symptom
Magnesium deficiency is a common deficiency in vineyards. It mainly occurs from the old leaves at the base of the plant. The chlorosis between the veins of the first leaves develops into yellow spots between the veins after the leaves. Most of them spread from the inside of the leaves to the edge of the leaves, causing yellowing of the leaves. The mesophyll tissue is necrotic, leaving only the veins to remain green with a clear boundary.
Symptoms are not obvious at the early stage of growth, and gradually become more severe after entering the fruit expansion stage. Plants with a lot of fruit setting will have a large number of yellow leaves before the fruit is mature, and the yellow leaves generally do not fall early. Magnesium deficiency has little effect on fruit size and yield, but fruit coloring is poor, ripening is delayed, sugar content is low, and quality is reduced.
Etiology
Magnesium deficiency is a physiological disease, mainly due to the lack of replacement magnesium in the soil, and the lack of magnesium supply in the soil due to insufficient organic fertilizer or poor quality. In addition, magnesium is easy to lose in acidic soil, and too much potassium application will also affect the absorption of magnesium, resulting in magnesium deficiency.
Prevention method
(1) Every year after leaf fall, furrows are opened and high-quality organic fertilizers are applied, and the amount of potassium fertilizers should be appropriately reduced in vineyards with serious magnesium deficiency.
(2) When magnesium deficiency begins to appear in the grapes, spray 3% to 4% magnesium sulfate on the leaves, once every 20 to 30 days, and spray 3 to 4 times in total, which can alleviate the symptoms.
(3) For soils with severe magnesium deficiency, magnesium sulfate should be mixed with organic fertilizers, 100kg per mu. Magnesium sulfate can also be applied by ditching, 0.9-1.5kg per plant, and applied continuously for two years. You can also dissolve 40-50g of magnesium sulfate in water and inject it into the trunk.
(4) Adopt formula fertilization technology, solve the nitrogen, phosphorus, potassium and magnesium fertilizer formula more reasonably, and achieve scientific fertilizer use. Slow down the occurrence of magnesium deficiency.
