What are the control methods for acid and alkali damage in flowers?
I. Soil pH affects nutrient availability
Soil pH affects the solubility of mineral salts, and therefore affects nutrient availability. When soil pH is between 6 and 7, it is most favorable for plants to absorb and utilize nutrients. In strongly alkaline soil, elements such as iron, boron, copper, manganese and zinc are easily fixed, and in such soil acid-loving flowering plants such as camellia, rhododendron and gardenia will develop leaf yellowing and poor growth due to iron deficiency. In calcareous soil with a pH of 7.5, the combination of phosphorus with calcium reduces the available phosphorus content. In acidic soil, it is easy to cause deficiencies of elements such as phosphorus, potassium, calcium and magnesium, and in rainy areas there may also be deficiencies of trace elements such as boron, zinc and copper, which is extremely unfavorable for plant growth. Soil pH can also affect the activity of soil microorganisms and the role of humus, thereby affecting nutrient availability and the normal growth of flowers.
II. Adjustment of soil pH
1. Lowering soil acidity
Apply quicklime; the application rate depends on soil acidity, with 20-50 kg applied per mu.
2. Lowering soil alkalinity
(1) Apply sulfur powder. The application rate depends on soil alkalinity, with 1-3 kg applied per 100 sq m.
(2) Apply aluminum sulfate (white alum). If the pH value needs to be lowered from 7 to 6, 0.5 kg of aluminum sulfate can be applied per 100 sq m.
(3) Water with alum fertilizer water. For flowers that prefer acidic soil, watering with alum fertilizer water gives better results. To prepare alum fertilizer water, generally use 2-3 kg of ferrous sulfate, 5-6 kg of oil cake or soybean cake, 10-15 kg of human excrement and urine, and 200-250 kg of water, place them in a large vat, expose them to sunlight for 20-30 days, and after decomposition, dilute with water before application.
(4) Apply humic fertilizer. Humic fertilizer contains more humic acid, which can adjust the pH of the soil and transform it toward neutral.
Among the above methods, applying sulfur powder is the most lasting, but it takes effect slowly; when applying aluminum sulfate, phosphate fertilizer needs to be supplemented. Applying alum fertilizer water takes effect quickly, but its effect lasts a short time, so it needs to be applied frequently.
III. Control of acid and alkali damage in flowers
1. Control of acid damage in flowers
During the growth process of flowers, the root system continuously secretes acid, or acidic or physiologically acidic fertilizers (ammonium sulfate, ammonium chloride) are applied over a long period, causing soil acidification. For flowers that prefer neutral or slightly alkaline conditions, if the soil acidity is excessive, acid damage is easily caused, hindering root growth and causing poor growth of the aboveground parts. For this, alkaline fertilizers such as lime, limestone powder and plant ash can be applied to lower soil acidity, and generally 1-2 applications can achieve obvious results. The application rate of plant ash is 50-100 kg per mu, and it is the most effective potassium fertilizer.
2. Control of alkali damage in flowers
Camellia, gardenia, cyclamen, crabapple, rhododendron, magnolia and others are acid-loving flowers. Because they have long grown in an acidic soil environment, they are more adapted to soil conditions with high iron, high aluminum and low salt. Once planted in slightly alkaline and calcareous soil, or watered over a long period with water containing more calcium and magnesium, with a pH value of 7-8.5, phosphoric acid reacts with calcium to form various sparingly soluble calcium phosphates, reducing the availability of phosphorus. At the same time, ions such as iron, manganese, copper, zinc and boron can form hydroxide precipitates, reducing solubility and hindering the absorption of these elements by plants, thus causing deficiency symptoms.
When acid-loving flowers are cultivated in alkaline or slightly alkaline soil, the soil and irrigation water must be improved. For open-field flowers, generally 0.25 kg of sulfur powder or 1.5 kg of ferrous sulfate is applied per 10 sq m, which can lower the pH value by 0.5-1.0 (for heavy clay soil, the application rate should be increased by 30%). For potted flowers, a culture soil mixed with 1 part river mud, 1 part leaf mold and 1 part coarse sand can be used, and 0.5-1.0 g of sulfur powder or 1.5-2.0 g of ferrous sulfate is applied per kg of soil, mixed evenly and left to stand for 2 weeks before use. If water containing calcium and magnesium is used to water flowers, to prevent alkalization, a 0.2% ferrous sulfate solution can be used for regular irrigation. For acid-loving flowers, acidic or physiologically acidic fertilizers such as potassium nitrate, ammonium nitrate and superphosphate should be applied, and alkaline fertilizers such as ammonium bicarbonate should be avoided.