Potassium plays a key role in the late stage of grape fruit growth and development. It not only maintains cell swelling, promotes auxin synthesis, and ensures normal fruit swelling, but also contributes to the formation of endogenous substances such as sugar and acid to improve fruit quality. So, what are the symptoms of potassium deficiency in grapes? How to apply on grapes?
What are the symptoms of potassium deficiency in grapes
Grapes require a large amount of potassium. In recent years, the phenomenon of potassium deficiency in grapes is more common, which has a relatively large impact on the yield and quality of grapes. The symptoms of potassium deficiency in grapes vary with the growth and development stages of the leaves. In the early stage of the growing season, the base leaf edge chlorosis and yellows, the leaf edge produces brown necrotic spots, which expand and develop into the intervein tissue, the leaf edge curls and droops, the leaf is deformed or shrunk, and the leaf edge tissue is necrotic and scorched in severe cases, or even The whole leaf is dead. At the end of summer, the surface of the old leaves at the base of the shoots turned purple-brown to dark brown under direct sunlight, which is the so-called "black leaves". The black leaves begin at the beginning of the leaf veins, and if they continue to develop, they can spread to the entire leaf surface. After the plant is injured, the leaves are small, the branches and vines are stunted, the fruit is small, and the sugar content is reduced. The entire plant is vulnerable to freezing damage or infection.
How to apply on grapes
Common potash fertilizers include potassium sulfate, potassium nitrate, potassium dihydrogen phosphate, organic potassium, biological potassium, potassium humate, potassium fulvic acid, etc. The first five are the most common and most commonly used. In addition, plant ash is also a very good potash fertilizer.
1. Potassium sulfate: theoretically containing 54% of potassium oxide, generally 50%, while containing 18% of sulfur, chloride ion content ≤ 3%, the fertilizer effect is long-lasting; potassium sulfate is a chemically neutral, physiologically acidic fertilizer, with good Water-soluble, but long-term use will aggravate soil acidification. It is suitable from the late stage of grape coloring to fruit ripening period to promote fruit powdering and coloring and increase fruit sweetness.
Generally speaking, potassium sulfate is suitable from the late stage of grape coloring to the ripening stage of the fruit to promote the powdery coloring of the fruit and increase the sweetness of the fruit.
After potassium sulfate is applied to the soil, the soil will be acidified quickly, the more the application, the more serious the acidification. The acidification of the soil causes the root system of grapes to fail to grow, and the activity becomes weak, and it is not conducive to the absorption of calcium, magnesium, zinc and other elements by the root system. Therefore, the dosage of potassium sulfate should also be appropriately controlled.
2. Potassium nitrate: fertility is neutral, belongs to the chlorine-free potassium-containing nitrogen-containing potassium fertilizer (containing 46% potassium, 13.5% nitrate nitrogen), with the characteristics of medium price, high potassium content, strong instant dissolution, and quick effect. It can not only supplement potassium but also nitrogen, it is more suitable for topdressing, and it is not easy to acidify the soil; because it contains nitrate nitrogen, it will cause fertilizer loss when used in paddy fields, and it is easy to cause excessive fertilizer use or use in the coloring period. Crop maturity is delayed due to excessive nitrogen fertilizer. Potassium nitrate can be used in the growth period when the crop requires a large amount of nitrogen; in addition, potassium nitrate can be used in the normal crop growth period and fruit expansion period, but potassium dihydrogen phosphate is used in the flowering and fruiting period, especially the fruit coloring period.
3. Potassium dihydrogen phosphate: contains 52% phosphorus pentoxide and 34% potassium oxide. Potassium dihydrogen phosphate is a chemically acidic, physiologically neutral fertilizer with good water solubility. Generally before and after flowering, it can be used to promote root germination and flower bud differentiation, and provide energy for flowering and fruit setting; use in the coloring period can promote powder coloring and increase fruit sweetness.
Phosphorus in potassium dihydrogen phosphate is one of the constituents of grapes to form glucose phosphate and many coenzymes; potassium in it can increase the intensity of photosynthesis and promote the formation of starch and sugar in grapes.
Potassium dihydrogen phosphate can be used during the coloring period of grapes to promote flouring and coloring and increase fruit sweetness. Use after fruit picking can promote the aging of branches and increase the degree of fruit lignification.
4. Potassium humate: It is a kind of slow-acting organic solid potassium fertilizer. It is alkaline in fertility. Because it contains humic acid with strong biological activity, it has very strong adsorption, complexation and chelating properties, which can increase the soil. While quick-acting potassium, it can also reduce the fixation and loss of potassium in the soil, and promote more effective absorption and utilization of potassium by crops. It has good effects on activating the soil, promoting crop growth and resistance, especially for composites. Potassium humate can also provide crops with a variety of nutrients such as nitrogen, phosphorus, potassium, organic matter, and medium and trace elements, and can be widely used in basal fertilizer, top dressing and foliar spraying of various crops.