnesium in the soil, generally speaking, there is no lack of magnesium in the soil, and when there is too much magnesium, it has a toxic effect and affects the growth of fruit trees. For example, excessive magnesium poisoning sometimes occurs in alkaline soils, and magnesium deficiency often occurs in orchards with acidic soils, or continuous potassium fertilizers, or large amounts of sodium nitrate and lime.

Magnesium supplementation is to supplement magnesium elements, Miao Shengcai micro fertilizer contains a variety of trace elements, can promote the balanced absorption of grape nutrients, improve the yield to choose Miao Shengcai.

Magnesium sulfate can be administered to correct it.

Symptoms of grape magnesium deficiency: mainly from the old leaves at the base of the plant, initially the old leaves between the veins of the green fade, and then between the veins of the leaf develop into banded yellowing spots, mostly from the leaf ** to the leaf margin, gradually yellowing, and finally the mesophyll tissue yellow-brown necrosis, only the leaf veins remain green.

As a result, the yellow-brown necrotic mesophyll is well demarcated from the green veins. The symptoms are not obvious in the early stage of growth, and gradually aggravate after entering the fruit expansion stage, and a large number of yellow leaves appear before the fruit is ripe in the plant with more fruit set, and the diseased leaves generally do not fall early. Magnesium deficiency had no obvious effect on fruit size and yield, but fruit coloration was poor, ripening was delayed, and quality was reduced.

Symptom characteristics, mostly in the fruit expansion stage, gradually aggravated. First of all, the old leaves at the base of the plant fade green between the veins, and then develop into band-like yellowing spots between the veins, which mostly develop from the inside of the leaves to the leaf margins, and gradually yellow, and finally the mesophyll tissue becomes brown and necrotic, leaving only the leaf veins to remain green, and the necrotic brown mesophyll and the green leaf veins are clearly defined, and the diseased leaves generally do not fall off. The fruit ripening period of magnesium-deficient plants is generally delayed, the berry coloration is poor, the sugar content is low, and the fruit quality is significantly reduced.

The pathogenesis is that the basal old leaves first show the symptoms of greening, and then gradually expand to the upper young leaves. Generally, the symptoms are not obvious in the early stage of growth, and the symptoms begin to show symptoms from the fruit expansion period and gradually worsen, especially for plants with too much fruit set, a large number of yellow leaves appear before the fruit is ripe, and the yellow leaves generally do not fall early. In addition, magnesium deficiency is most common in vineyards in the south due to the high risk of magnesium loss in acidic soils and sandy soils in rainy areas.

Another reason is that excessive potassium application can also affect magnesium absorption, resulting in magnesium deficiency.

Control measures, apply more high-quality organic fertilizer, enhance tree potential. Do not apply too much potassium fertilizer, and maintain high levels of potassium and magnesium to meet the nutritional needs of crops. Balanced fertilization of magnesium and potassium has obvious effects on high yield and high quality.

When the plant has the symptoms of magnesium deficiency, the foliar surface can be sprayed with 3% 4% magnesium sulfate, and sprayed 3 or 4 times in the growing season, which has the effect of alleviating the disease. Magnesium sulfate can also be applied in a ditch in the soil, kilograms per plant.

Symptoms of boron deficiency in grapes: Leaves, shoots, and ovary can be manifested when boron deficiency. The tendrils near the tip of the grape before flowering turn black and appear to be nodular, swollen and necrotic.

The corolla does not fall when it blooms. The ovary forms seedless small fruit, shedding or not bearing fruit. The leaves mainly appear light yellow fading spots between the veins of the upper leaves or secondary tips or the leaf margins, and the severe cases are distorted or cause the leaf margins to be scorched, and the leaves fall early.

Occurrence rule: grape boron deficiency is a physiological disease, caused by a lack of boron, and the boron content (in the leaves) is less than 10 mg kg.

Control measures: (1) Improve the soil and increase the application of organic fertilizer.

2) When applying basal fertilizer in spring, apply kilograms of boric acid or borax per 667 m 2.

3) Borax solution sprayed during the growth phase.

When the grower encounters a problem, he asks Xiaoyang, who judges it as a boron deficiency.

Symptoms of potassium deficiency in grapes: In the early stage of potassium deficiency, the middle leaves of the developing branches first show a lack of green between the leaf margin and the midrib. When the potassium deficiency is severe, necrotic spots are produced on the old leaves, sometimes the necrotic spots fall off into perforations, the leaf margins turn yellow and then scorched, at this time, the leaf veins of the young leaves lack green, the leaf margins are scorched, the leaves become brittle, and the fruits are not ripe and uneven.